RV Tank Sensors &The GEO Method

Working tank sensors….pricelss :)

Almost every RVer I know complains about their tank sensors. It’s almost a given that after a few months the sensors start acting up and giving false readings showing tanks that are full when they are really empty. For anyone who dry-camps alot this is kinda annoying, and most end up just “living with it”. But there is hope! We’re not tank wizards by any means, but in 2 years of RVing we’ve managed to keep our black tank sensors working perfectly with our grey sensors OK most of the time. And most of it is thanks to the GEO method.

Typical tank sensor set-up. From dmbruss.com
Typical tank sensor set-up. From dmbruss.com

Now to understand why tank sensors go bad it’s worth understanding a little about how they work. Most RV tank sensors are basically just 4 screw probes that stick into the tank. When liquid hits the screw it makes contact & completes a circuit that turns the LED light on your panel on. Over time crud and slime covers the screws causing connectivity when there really is none (so sensors “think” the tank is full even if it’s not). It’s a really poor system, but it’s a cheap one which is why it’s so widely used. So, the key to making these things work again is simply to clean off that grime. Easier said than done, right?

Horst Miracle Probes -> a great little sensor upgrade
Horst Miracle Probes -> a great little sensor upgrade

There are a ton of cleaners, tank chemicals and what-not out there each of which have their passionate supporters. Also there are much better sensors such as Horst Miracle Probe and SeeLevel, both of which get excellent reviews. But for those of us with old sensors and a cheap pocket, this is the method that’s worked best for us:

1/ Never Dump Until Tanks Are At Least 2/3 Full

Waiting until your tanks are full before dumping helps keep things liquid and pressure high so that when you finally pull the plug “stuff” comes out rather than drying out and building up as pyramids in the tanks. So, even when we’re fully hooked-up we keep our tank valves closed until we’re ready to dump.

2/ Dump Black First, Then Grey

Always dump your dirtiest (black) tank first before dumping your grey. For those of you not in the know, the black tank contains run-off from your toilet, while the grey is run-off from your shower and sinks.

3/ Use Lots of Water & Back-Flush

Using lots of water (when you can) really helps to keep things flowing in the tanks. We’ve got a factory-installed back-flush system in our black tank and after we dump we’ll usually back-flush and re-dump before heading out again. There are after-market back-flush systems that are super-easy to install and work very well too.

4/ Clean With The GEO Method

The GEO method ingredients

The GEO method is a home-made cleaning technique that’s been around in the RV community since (at least) the early 80’s. Where the name came from no-body seems to know, but the original method is HERE. The original formula uses chlorine, but that can ruin your valves so these days most RVers use a slightly modified method with just 2 common items, both of which you can get at any big department store:

  • Calgon Water Softener -> This stuff helps to break down water surface tension, clean scum and prevent hard mineral deposits. I’ve used Borax on occasion when I can’t find Calgon and find it works just as well.
  • Dawn Dishwasher Detergent -> The “original formula” blue detergent is excellent at cutting grime. Laundry detergent works too.

After you dump pour 1 cup of Calgon and 1 cup detergent into the tanks. Leave them in until your next dump. Before driving some RVers will also throw a bag of ice-cubes down the tank to “scour” their walls (we’ve never done this, but others swear by it).

And that’s really it! We don’t use the GEO method each time we dump, but just whenever our sensors need an extra cleaning. Either way it’s a simple, easy and environmentally-friendly method to keep sensors mostly clean. And in a moving house on wheels that’s really as good as it gets.

What tricks do you use?

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We LOooVE Comments, So Please Do

  1. says

    The only ‘trick’ I use is keeping track ! LOL I found the readings when I had the Class C were fairly accurate based on my usage and the last time I emptied. But with the Class A they are way out. Even after I dump they show full.
    I have used the ice cube trick but only because I’ve read online that it is a good thing to do. No idea if it really helps.
    So I keep a record of when the tanks are done and how many days I can go without having to dump again.
    I’ve recently purchased “Happy Camper” as it’s supposed to be great for liquefying everything.

    • libertatemamo says

      Happy Camper is a good additive. We’ve used it over the past few years in the addition to the GEO method. Not sure how much it helps (or whether it’s any better than other additives), but they seem to offer a good product and we’ve always been happy w/ the results.

  2. Dan and Pat says

    If you want an eye opener, opt for one of the clear plastic connector elbows for dumping your black water tank. This simply connects to the discharge for your tank with your waste hose connecting to the other end of the elbow. I know, not what you wanted to see but you will find that even that first back flush doesn’t run clear. This is telling you that more back flushing is needed. This would be a great way to see what results you are getting from the GEO method.

    • libertatemamo says

      The clear plastic elbow is a FABULOUS addition and one I forgot to mention in the post. YES, definitely a simple, cheap and very useful add-on.

  3. says

    My Paul understands the first part of the blog. I understand the steps of dumping. We do exactly as you suggest. It really is very simple but some RVers get in a hurry and don’t follow the steps which leads to trouble. Good job explaining how to keep the tanks working properly. ~wheresweaver

      • Bill Montgomery says

        I followed your suggestions to the letter and the GEO method did not work. I then realized that there may be a few letters missing after you add the Calgon and Dawn – A-D-D-W-A-T-E-R. Tried it again with water and hope it works this time. Thanks for the info.

        Bill from Castle Rock, CO

        • libertatemamo says

          Yes, water is critical. That’s why I recommended you pour in the calgon & detergent and leave them in there until your next dump (i.e. until the tanks are full again). But appreciate making it clear for others who might have missed that detail :)

  4. Jerry B. says

    I’ve had probably 5 RV’s over the years and I don’t think any of them have had the sensors work properly, at least not consistantly. I do use the Geo method most of the time and it works well. One problem I’ve found it trying to get the Calgon liquid. Seems like it has to be a Walmart or similar and in a rural area where the water isn’t the greatest. I haven’t found it anywhere in my SF Bay area, had to order it on line from Drugstore.com. Maybe I’ll do the Borax next time.

    • libertatemamo says

      You’re right about finding the Calgon. Seems to be real easy to pick-up some places and completely non-existent in others. That’s why I sometimes substitute with Borax. It’s the same basic principle…laundry booster & softener…and seems to work for us.

      • Charles says

        If you can’t find the Calgon liquid then use Calgon powder. Add a cupful to a gallon jug with a litle vot water to dissolve then fill rest of jug with water and pour in tank. I also use powdered laundry soap. Works great for me. Use every other dump, and don’t need to add other chemicals to control smell.

  5. Luke Alexander says

    I put in a SeeLevel system about 5 years ago and love it. Always accurate because the sensors are on the outside of the tank. Easy to install. It was pricey, but ammortized over the years, it is well worth the money. I duct taped the sensors on, so I can move the system to a new coach as needed.

    • libertatemamo says

      I have heard SO many good things about the SeeLevel system. Every RVer I know that’s installed it loves it. It’s not really top of our list of potential mods, but may make it on there sometime over the next few years.

    • Victor Caceres says

      Luke, what SeeLevel system/model did you get for ur RV? We’ve only had our RV since April 2013 and the sensors are already reading incorrectly. Nina, thanks for info on GEO method.

  6. says

    I also added the SeaLevel system almost two years ago. Worth every penny. Works flawlessly and very accurate.

    We use enzymes that are similar to the stuff you put in home septic tanks. Environmentally sound. I use in both the black and grey tanks. Got the solid tablets at Quartzite this year. Maybe a little more than the “GEO” system, but my guess would be more effective. With the enzymes they eat the smelly stuff in the black and grey tanks continuously so no smells.

    I had never heard of the GEO system until I read this blog today.

    • libertatemamo says

      I’ve talked to several RVers who go the enzyme route and swear by it. The enzymes are targeted more for septic tanks than holding tanks, but I could see them helping if you manage to leave them in there long enough (several weeks) before dumping. Might look into it someday if my GEO method stops working.

  7. says

    This is coming from someone who no longer owns an RV, so any rolling of the eyes is perfectly understandable.
    Just the same, I think I must have read the Geo method years ago, and coincidently just came across it again the other day. I never had problems with our sensors (in the motorhome that we no longer own *sniff*) since I discovered early on that my grey water was filling up way too fast.. Had to come up with a way to divert liquid if at all possible.
    So I started using those plastic dish pans that fit nicely into each of our sinks, which then turned out to serve two purposes. First of all the sinks were being protected from the inevitable scratching and bumping that occurs during the wash up, and then I would dump the soapy water into the toilet. The soap obviously was helping to keep the sensors well lubed, and I was keeping extra liquid out of my grey tank. Simple.
    Only thing was though, it’s really important to make sure all the utensils are out of the soapy water. I’m pretty sure I lost a knife once down the poop chute. Didn’t see it go, but the count came up short not long after that. Your mileage may vary.

    • libertatemamo says

      Re-using the grey water in the toilet is a great little tip (and one we’ve used ourselves on longer boondocking trips). A nice water-saving idea and another way to get soapy cleaner down the toilet. Appreciate the tip about making sure the utensils are out beforehand tho’…LOL :)

  8. says

    Another great post – thanks!! Our black tanks are great but our gray need some help. To another of your comments – Happy Camper is great stuff, a guy who cleans tanks for a living did a seminar on it at a campground we were at and he loves that stuff. We have also used the organic tablets which are good too. Anyway, thanks!!

    • libertatemamo says

      Yup, we’ve also used Happy Camper and like the product. Pretty much stick to that and the GEO method for our tanks.

  9. says

    Our gauges work well in the older Country Coach we have now, they never worked in any of the other RV’s we owned. I started using the Calgon and detergent about a year ago just to make sure the gauges kept working. Do you also use some type of holding tank chemical or just the Calgon and detergent?

    • libertatemamo says

      Great to hear the GEO method is working for you! We’ve used Happy Camper in the toilet too, but I’m not sure it’s strictly necessary. At this point it’s probably more habit than anything else. Between the 2 methods our sensors keep clean so we haven’t messed with it.

  10. Susan says

    Thanks for the great information.. it could not have come at a better time. Recently, I have been having difficulty with the sensors accuracy and I will definitely put your suggestions to work. Once damage occurs is it reversible over time with better tank care? We have enjoyed our winter of travels and sadly must head back North once again. We learned alot from following your blog and the old “trial and error” so hopefully next year will be a bit easier.

    • libertatemamo says

      I do think it’s reversible, but it all depends how “solid” the crud is on the sensor screws. I’d try the GEO method several times for sure (never hurts). If that doesn’t work and you’re going to leave the RV sitting around for a while I’d dump some enzymes (the type used in septic tanks) to see if they can help digest things down there. The enzymes need time to work, so let them sit for several weeks or more in a full tank before you dump.

  11. Joyce Samples says

    We’ve been RVing about 5 years now and I never heard of the GEO system. I plan on trying it. We have a motorhome and the tanks always show full. Ours does sit most of the time in an RV park and has not been driven much in the last 2 years. I assume that maybe that has something to do with it. I feel like if your moving maybe that helps things get worked out better? Just wanted to say I enjoy your blog very much. Always look forward to it showing up in my email.

    • libertatemamo says

      I do think moving around helps to slosh things in the tanks and mix ’em up. We usually try to leave the tanks partially full for our drives so we can get that cleaning action going on the road. Also, if you’re leaving your valves open while hooked-up that could be another reason for sensor build-up. Closing the valves and only dumping when you’re full really helps IMHO.

  12. Jerry B. says

    One more comment, our tanks are NOT septic tanks which need to “digest” and they usually only hold the contents for maybe a week at the most and more often just 3-4 days, so I don’t see the advantage of digester/enzyme types of additives. The soap and water softener work well for us and are environmentally friendly and we don’t have any odor issues. Part of the key is using enough water to keep everything liquified and just dump a little more often. Just my opinion…

    • libertatemamo says

      I do think water and keeping things moving is KEY! I could see enzymes potentially helping if you’re leaving the RV sitting around for a while (several weeks or more), but I’m pretty much with you on the water, soap and calgon approach.

    • Dav says

      I’m totally new to rving….. Do you add GEO mixture to BOTH tanks and then add water to each tank? If so, How much much water? Thanks in advance!

      • libertatemamo says

        Yes, you can use it in both tanks. I typically add the GEO, allow the tanks to fill, drive to the next site (to allow it to slosh around) and then dump. If you don’t want to wait for it to fill you could simply add several gallons (say 5-10?) of water and do the same.


  13. Sheila says

    Thank you for the info on the tanks. I printed your post, and it’s going in our “truck book” along on our next road trip. While we’re on the subject of tanks, do you have any advice on the propane tanks? Is there any way to know how much gas is left in the tank?

    • libertatemamo says

      We’ve been struggling w/ the propane issue ourselves and haven’t found a solution yet. We kinda know how far we can go on a tank, but we’ve gotten darn close to zero several times without knowing it and our propane sensors are useless. I’m going to try Linda’s idea w/ the water. If it works that’s a keeper!

      • Ron Peterson says

        I Pour a pint of hot water over the tanks. This will show a frost llne on your tank which then show you the propane level in each tank. And where out camping I leave both of my tanks turned on. This will help you determine that you have plenty of propane flowing if one tank runs out the other tank will switch automatically so your refrigerator and water heater will keep running without your appliances pilot lights going out. You will have plenty of Hot Water when you need it, you won’t have warm a spoiled food.

        • libertatemamo says

          The hot water trick is a sound one. We only have one large propane tank in our class A, but for those with two tanks the other tip is a good one too. Cheers for sharing!


    • ML says

      With our propane tank on our BBQ we boil the teakettle and pour it over the side and feel down the tank with your hand and the cold part is where your propane is, I don’t know why that wouldn’t work with the big tank on your RV.

      • libertatemamo says

        Yup, that’s a great tip and it works! Since I wrote this post we’ve used the “hot water” method many times for our big tanks. It’s not perfect, but it gets pretty close.

  14. lwdrene says

    Sheila, we wrote about how we measure our propane usage for our 5th wheel in this blog post.

    As far as what tricks do we use to tell when our tanks are full? None, we just wait until we smell it! Hahah. Well sorta. After 5 years of fulltiming we know how long we can go with our current setup. Still, it’s annoying to see those worthless sensors read “full” when they’re not.

    We need to try the Geo method. I’ve read about it so many times but have been too lazy to try it. Thanks for the reassurance that it actually works.

    • libertatemamo says

      Rene, Can you re-post the link to your blog post on propane (it didn’t come out)? I’m interested too!

  15. Linda Sand says


    If your propane tank is external–you can see it–just pour a cup of hot water down the side. You will get condensation where there is still propane so that line will tell you how full it is.

  16. Wayne says

    I’ve given up trying to keep sensors working and havn’t had much success with commercial cleaners or the geo method. I have been full timing for 6 years and generally I’m hooked to a sewer or septic. My “sensor” is watching for a bubble of air to come up through the liquid going down the toilet. This indicates the liquid level is above the vent pipe in the top of the holding tank. i leave the gray tank valves open or would be dumping gray water every other day. When i see the bubble i close the gray valve for a couple showers to flush the black water dump. For the two of us i usually have 2 or 3 days before the black tank starts to backup into the toilet. I can usually go a couple weeks between black water dumps.

    • libertatemamo says

      We’ll usually hear the toilet “burp” too when it’s full. If I’ve been lax on checking the sensors I’ll know by the noise that we’re getting close and need to dump.

  17. Dave says

    We were thinking of using the bag of ice idea to clean our tanks and were told by an RV repair tech. that there is the possibility that when the ice is sloshing around it could knock the sensors off of the tank.

    • libertatemamo says

      Unless you have nicer/longer probes in your rig (e.g. something like the Horst Probes), the regular ones are just short, thick screws which I can’t see being affected by ice-cubes. I guess it would be possible to damage them or knock them out, but I’d think it low probability. Still…it’s good to share the warning. You never know…

  18. says

    Being long time boondockers, we like to dump at the free (used to be free) sites at Flying J. We buy a small bag of ice right before we leave and dump it in the head. Going down the road it knocks any “chunks” out of the corners and keeps the probes clean. We can go 14-20 days between black dumps.

    • libertatemamo says

      We usually go around 2-3 weeks between dumps too. When we’re hooked-up we’re more liberal with our water, but when boondocking we stretch it to the max :)

  19. Sue says

    This isn’t a comment on your “black tank” tricks, although we find them very helpful! We’re about to embark on a year’s adventure in our motorhome with our two large dogs (standard poodle and lab). My question is what do you use for Polly’s tick protection. Our dogs are black and I find it very difficult to simply pick them off, or find them for that matter! Do you use a tick collar? thanks for any information.

    • libertatemamo says

      Polly is sensitive to just about any chemical so we don’t usually use any tick prevention unless it’s absolutely necessary. We carry around some Frontline that we’ll use if we’re going into a particularly bad area. Otherwise I just search her fur (which takes time!). If you need to use it I’d advise using a monthly topical application like either Frontline or Advantage rather than the tick collars. There are also natural alternatives (e.g. essential oils) which can work.

      • Sue says

        I do use a topical monthly, but the vet suggested adding a tick collar too and I wondered what you did. Its so difficult to see anything in that dark black fur that i’m concerned I’ll miss one and risk lyme disease for them, or us, for that matter! I guess we’ll just see what happens!

        • libertatemamo says

          Yeah I’ve never liked the collars. Seen too many issues of toxicity with them. If you need it I think the monthly topical is more than enough.

  20. Kay Leamon says

    We bought our A class new in 2007. The dealer recommended “Unique”. We have always used Unique and our sensors have always worked. We met another RV’er who had sensor problems, told them about Unique, they have not had sensor problems since. We also are very careful about cleaning our dishes, utensils and pots and pans with paper towels so the food does not go into our gray tank.

    • libertatemamo says

      I’ve heard good reviews on Unique (RV Digest It) products from others too. Wiping off pots and plates before cleaning is a good tip and one we use too. Better to keep the grease out of the tanks.

  21. says

    Great post Nina! I’ve never seen a poll done, but I wonder if most folks with tank sensor problems are those who always use hookups and leave their valves open, don’t backflush their tanks, and use every wiz-bang product CampingWorld sells to try and “fix” their problem! Glad I listened to some sage RVers when I first bought my coach who taught me your first 3 steps above, and also advised that if I always followed them, no extra deodorizers or tank enzyme cleaning products would be necessary. After 3 years, I’ve yet to have any problems! My coach didn’t come with a backflush system pre-installed, so I use a FlushKing adapter and created this step-by-step blog post of how I use it: http://bit.ly/GQv6gO

  22. says

    Great tips! In California some of the RV parks we have pulled into have their own required cleaners. To each their own, but the GEO system sounds about as simple as it can get. We rent towable travel trailers and are looking for the tried and true systems that work. Thanks for the advice! The only thing we can’t really comply with is not emptying the tank until it is about 2/3 full. We flush dump and clean after every rental.

    • libertatemamo says

      Have to admit I haven’t come across the required cleaner deal anywhere we’ve stayed in CA. Interesting to know.

  23. George and Brenda says

    Great BLOG. My wife Brenda got me hooked on your site and I check it out about once a day. I may finally get thru all of your posts. LOL The GEO method is one of the items that I will add to my growing maintenance list. Does GEO stand for GET EVERYTHING OUT? Well maybe not.

    Although we have camped through out the years from tents, to a small trailer and 5th wheel, we plan to start full timing in 2014 once our home sells. We plan to buy a MH and do some boondocking and the rest in some type of RV park.

    Keep up the great postings and hope to see you out there down the road.

    • libertatemamo says

      Yup, it stands for Get Everything Out…at least that’s what I’ve read as the “official” translation :) Happy you like the blog and good luck with your up-coming fulltiming plans. We sure love the lifestyle, as you can see.

  24. LP says

    After you add the Dawn & Calgon, do you then use regular toilet chemicals for the next camping trip? Or add more soap and softener? I’m desperate for something that will get the stench out. Bleh!

    • libertatemamo says

      Yup, after the Dawn and Calgon treatment (assuming it’s worked) we go back to regular toilet chemicals. Now, if you have a stench I wonder if there’s something going on with your vents? Have you checked to see if they are clogged? The toilet seal should keep everything “in the tank” and the vents should release everything “smelly” outside.

      • LP says

        Thanks for the tip! Will check the vents. To be clear, we can leave this solution in the tank with waste until it is time to dump…in lieu of typical additives. Then we empty as usual and use other treatments?

        • libertatemamo says

          Actually a better alternative, if tanks are very dirty, is to put in the GEO solution, fill with regular water and then drive around. Kinda like doing a washing cycle in your RV tank. Then dump and go back to your usual method. You can do this “washing cycle” several times until you’re happy with them results.

          • jdubya says

            LP: we have used the GEO method for several years and find that it works well to reduce odors and keep the tanks clean. We use it every time we dump until we put her away for winter, when I dump and add rid-x instead of soap and calgon. We use the camper at Christmas when the kids visit so we don’t winterize per se. In the spring I dump, flush and reinsert the GEO ingredients and use it all summer after each dump.

            BTW: I am not saying anything about the method libertatemamo suggests – sounds like it will also work well.

          • libertatemamo says

            Good tips! Thanks for sharing your ideas on this. I’ve heard many folks use Rid-X or other septic tank treatments (e.g. RV Digest It) with good results.

  25. LP says

    My eyes are being opened wide to the world of keeping a toilet clean! THANK YOU! Jdubya, you never, ever use chemicals until you put it away? I checked the bathroom this morning and I have no smell. The tank is almost full of water and the Calgon/Dawn mixture. We have to move it in a week or so to get it inspected, so that sloshing should swish it around well. I am such a novice! In my head everyone is supposed to use the chemicals b/c that’s what “they” say to do. The GEO ingredients are closer to my house, too. I can always find those at our local Kroger! I feel so enlightened! :o) THANK YOU!

    • jdubya says

      LP: not only that, but we just bought a used 2004 Fleetwood Flair 33R. We used it for a short time earlier this summer and put GEO in the tanks, but as we traveled this fall, the sensors went from working to not working in steps on mainly the black tank and we started to get odors in the camper. The sensors are the more expensive outside type that don’t get coated so I was mystified. I put twice the amount of GEO in as I normally used and as we left for home the tanks were quite full. By the second stop, the sensors started working again and no odors. I filled the tanks, ran the flusher, dumped and re-GEO ed it. When we got home it was still working and no odors. I think the GEO cleaned off the walls and fixed up the sensors in the process. BTW we use ALL and Calgon in the black, Calgon only in the grey.

  26. Nan says

    pay attention to what you put in your holding tanks when they are capped off..as in..when you make a potatoe salad and drain the potatoe water..and egg water ,,then finding a curdled bottle of homemade irish cream and dumping it down..then deciding to keep that pretty bottle for a refill so you happen to add baking soda in the bottle to soak it and you dump that..you then notice a geyser of fumes and bubbles..you commence screaming and your husband about breaks a leg trying to forgo the steps to get to the valve to release before it blows up..the horror you feel when it blows just as he releases and you split your holding tank..in a rv that is less than a year old..after finding a plastic binder glue for the holding tank you precede to the next stop and realise you will be trading in sooner than later ….

    • libertatemamo says

      Oh dear…sounds like you might be talking from experience here? That sounds like QUITE the little tank adventure…ouch!

  27. Diane says

    I am still a little uncertain about the proper way to use the GEO method. We have empty tanks right at the moment as we dumped before coming home but I am sure we need to clean them as the sensors were not reading correctly. We live in Chicago and didn’t want to leave water in the tank while it was still going below freezing here but now that we’re (hopefully) past that, we are going to go out and fill up the tank and add a cup of Dawn and a cup of Calgon and let it sit for awhile. THEN, we will drain it and rinse it out and add more water and Calgon. Does this sound like the way we should do it?

    • libertatemamo says

      I’d actually suggest adding Dawn, Calgon, WATER (very important) and then driving around for a while (e.g. to your next camping location). Ideally you want this stuff to be sloshing around in your tank. Then, dump when you’re ready. Make sense?

      • Diane says

        Thank you! That isn’t near as complicated as I was trying to make it! It will be interesting to see if this actually makes our sensors more accurate. Thanks again!!

    • libertatemamo says

      Yup…you can put in the stuff, drive around with it, fill it with waste and then dump. Or just put in the stuff, drive with it and dump. We like to wait until our tanks are full before dumping so the first approach is the one we usually take. Doesn’t really matter if the calgon/dawn is in there by itself or with waste. The key is just give it time in the tank (preferably with a bit of sloshing around) to work it’s magic.


    • jdubya says

      LP: That is exactly what you do – we never use anything but soap and softener. The softener keeps the solids from collecting on the walls and bottom of the tanks, and along with the soap keeps the stinky guys from growing.

      If you think that there is old material (solid waste) in the bottom of the tank, some have had success getting it out by dumping a sack or two of ice cubes into the tanks with only a few gallons of water and drove around, but there is no reason to do that otherwise. Rather than waste money on the expensive tank deodorizers, use the GEO method all of the time. And if you don’t use the coach all winter, consider dumping the tank, rinsing and putting a few gallons of water with rid-x in the tank through the toilet. You can still use the camper periodically if you wish, but rid-x won’t work with GEO in there, too. The rid-x will get hardened material that won’t soften otherwise.

      If the tank is already really bad (stinky) put a quart of clorox into the tank and fill it to the top. Then after letting it sit for an hour or so, drain it and refill at least partially, dump again without adding anything, and then put the GEO ingredients into the tank and leave it there. Use the camper, dump and put the GEO in again according to the GEO process, etc, etc. No need to use any other tank chemicals unless you really love to throw money down the toilet.

  28. says

    I have mixed results with the GEO method (with regards to sensor cleaning), but I have to say that I really love the smell of liquid Tide and Calgon .. Whenever I step into the bathroom, it smells like that. I use no other tank cleaners and use the GEO method for both gray and black tanks each time I dump, and it always smells fresh.

  29. jackfish says

    I have to advocate for Happy Camper. One ounce per 40 gallons of black tank capacity is about 70 cents for each fill/dump black tank cycle in my rig. It is dissolved into two gallons of water and poured into an empty black water tank. That’s it. With normal use of the toilet and bathroom sink enough water is put into the system for it to work. Happy Camper contains minerals and micro nutrients that lubricate the tank so it empties easily and helps keep the sensor working. The micro nutrients include aerobic bacteria that liquefy waste and kill anaerobic bacteria, the cause of foul black tank odor. I have had zero problems with dumping and odor since using it. My black tank sensor still works as well as it did when new.

    The GEO Method is more expensive, using more product and water, is harder on the environment, and when using the bleach component is actually counterproductive to a healthy black water tank system. If you want a happy black water tank system try Happy Camper, the name is apropos.

    For a poorly maintained black water tank which has difficult build up, proper use of the Happy Camper Extreme Cleaner will get it back into shape so one can begin black tank bliss with regular use of Happy Camper.

  30. Liane Goodrich says

    Love this blog! I have ordered calgon. I bought the only water softening product I could find, which is made by arm and hammer. It has to dissolve in hot water and is a pain. As for the dawn dishwashing detergent, that is my go to soap for home and in the coach. I recall it was what they used to clean birds after oil spills. I put it in the bathroom in a pump dispenser (diluted first) so every dishwashing or hand washing adds some dawn to the grey tank.

    Can sympathize with the folks with exploding tank. We went dry camping so I was really conservative with water and made a horrible smelly mess from vegetable residue on dishes and utensils. I even bought a little strainer basket (mesh, like a tea strainer) to catch all the solid residue. Eventually I discovered the anti siphon valve under my kitchen sink was bad. It’s supposed to equalize air pressure to allow the sink to drain. And then shut. My valve was stuck open. The smell was a combo of poop and rotten eggs. Horrible. That plus forest fire smell nearly drove us nuts driving home.

    I am not having black odors but black sensor issues. So I am GEO methoding black. I just wonder if my pseudo GEO is cleaning my grey out.

    Fingers crossed!

    • libertatemamo says

      Yuk on the blocked tank. We’ve had that happen once (before we figured out to wipe our dishes before washing them) and know what it’s like.
      Hope the pseudo-GEO works out for you!

  31. barrigoni says

    Thanks for all of the great information. We have been using Happy Camper but still having some sensor issues so will give the GEO method a try. Couple of questions:
    1. What are your tips for making 2-3 weeks between dumps when dry camping? My husband and I are new full timers and plan to be doing quite a bit of dry camping. So far it seems like we make it ~10-12 day’s before needing to dump.

    2. Have you ever considered a composting toilet?

    Appreciate all the invaluable insight:)

    • libertatemamo says

      Hi there,

      Regarding how to last longer on your tanks I’d suggest this post which I wrote a while back on conserving water. It has all the tips and tricks we use for our longer boondocking stays:
      Going “Water-Green” = Conserving Water on the Road

      As for a composting toilet I’ve looked at them and I really like the way they break down the solids into a natural form, but I don’t want to have to deal with buckets of pee. The latter seems a big pain and it’s probably the main thing that keeps us from seriously considering them. If I have to dump pee on a regular basis I’d rather just use my tanks and dump from my sewer hose every 3 weeks instead of having to lug around a bucket (in/out of the RV) and find a spot to do dump that every few days.


      • frosti1031 says

        My husband and I drove truck over the road for quite a few years before getting off the road. I love my little 18′ camper, it feels like home but with a kitchen and bathroom, and really spacious compared to a Peterbuilt 379 sleeper! We always delt with liquid waste in gallon sized Zip Lock freezer bags (it’s not worth it to get cheap and try and go generic or storage bag with this). We bought them in bulk at Costco, and disposed of them twice daily at fuel stops. I preferred to handle urine as little as possible. Any extra pouring, carrying, or handling is just an opportunity to spill. We would do our business directly into the bag (a little practice makes perfect), zip lock it, into the trash bag-lined 5 gallon bucket to await the next trash dump. I knew some women who used large cups or coffee cans and poured into sealed bottles but that just seemed messy to me. Too much rinsing, splashing, sloshing, spilling,etc. Another option is liquid absorbing gel or powder (like what is in diapers or clumping kitty litter), you should be able to find it at a janitorial supply store. It would convert your liquid waste to a solid waste for easier disposal.

        • libertatemamo says

          Good tips for those looking to dispose of waste without using their tanks. We used similar methods (e.g. The gels) for backpacking in areas where you had to pack-it-out many years ago. We are happy using our tanks and our black stretches 3 weeks between dumps when we’re boondocking, so we probably won’t ever need to bag up our waste, but for those in smaller rigs and/or with smaller tanks and not near hookups these tips are great. Cheers for sharing your experience.


  32. Ed Winn says

    I have problems with my sensors, And all the solutions I have read about require some type of additives while traveling down the road to slosh things around. I am stationary until i find a truck for my 5ver . My black tank has the Flush kit installed. My Question is has anyone tried flushing the tank with HOT! water to clean the sensors??

    • libertatemamo says

      I’ve never tried it, but we do have a back-flush on our tank and it works well when we’re sitting still for longer periods. You may need 3-4 good flushes before seeing results. Give it a go and let us know how it works!

    • libertatemamo says

      Yes, It’s good practice to keep them closed until they are at least 2/3 full before you drain. The black is more important then the grey. We’ll sometimes leave the grey open if we have hookups (especially if we’re using the washing machine and such), but we *never* leave the black open. Always let the black fill before dumping. This prevents buildup and ensures you have enough pressure to push the contents out cleanly hen you dump.

  33. Kara says

    Never heard of the GEO method but I will be trying it after our next trip. My black tank says full after a dump. Going to look into the backwash also. Thank you for the article!

  34. JLodge says

    I have heard from many forums that an alternative method of doing this is just replacing the sensor. I have heard of many using a SeeLevel sensor, as it is positioned outside of the tank and because of this, the grime can not accumulate and alter the readings. The only complaint I have heard with this system is that it is not waterproof, so if water comes in contact the system breaks down. Another option that some might want to consider is this . It is considerably cheaper and is also watertight, although I don’t know whether or not the wire will corrode.

    • libertatemamo says

      Indeed. I mentioned the See Level sensors in my blog post. I know many folks who use them and really like them. They’re a bit of an investment upfront and they can miss-read if your tanks are very gunked-up (happened to a friend of mine), but they suffer far fewer issues than the traditional in-tank sensor probes.


  35. says

    All the comments have been really helpful. I use my RV primarily for Dog Shows so I do 1-2 shows a month. Mostly I’m in it for three days sometimes five. How long is it OK to let the tanks sit between shows until they are full enough to dump? Or should I just fill with water after each trip and dump every time?

    • libertatemamo says

      Dumping 1-2 times/month is perfectly fine. We typically boondock & leave the tanks for 2-3 weeks at a time before we dump. The key is just to make sure the tank is at least 2/3 full (so, if it hasn’t been filled by “use”, add water to fill it up) before you dump.


  36. Jean says

    We just had the SeeLevel system installed and have only had 3 dumps since then. The grey tank worked great from day 1. I have always wiped everything off of dishes before washing them since we purchased the rig new in 2010.

    The black tank sensoring did not work as well. It had somewhat erratic readings. After much research, I found suggestions that perhaps there might be some residue stuck to the sides of the tank causing false readings when it absorbed moisture.

    We’ve always used a bacteria type treatment in the black tank and never had an odor problem. We’ve used the GEO method often along with the bacteria treatment, but the internal tank sensors never seemed to work.

    We just purchased the Happy Camper Extreme Tank Cleaner, dissolved the full container into hot water, poured it into an empty black tank, added about 15 gallons of water and added 2 large bags of ice, per the “for best results” directions.

    We then drove for 8 hours. After arriving at the campground, we filled the black tank up the rest of the way with water and let it set overnight.

    We will dump it in a few hours and see if all of this worked magic.

    I’ll post results afterwards.

    • libertatemamo says

      One of our buddies had the same problem with the Seelevel when he first installed them. He got a “deep cleaning” of his tanks from a guy in Yuma and that solved he problem. Hope the Happy Camper Extreme works out for you.


  37. Davene says

    I have a camper on a permanent site and use April thru October. I started using the GEO method due to an odor problem. After using this method for almost 2 seasons I continue to have the odor problem. I saw a post discussing checking the vent and was wondering what this entails and how to go about this. Thanks for any suggestions.

  38. Land Yacht says

    New to RVing. Great info from everyone. We’ll be trying the GEO Method.

    Thanks again. Happy travels!

  39. says

    Hi Nina,

    Hope you are enjoying Bend!

    Do you guys have any experience with Drainmaster valves for Gray and Black tanks, specifically the need to clean the valves on a regular basis? We have been on the road for almost 2 years now and had our gray tank valve stick in the open position while dumping & cleaning our tanks. We have had no issues until now. We called the manufacturer and they said that we should be cleaning the valves every 3 months if we are full time. Just wondering if you have heard anything about this and/or have any recommendations.

    Happy trails,


  40. Joyce says

    This is by far the best blog I have read! We just purchased our first travel trailer and love it. It’s brand new so everything is still under warranty. Our black tank keeps saying its 2/3 full when we know it’s not. Definitely going to use the GEO method. Even the comments from others on here have been very helpful.
    We are Happy Campers!

  41. Nancy says

    I read almost all the posts…if I missed this trick, my apologies. We save space in our black water tank by NOT throwing our used toilet paper down the toilet. Even though it will degrade, consider the volume the paper adds.We keep a small step-lid trash can by the toilet, lined with dollar store brand trash liners (small size). Remove and tie shut daily and dispose with your kitchen garbage. We can tolerate a two-day cycle, even boondocking in southern AZ/CA. Alternative: ladies, put peepee paper in this trash and flush the other. This will save a considerable amount.


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