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What is the Geo Method for RV Tanks?

What is the Geo Method for RV Tanks?

Most homes-on-wheels have an RV black water tank and an RV gray water tank. Keeping both of these tanks clean and in good working order is a priority. RV tank treatment and maintenance serve to prevent odors inside the RV living space and to keep RV holding tank sensors performing well so that we know when tanks need to be emptied. There are many ways to achieve these goals, but today we’re focusing on the Geo Method for RV tanks.

Many RVers swear by this RV tank treatment method, so let’s jump right in to find out why!

What is the Geo Method for RV Tanks?

The Geo Method is a manner of treating and maintaining an RV’s black and gray water holding tanks by using a combination of water softener, laundry detergent, plenty of water, and sometimes (but not always) chlorine bleach as a means of odor control.

Let’s take a look at exactly how the Geo Method is employed.

First things first – you’ve gotta dump the tanks. For a primer on how to do this, click on the video embedded below in which we offer instructions while dumping our tanks:

Directions for Using the Geo Method

Once you’ve thoroughly dumped and flushed your black and gray water tanks, you’ll want to follow these instructions to use the Geo Method: (We’ll note again that there are various methods people follow – we’ll include all of the most common products used in the following steps.)

  1. Dissolve two cups of water softener in a gallon or two of hot water. (Many people use the powdered Calgon water softener.) You’ll do this for EACH tank, so you’ll make two “batches” of this solution.
  2. Pour the solution into your sink or shower for the gray tank, and into the toilet for the black tank. The point of the water softener is to keep “stuff” (solids, toilet paper) from sticking to the sides of the tanks which is especially important for accurate monitor readings.
  3. Add a cup of the original blue Dawn dishwashing detergent or a cup of eco-friendly laundry detergent to the black tank. This helps to further clean and deodorize the black tank. (Note that some people also add some bleach to the tank at this time, particularly if they’re experiencing odors. Some RVers instead add ¼ cup of Borax to the black tank.)
  4. Use your tanks normally and empty them when they’re between ⅔ full to full.

Use the Geo Method as needed or every time you dump the tanks.

Pro Tip: Use a clear plastic elbow connector to attach the sewer drain line to the RV wastewater outlet.

Camco Clear 45 Degree RV Sewer Hose Adapter Fitting | Features 4 Bayonet Prongs, a Heavy-Duty Polycarbonate Construction, and is Compatible with 3-Inch Diameter Sewer Hoses (39432), Clear
  • Clear RV Sewer Hose Adapter: See-through hose adapter allows you to see when your RV sewer system is clean
  • Compatibility: Fits 3-inch diameter RV sewer hoses

We should note here that if you’ve got a foul odor in your RV and you suspect it’s the gray or black tank, go ahead and clean & deodorize your tanks. However, sometimes an odor requires a bit of sleuthing before the true culprit is identified.

For example, we had a foul gray water tank odor in our rig on a couple of occasions, and the issue wasn’t a gray tank in need of cleaning.

These are issues and solutions you should know about, so we’ll share them here.

Here’s what happened the first time we experienced a need for holding tank odor control:

The second time the culprit wasn’t quite as easy to track down!

And there are lots of reasons why an RV toilet can stink, so take a look at that post if you’ve got odors that don’t go away with the dumping, flushing, and cleaning of the holding tanks.

Does the Geo Method Break Down Solid Waste?

Well, technically the Geo Method isn’t intended to break down solid waste, but it can eliminate odors by successfully cleaning your tanks. And the method is successful for many RVers (which is why it’s a popular method).

The purpose of the Geo Method is really to rinse the waste down the line effectively and to keep holding tank surfaces free of gunk build-up.

One of the reasons why users of the Geo Method also recommend including laundry detergent or dish soap is to help with the breakdown of solid waste. While these products are helpful in breaking down grease, they’re not quite as good at breaking down solid human waste and paper which is necessary to avoid clogs.

Does the Geo Method Address Odor Issues?

The Geo Method may still not sufficiently address odor issues, which is why some users suggest the idea of using some bleach (or another type of chlorine) to address odors.

Bleach (and the Geo Method itself) kills bacteria which can address odor issues, however, this also has a downside.

Can the Geo Method Be Used With Bacteria-Based Holding Tank Treatments?

Because the Geo Method kills bacteria, it can’t be used with a bacteria-based holding tank treatment because it’ll kill the good bacteria in the treatment.

The water softener in the Geo Method raises the PH levels to the extent that good bacteria can’t survive in the environment. Powdered Calgon, for instance, causes a chemical reaction with hard water that raises the PH levels so high that it will pull calcium & magnesium from the walls of your tanks (and thus from your sensors which is good). But it will also kill off the good bacteria you use to treat your tank. So, there’d be no point in using it.

In fact, not only will the odorless good bacteria likely die off when the Geo Method is used (due to the high PH), but the bad (anaerobic) bacteria often survive in the environment. (These are the bacterias that cause a sewer-like odor.)

And if you use bleach to address odor issues as part of the Geo Method, that will also kill bacteria.

So, the Geo Method can not be used in conjunction with bacteria-based holding tank treatments.

Is the Geo Method a Good Option for Boondockers?

The Geo Method may not be the best option for boondockers, especially in very hot weather. Because the odor-fighting components of the Geo Method aren’t as powerful as traditional tank treatments, hot-weather boondocking may call for something stronger… or a second Geo Method dose.

Does the Geo Method Save Money?

It’s probably fair to say that if you’ve already got the ingredients for the Geo Method on hand you could save a little money. In truth, though, the cost of tank treatments is probably pretty much a wash (so to speak).

Have The RVgeeks Used the Geo Method?

We’ve actually used the Geo Method on and off over the past 20 years or so. In the end, while we know MANY people who swear by the Geo Method, it didn’t seem to work for us as well as our ultimate method of choice. Additionally, finding and storing/carrying all of the ingredients for the Geo Method proved to be far more troublesome than carrying a tub of Happy Campers which is our treatment of choice because it works very well for us.

Happy Campers RV Toilet Treatment 18 - Extra Strength Odor Eliminator for Black and Gray Holding Tanks
  • Powerful Odor Control: Say goodbye to unpleasant odors with our powerful formula that neutralizes and eliminates foul smells, leaving your RV smelling...
  • Effective Waste Digestion: Happy Campers breaks down waste and toilet paper quickly and efficiently, preventing clogs and ensuring smooth tank...

That said, in an ongoing effort to discover new and improved methods of doing just about everything on an RV, we’re currently testing something completely different, yet again. Stay tuned, because we’ll definitely post an update if we have something good to report.

It’s important to remember, though, that proper tank maintenance includes digesting waste, preventing or eliminating odors, and cleaning your RV tank sensors.

Oh – and don’t throw your money away using “special” RV toilet paper. Pardon the pun, but it’s a total waste!

Also, remember that struvite can build up over time in RV tanks just as it does in sewer lines. This means that no matter how clean you think you’re keeping your RV holding tanks, you may eventually need a professional clean-out as we did:

Have You Used the Geo Method for RV Tanks?

So, tell us – do you use (or have you used) the Geo Method to keep your RV tanks clean? Drop us a comment to let us know how it has worked for you.

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Jesse Crouse

Sunday 9th of June 2024

We have used the Geo Method the past 4 years with no odors and no clogs. Very happy with it.

Jennifer Sadugor

Saturday 3rd of June 2023

I am here in California so I am not able to order the Happy Campers RV Tank cleaner. Do you have a second choice? Right now, I do use the Geo Method with 20 Mule Team Borax, Dawn dish soap and lots of water. It seems to be working but would be good to have other choices. It was recommended to use Citrasolv in the grey tank from kitchen sink to help cut the grease. I have not tried that yet. Any suggestions would be appreciated. I love this blog...Thank you for taking the time to post info to help us all out.

Jennifer Sadugor

Sunday 4th of June 2023

Thank you for letting me know. I will order some...I will try the PineSol instead if that is easier on the seals. I would have diluted the Citrasolv...It has been hard to I do not have any yet...Thanks again Your posts are excellent...


Saturday 3rd of June 2023

Hi Jennifer. Our second choice would be Unique Clear-It (available on Amazon: We haven't used it ourselves, but it's highly recommended and we like other Unique RV products.

Citrasolv can be a good option for clearing greasy buildup... so can PineSol (often more readily available and cheaper)... but we'd be cautious (especially with the Citrasolv) that it wasn't too high a concentration so it doesn't damage any seals (like on the blade valves) by being in contact for too long.

James Leonard

Saturday 4th of June 2022

Thanks for this information. In my 25 years of RVing and owning 2 motor homes I had never heard of struvite.

My question is did the cleaning you had done solve the sensor problem? You showed an inside video of the tank before the cleaning can you now show the tank after the cleaning of the same tank?


Sunday 5th of June 2022

Hi James! We're always amazed at how much more there is to learn about ANYTHING we've been doing for a while. It's always good to keep an open mind... you just never know when you're going to learn something new!

We have a post (and/or video) planned that will show that. YES... the cleaning solved the sensor problem, but we also upgraded our tank sensors to the SeeLevel system shortly after that (for greater accuracy on readings, which is very helpful for us with all the boondocking we do). But we DID include the "AFTER" shot in the video we posted about our tank cleaning... you can see it starting at the 12:17 timecode in this video (link should start at that time):


Saturday 4th of June 2022

FWIW, I use a modified GEO method for the black tank (only) at the end of the season before 6-7 months of storage. I do not use Calgon simply because it is sometimes hard to find. I add a container of laundry detergent, a gallon of bleach and fill the black tank, 40 gallons and drive locally for aqbout 5 miles, up and down hills, around curves. Then I dump the tank, fill again with only water and repeat the drive, dumping the tank again at the end. The water is quite clean at the second dump and the tank looks clean via flashlight shining down the toilet. My rig does not have a tank flush system. I do add a bit of liquid black tank deodorant at the start of using an empty black tank. Ten seasons and I've never had any issues with odor, blockage or level sensors.

Note that clean water running through the clear sewer hose adapter does not assure that the tank is clean. It simply indicates no more waste is flowing from the tank. It is possible that stuboorn deposits remain.


Sunday 5th of June 2022

Sounds good! Getting the tank(s) dumped and clean before storing is a great way to help keep them odor free when you use the RV.

Steven Gunden

Saturday 4th of June 2022

Took your advice and had the tanks professionally cleaned by Mike in AZ. Our black tank sensor readings were unreliable at best and NEVER showed 'Empty' despite rigorous flushing efforts. That worked and our sensors are now reading properly. We use the Bio-Geo method on travel days if we've been parked for a week or so. It works for us and helps keep our tank sensors reading true.


Sunday 5th of June 2022

So glad to hear Mike was able to help get your tank sensors reading again, Steven!

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