How to Sanitize RV Holding Tanks – GEO Method for RVs

Looking for a DIY way to get that sewer smell out of your RV? Have you ever heard of the GEO Method? If not, join us as we detail the process.

How Do You Get a Sewer Smell Out of an RV?

Among other things, a common cause for sewer smells in an RV are that they tanks are completely full or there is some nasty buildup causing an empty tank to stink.

It is very common for RV tank sensors to give false readings. More than likely, you have experienced (or know someone) a situation where you have dumped your tanks and your gauges read full, 2/3 full, etc. What?!?!?!

How are you supposed to keep an eye on things? The convenience of being able to take a passing glance at your gauges is the easiest way. Well, not if they aren’t working properly.

What is the GEO Method for RVs?

The GEO Method, which stands for Get Everything Out, is a DIY cleaning method for your gray and black holding tanks that has been around for 40 or more years.

Out of all the benefits, it is most known for really helping to keep your RV tank sensors in tip-top shape by keeping them clean from any buildup.

Sensors are notorious for collecting and getting covered with nasty sludge and everything else in your tanks. This is what causes the bad readings. The GEO method helps with this problem.

It is also a cost-effective way to maintain your tanks and sensors in lieu of buying expensive chemicals.

Our camper is 15 years old and things don’t work as good as they used to. However, I’ve found the GEO Method works really well to keep our sensors in check.

Another benefit is it really helps with keeping smells at a minimum. Some folks have said it makes their tanks smell “good”. I wouldn’t go that far. Plus, I’m not going to be performing any sniff tests for research purposes.

What does it consist of?

Geo Method Ingredients

The ingredients used for this cleaning technique are very basic and minimal.

  • Calgon Water Softener (Some folks prefer powdered, which is cheaper as well). Calgon helps fight limescale, it removes minerals and residue in water and assists in clearing out the nasty scum.
  • Dawn Dish Soap (laundry detergent is an option as well). Dawn is awesome at cutting through grease and slimy residue. It has a nice soapy, cleaning action and really slicks things up to help them slide on out.

There are some that use bleach as a third ingredient. There is some argument around the fact that bleach kills the organism and bacteria needed to run the system.

Others argue that the black tank is a holding tank and not a septic tank, so it doesn’t matter.

I have never utilized bleach and haven’t had a need to.

That’s it…just two ingredients. The simplicity and availability of the ingredients make this method super affordable.

Geo Method Instructions

Before you get started with the geo method, keep a couple things in mind.

Make Sure Your Tanks are Full

By full, I mean mostly full. Try to maintain at least a 2/3 (full is better) capacity before dumping. Even if you are hooked up to sewer services, make sure you keep your valves closed so they tanks can fill properly.

Liquid and pressure are your friends. You need to have enough volume for your tanks to flush properly. When you are hooked up to services and your valves are open, it’s difficult for the solids to vacate the system.

If needed, you can always add some fresh water prior to dumping.

Black then Gray

You want to make sure the nasty stuff is flushed out with the not quite so nasty stuff. So, your toilet water is dumped and then follow up by the shower/sink water. This helps clean out the system of the grossest contents.

Back flush if you need to and you are equipped.

Use the GEO Method | Step-by-Step

You will find varying instructions, ingredients, mixtures, etc., but most are relatively the same. After the tanks have been dumped, I start the process.

Here is what we do:

  1. Make sure you start with some freshwater in your black tank. You can add this via the toilet, but it will take a minute or so of letting the water run. I find it easier to use a mop bucket or something similar.
  2. Fill the toilet with fresh water and add 1 Cup of Calgon Water Softener. Flush this mixture into the tank.
  3. Fill the toilet with fresh water again and add 1/2 Cup of Dawn Dish Soap. Flush this mixture into the tank.
  4. Since the gray tank will likely acquire soap through normal use, I usually just add 1 Cup of Calgon Water Softener and rinse it down the sink.
  5. If you want, you can always add the 1/2 Cup or even a reduced amount of Dawn. It won’t hurt anything.

That is it. Just leave the mixtures in your tanks until they are full and ready to dump again. Once you are full and dump, you can repeat the process.

If you want to put a little motion to work for you, just fill your tanks half full with some freshwater and add the mixtures above prior to travel.

The sloshing of the water and cleaners will help loosen and break up any buildup. You can simply dump your tanks when you arrive at your destination.

Commercial Organic Alternative

If you looking for a safer commercial alternative, try Happy Campers Organic tank treatment. It works really well and offers an organic alternative to those who are looking for that.

The nice thing about Happy Campers is there is not smell whatsoever. With a lot of off the shelf options, you get a definite chemical smell. They are very distinct and hard to miss. You eliminate that chemical odor with Happy Campers, which is important to some.

The substance is biodegradable and septic tank friendly. So, if you are set up and hooked up to a septic tank, you should have no worries. Keep in mind, the GEO Method listed above won’t be an issue for septics tanks either.

Happy Camper also claims to break down regular household tissue, eliminating the need to buy expensive RV specific tissue products.


I’m not sure who “invented” it, but after using it for a while I came across a post by Charles Bruni describing it. He states in one section that he came up with it. He may in fact be the originator, and if so, well done.

We have found this method and our version to work really well for us. Keep in mind, there are other techniques, methods, and commercial options available for you to try. It doesn’t hurt to shop around to find what works for you.

If your camper has been sitting like ours was, you may have to run 2-3 cycles of the GEO Method through the system before it cleans things out. Let each cycle sit for a while before dumping and repeating. If you have a newer rig, it may only take once.

Happy camping!



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