how to clean your black water tank

Have not heard very many talk about this one......I have done it for several years now and it works for me...
Just before you go to the RV 10 lbs of cubed comes in a big plastic bag. break it up and dump it into the toilet with the flush valve open......then drive to the dump.....might want to take a little side trip around the block...I usually try to make several turns. The ice cubes (having sharp edges) will scrape the "crap" off of the inside of the tank and it will all go down the drain as slick as 1.2.3...... What do you think of that.
Re: how to clean your black water tank

Wait til you hear how we make the inside of the tank slicky and really get rid of the stuff. You want never ever need the ice cubes again.

C Nash

Senior Member
Re: how to clean your black water tank

Yep, the ice will work ironart. Did that on a old rv we had that had been toilet abused :laugh:

C Nash

Senior Member
Re: how to clean your black water tank

woops, had to read your post several times Hollis. Thought you said ice cream :laugh: :laugh: :laugh:


Senior Member
Re: how to clean your black water tank

The ice cube trick is one that many use and feel works. I don't bother with it since we are fulltime and we put more "stuff" back into the tank shortly after we dump each time anyway.
Re: how to clean your black water tank

Hi Kirk,
Would love to be full timing but the wife won't give up her goats yet...I working on a little "cage trailer" to put them in (3 dwarfs and 1 neubian)
We did spend 13 years living on our boat and going everywhere......Wife loves to fish and we spent a lot of time out looking for the "Big Ones"
Traveled mostly along the west coast Frisco and Sacramento river down to Mexico. Loved every minute.
RE: how to clean your black water tank

Thanks for the tip, I had never though of that before. It worked well for me when I tried it today. I also tried the cailgon stuff to and it helped as well.

C Nash

Senior Member
Re: how to clean your black water tank

Not hard to tell when a dealer is crooked. Guess we all could go to his website and post all kind of :question: to his expert and get free quoats on ALL his rvs :laugh:
Re: how to clean your black water tank

We bought a 97 HR DP several yrs ago. We have tried everything, but the ice, and can't seem to get rid of the odor in the holding tanks. We have a backwash system and use it with each dump. And make sure it's always washed out when sitting awhile. Any suggestions......I once read on a forum about some simple remedy to put down the commode, but can't remember what it was. Didn't need it with the other mtrhome. Also.......we installed a riser as we're disabled. It keeps leaking onto the bath floor. It's been retightened several time but still the floor smells like 'pee'. We installed one on another mtrhome and didn't have any trouble. HELP!! ON BOTH PROBLEMS. THANKS

DL Rupper

Senior Member
Re: how to clean your black water tank

See if you can get someone to check the holding tank vents on the roof. If the RV holding tanks are properly vented they shouldn't smell. Try dumping some bleach into the drain traps and letting it sit for awhile and then rinse it out into the holding tanks.
RE: how to clean your black water tank

goldwing1987, if you have an ammonia smell on the floor check your toilet. A cracked base or bad seal will result in an ammonia smell on the floor. If your toilet tips or is not flush the base can crack & you may need new parts or a new toilet.
As DL Rupper suggested check the roof vents. If you have backflushed & chlorinated without results try snaking. Snake all your gray water & black water sources including tanks as well as p traps. If you are getting stuff out with snaking, you will probably need a strong digester to clean out remaining material. You can buy products to use in both gray water & black water tanks. The home remedies will not work for serious problems. The ice cube trick is not for full timers. Make sure you are keeping your tanks closed, & liquid in it. Once your p traps are clean make sure they have water in them. Other things that can cause problems are incorrect pipe pitch, incomplete dump valve opening. or a main drain problem. Remember your chemical used should have a digester in it. If you are not using a chemical with a digester or not using a chemical that may be the source of buildup.
There are venturi products available for vents, but I personally do not believe they should be used unless the system itself is clean. In small print they usually say p trap siphon is possible, so if you do decide to use a product such as this remember to routinely check your p traps.
Re: how to clean your black water tank

elkhartjim - 8/10/2008 6:42 PM Wait til you hear how we make the inside of the tank slicky and really get rid of the stuff. You want never ever need the ice cubes again.

I'm kinda waiting to hear how you do it - or did I miss something?
Re: how to clean your black water tank

Glenn NK - 9/10/2008 2:32 PM

elkhartjim - 8/10/2008 6:42 PM Wait til you hear how we make the inside of the tank slicky and really get rid of the stuff. You want never ever need the ice cubes again.

I'm kinda waiting to hear how you do it - or did I miss something?

This is probably what is being referred to. I also use this method and it works.

The Original Geo Method Homepage and Blog

Black and Gray Water Holding Tank Maintenance

The Geo Method

By Charles Bruni
Renton, Washington

Everyone who owns an RV should be concerned with maintaining its wastewater tanks. Problems with wastewater tanks can and should be avoided. Wastewater tank repair is expensive. Due to health concerns, many service facilities will not work on wastewater tanks and lines until the tanks have been completely emptied and sanitized. This may be quite difficult when the tank(s) is in need of repair. So, common sense dictates that the tanks should be kept relatively clean at all times. Additionally, improper use of the wastewater tanks can lead to a build up of solid wastes, which in itself may cause the system to fail.

I've discovered very simple, effective, and inexpensive methods of maintaining my wastewater tanks in a relatively clean condition at all times. I developed these methods myself through my understanding of chemistry, physics, and biology with a smidgen of common sense thrown in for good measure. I also read my RV owner's manual. Although we are not full time RVers we use our fifth wheel camper at least one weekend a month. We never use public bathing and toilet facilities. In other words, our wastewater tanks are fairly heavily used. Since I've met a number of RVers who don't seem to know how to maintain their wastewater tanks I thought many RVers would find my tips useful. If you have not been maintaining your tanks I believe you will be pleasantly surprised the first time you employ these tips. I do these things and they work.

RVs are equipped with waste water HOLDING tanks; NOT septic tanks. Those holding tanks are nothing more than chamber pots. Chamber pots should be cleaned and sanitized after their contents are disposed of. The Geo Method is based on this fact.


When you are camping and your RV is connected to a sewer/septic intake, leave the drain valves closed until the tank is full and ready to dump. Dumping a full tank provides a sufficient quantity of water to flush solids from the tank. Leaving the drain valves open allows the water to drain off without flushing out solid waste. That solid waste will collect in the tank(s) and cause problems over time. If your tanks are not full when you are ready to dump them, fill them with fresh water first, and then dump them.


In other words, dump the black (commode) water tank first, then dump the galley tank, then dump the bathroom tank. This way you will be flushing out the dirtiest water with progressively cleaner water.


This stuff is amazing and it works. Buy a couple of boxes of powdered water softener at the grocery store. You'll find it located with or near the laundry detergent products. I prefer Calgon Water Softener because it dissolves quickly in water. Cheaper water softeners work just as well but dissolve more slowly. Dissolve two (2) cups of the water softener in a gallon of hot water. Then, pour the solution down the drain into the empty tank. Use two cups of softener for each wastewater tank in your RV. The tank's drain valve should be closed otherwise the softened water will just drain out. Then use the tank(s) normally until it is full and drain it normally. Add a cup of laundry detergent to the black (commode) water tank at the same time you add water softener. This will help clean the tank. The gray water tanks should already contain soap through normal use.

The water softener makes the solid waste let go from the sides of the tanks. If you've ever taken a shower in softened water you know that after rinsing the soap from your body your skin will feel slick. That's because all the soap rinses away with soft water. Softened water also prevents soap scum from sticking in the tub. Get the connection? With softened water gunk washes away instead of sticking. The same thing applies to your RV's wastewater tanks.

I use a clear plastic elbow connector to attach my sewer drain line to the wastewater outlet on my RV. It allows me to see how well things are progressing during a wastewater dump. Before I began using water softener regularly the black water tank's water was brown, the galley tank's water was brownish, and the bathroom tank's water was white. The first time I added water softener to the tanks the water coming from the black water tank was actually black (not brown) and the kitchen tank's water was also black (not brownish). The bathroom tank's water remained white. That told me that the water softener had actually done what I had intended for it to do and made solid waste, which had been stuck to the interior of the tanks, let go and drain away. I added water softener (and laundry detergent to the black tank) to all the wastewater tanks for the next few dumps to be certain all the solid waste possible had been cleaned away. The wastewater only appeared black on the initial treatment. I now add water softener and detergent to each tank once after every few dumps to maintain the system.

Too little water softener may not be of sufficient concentration to work effectively. Too much water softener will NOT hurt the tanks. So, if the amount you used didn't quite do the job, then use more the next time. Don't forget the laundry detergent.

Occasionally, I pour a half gallon of liquid bleach into each tank to deodorize, sanitize and disinfect them. I add the bleach when the tank is about half full, and then continue to use the tank normally until it is full and ready to dump. I no longer use the blue toilet chemical because it isn't necessary. I have no odors coming from my black water tank. The chlorine bleach kills the bacteria, which is primarily responsible for waste water tank odor. Generic brand liquid bleach is cheap and very effective.


Most fresh water contains sediment. Sediment will accumulate in your wastewater tanks and your fresh water lines. It also tends to discolor your sinks, tub/shower, and commode. I use the disposable type and have found that they eventually fill up and begin restricting the fresh water flow resulting in low pressure. That's how I know it's time to get a new filter. It works, it's cheap, it avoids problems, do it. When I fill my fresh water tank I attach the filter to the end of the hose and fill the tank with filtered water.


WATER, WATER, WATER - and more water! The Geo Method assumes you are hooked up to a plentiful clean water supply, and that you have access to a sewer. The water softener will make the gunk let go. That's only half the battle. After the gunk lets go it must then be flushed through the relatively small drain opening in the bottom of the tank. That takes water. Lots of water.

Will The Geo Method work even if most of the time I'm NOT hooked up to water and sewer? YES! Just use common sense. If you dry camp ninety percent of the time just keep water softener and detergent in your tanks (especially the black tank) while you're dry camping. This will keep gunk from sticking to the tanks. When you are hooked up to sewer and water take the opportunity to fill the tanks with fresh water and flush the tanks. Keep flushing them until the water runs clear. I know it works because I've done it.

Never put regular toilet tissue in your RV's black tank. Only use toilet tissue which is approved for RV and/or septic tank use. Regular toilet tissue may eventually dissolve, but not before causing a clog in your black tank.

I believe occasionally traveling with partially filled wastewater tanks that contain softened water promotes cleaning by agitating the water. The same goes for chlorine bleach.

I believe this process works faster and more efficiently during warm weather. However, I know it works well even during cool/cold weather.

I believe the process works best the longer the water softener remains in the tanks. So, I don't add water softener during periods of heavy wastewater generation. I wait until I know we won't be generating wastewater quickly so that the softened water remains in the tanks for several days before dumping.

If you have an older RV you may have to use water softener and detergent several times initially to completely clean the tanks of residue.

I add a small amount of chlorine bleach to the fresh water tank twice a year to disinfect and sanitize the fresh water tank and fresh water lines. A weak chlorine bleach solution will not hurt you. However, it certainly makes the water taste bad. When we have chlorine in the fresh water system we use bottled water for drinking and cooking until the chlorine is gone. YES, we drink the filtered water that we have in the fresh water tank. NO, it has never tasted funny or caused any problems.

No, I do NOT do the ice cube thing. The Geo Method works just fine without ice cubes.

My tanks are plastic and my pipes are PVC.

Don't be afraid to use your tanks. Just use common sense about their care and maintenance.

These tips are inexpensive to do. Some of them don't cost anything. You have nothing to lose in trying them and I encourage you to do so. I actually feel a certain amount of pride in the condition and cleanliness of both my waste and fresh water systems. Naturally, these tips make dumping a much more pleasant and sanitary procedure.

If you have odors in any of your water systems these procedures should eliminate them. Odors indicate a sanitary problem and degrade the enjoyment you derive from your RV.

When my RV is parked and not in use I place stoppers in the sink and tub drains. This forces the wastewater tanks to vent through the vent pipes to the outside instead of through the drains into the RV. Water evaporates. Once the drain traps dry out during periods of non-use, nothing is there to prevent gasses (odor) from venting into the camper. Use stoppers when your RV is stored.

Copyright(c)Charles Bruni

Please consider printing this information and posting it on bulletin boards in RV parks and campgrounds you visit. Fellow RVers will benefit from your consideration.