Thursday, June 1, 2023


Ask Dave: How do I eliminate “poop pyramids” in the black tank?

Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. Today he discusses RV’s black tanks.

Dear Dave,
We are going to be snowbirds in Florida for the next three months and I am concerned about getting a poop pyramid in the black tank. I usually take my walk to the bathhouse, but this fancy park doesn’t have them. Are there any preventive measures I can take? Thank you. —Joe

Dear Joe,
Pyramids are a wonder of the world in Egypt, but not so much in the RV world. The best way to eliminate them is to keep your valves shut and only dump when the tank gets 1/2 to 2/3 full, and use the proper chemicals. I start with a bottle of valve lubrication from Thetford and then the Thetford enzyme-based product.

This product has what my local sanitary district technician calls the “good bugs” that actually decompose the sewage to break it down and reduce odors. I did a feature video on the sanitary process and although it was pretty gross, the chemistry was interesting. I would also suggest running a gallon or two of water down the toilet occasionally just to help suspend the solids and allow the bugs to work.

Toilet paper

Also, use RV-approved toilet paper as it will decompose quickly. We did a test on several brands and Thetford was the quickest. Even residential toilet paper that was designated for septic tanks took a very long time to decompose.

One other item I would recommend is a black tank flush valve on the side of the tank. When you dump the first round, hook up a dedicated hose and this will blast around the inside and clean the walls and sensors.

I also recommend a clear or at least a semi-transparent hose connection either at the valve or at the end of the hose to see the condition of the dump liquid. Dump the black water tank once, run the black tank flush valve until the tank is 2/3 full again, dump a second time, and fill back up to 2/3 and dump a third time. You will be surprised at the remaining sewage the second time. Hopefully, the third dump is clear. Then dump the gray water tank. I know it takes longer, but it will help in getting most of the solids out and keep the pyramids where they belong, over in the Middle East next to the Sphynx!

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Dave Solberg
Dave Solberg
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. He has been in the RV Industry since 1983 and conducts over 15 seminars at RV shows throughout the country.


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Michael Galvin, PhD
1 year ago

Three Thetford products mentioned….
Reviews I have seen put Thetford toilet paper in the bottom half of preference.

1 year ago

Keep it clean by natures way – We use RidEx in both tanks. No problems in over 20 years We also buy TP at Dollar General or the Dollar Stores – dissolves in about 10-15 seconds. (Put a few sheets in your sink and try to pick it up!). I also use TST liquid with an orange scent for pleasant inside odor. Contents are 99.5% (est.!) liquid when dumping – no paper, no solids!

Glenda Alexander
1 year ago

I would NOT recommend the toss-ins. Several years ago when I had to have my black tank flushed, the man said that those pods did not disintegrate. From then on, I opened the packets and poured the contents into the tank. After I had used them all, I started using only liquid.

martin a
1 year ago

There is a lot of discussion on other forums, a great many say that plain water along with the organic matter that you personally add is all you need. Use an appropriate TP and plenty of water has worked well based on my experience and many I have read.

Tony R
1 year ago

Many rivers know this already but for those that don’t know, just empty your black water tank every two or three days, close the black water tank valve and then open the gray water valve. This will keep your stinky drain hose clean by the shower soapy water. Then close your gray water valve again. Then flush your toilet a few times to have some water in the bottom of the black water tank to prevent pyramids, add your favorite chemicals and you are all set ..

1 year ago

I have found that when you are on hook ups use lots of water. We add water after and before flushing. The extra water washes away the pyramid before as it starts to form. You have to dump black tank a little more often but worth it. Easier to prevent than to deal with one.

1 year ago

I have had no good luck with using toss in bags in the black tank. My findings are the bags themselves don’t disintegrate but the inside product does. This leaves the empty bag to clog up my macerator. It is no fun taking a long screw driver and poking around inside there to remove the bag that has clogged my macerator. So far these bags are the only thing that has caused a clog.

Jeff Grossman
1 year ago
Reply to  Eddie

We’ve been using Porta Pak pods for several years and have never had a problem. I drop them into the bowl and fill the bowl with water. I flush after they have dissolved fully. Very happy with them.

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