Tuesday, January 31, 2023


Ask Dave: How do I keep my RV’s black and gray tanks clean?

Dear Dave, 
Good morning. Other than the Thetford gauge cleaner, what is a good routine to get into to keep black and gray tanks clean and not smelly? Thanks. —Julie

Dear Julie,
In my opinion, it starts with the right enzyme-based treatment product such as the Thetford AquaBio™ products that have no formaldehyde or Bronopol. These products have microorganisms, mostly aerobic bacteria, that start to break down the sewage and digest the organic waste. The process not only breaks down the sewage but toilet paper as well, and eliminates odors. Other products that create an anaerobic process build up ammonia and other odors that create a rotten egg smell and do not break down the components.

Flush out the tank

The next step would be to have a black water tank rinse valve installed if possible. After you dump the tank initially, connect a garden hose to the valve and fill the tank back up. The valve will spray all around the tank and rinse any sludge left on the side or top of the tank and will clean off the level probes. Most manufacturers are installing these as a standard item. If your tank is not accessible from the side you can use a remote flush kit which can be found here.


If you cannot get to the tank, you can flush the tank with a flush wand going through the toilet; however, it is not very convenient. You can find this on Amazon.

I typically like to fill and drain the tank 2-3 times and use a clear elbow at the dump hose connection to see how clean the draining water is. Doing this will take some time, so please use dump station etiquette if someone else is waiting to dump. You may have to wait until you are not hogging up the station.

Since the gray tank is typically cleaner with just shower water with soap and the occasional sink drain, it’s easier to keep clean and less of a hassle. However, I still use the Thetford gray water tank conditioner as it helps with some of the smells you can get from hard water sitting around too long. It has a detergent that helps reduce grease buildup as well as a deodorant. Just dump 1/2 cup of the product down the shower drain after dumping.

 You might also enjoy this from Dave 

Black water tank is clean but there are still smelly odors. Why?

Dear Dave,
After flushing the black water tank, there are still smelly odors like a sewage smell in the bathroom that seems to come from under the sink in the cabinet. I flush the waste tank until the water comes out clean and there is still a strong smell. Is there a one-way valve or something like that that may be stuck open? Thanks. —Luis, 2020 Winnebago Micro Minnie 1706FB

Read Dave’s answer.

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here


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Purple Bob
1 month ago

Another vote for Happy Camper. No fake cover-up perfume smells, actually, no smells at all. That stuff simply works.

1 month ago

Another Thetford commercial.

RV Staff
1 month ago
Reply to  Gary

Hi, Gary. You can ignore the links in the posts, of course. We add them in case someone is interested in reading more about the product or maybe even ordering it. Sometimes when we haven’t linked something we’ve received comments such as, “I wish you would link it so I don’t have to search for it.” So, it’s possibly a tiny bit of income for us, but it’s also included as a convenience for our readers who are interested. Those not interested can just ignore the blue lettering. Have a great day. 😀 –Diane

1 month ago

Happy Camper does it all. I challenge everybody to use it at least once. You’ll notice the results right away.

1 month ago

We’ve used Valterra Odorlos since our first full season, in 2015. It was one of the few unscented products we could find, & works well for us. So many products have scents – if the things works, no asthma-irritating scent should be necessary.
We have a small TT, so only 10 gallons black tank, 30 gallons gray, so don’t know if things differ for larger capacity tanks.
One of the big improvements we had, after battling some odor issues, was to add the Valterra Hydroflush to the dump routine.

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