Wednesday, November 30, 2022


RV holding tank dumps — How long can it wait if not full?



gary-736Dear Gary,
I agree with your philosophy of filling the holding tanks almost full prior to dumping. However, my wife and I go to all the home Penn State football games and rarely get half-full over two nights. We stop at a campground on our way home and dump every trip. Do we have to do this every trip or can it sit in the tanks 2-3 weeks and then dump after the next run? How long can you go between dumps? Ray T.

Dear Ray,
As long as you are using a quality, enzyme-based, live bacteria tank additive like Pure Power Blue, I see no problem with leaving the tanks partially filled over the course of a couple weeks. The enzymes will continue to work, further breaking down the solid waste. It’s more of a personal choice rather than a technical mandate. But if you wish to evacuate the tanks sooner, simply fill the tank above the 3/4 mark with fresh water and dump after every trip home. This is probably what I would do, but again, there is no harm (unless odors develop) in having a partially filled holding tank when you start for the next home game.

Some coach owners might argue that they’d rather not travel with that additional weight — especially if they refill the fresh water tank before the start of each trip. As a safety concern, you do not want to have more fresh water on board than you have capacity to capture and retain in the black and gray holding tanks combined. Leaving waste in either tank may push you past your total capacity if you refill the fresh tank before evacuating the waste tanks. It does require some diligence from the user.

 Read more from Gary Bunzer at the See Gary’s videos about RV repair and maintenance.


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Donald N Wright
1 year ago

OK, how long can/ should I keep the potable water in the fresh water tank ? weeks, months ?

5 years ago

Dump the tanks on the way home. If their is some natural disaster and you NEED your RV you will not want the tanks half full.

Chuck Woodbury
5 years ago

Good point, Jim.

JIm Stein
5 years ago

It’s worth noting that the total weight of water and waste probably has a negligible effect, the weight of the individual tank may compromise it’s stability. Many RV’s do not provide adequate support for the weight of a full tank while bouncing down the road. Many are only suspended by the plastic rim. We saw a relatively new 5th wheel on our last trip, sitting on the shoulder with one of the tanks dragging on the ground.

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