03/29/2026
Q. Does my RV’s onboard tank flush do anything?
A. In almost every RV, the black tank has an internal spray nozzle that spurts out water into the tank. Water is supplied to this spray or flush system via a garden hose that attaches to the RV park’s water supply at your site and then to a garden hose fitting on your RV. Some RVs (like Country Coaches) have a similar system in the gray tank (this is not common).
Some models have a rotating nozzle, though most are a simple spray head, located at either the back or top of the tank. Most manufacturers (and dealers) will say that this flush system is all that is needed to keep your tank clean. We tend to disagree, though the system does have some benefits.
For one thing, it’s better than nothing. The spray nozzle tends to spurt water in a set pattern at about 100 to 150 PSI (depends on the park water pressure, size of the nozzle hole, and whether the hole is stopped up (more on that later)).
Does it do a complete job of keeping your holding tank clean? No. But it can help to “move things along” when you use it during normal emptying of the tank (something we recommend).
If over time, you don’t think the spray system is working anymore or the amount of spray is lessening, it probably has some corrosion at the spray head. Take some CLR, our about a cup down the empty garden hose, connect it to your RV’s flush system input, and quickly turn on and off the water, driving the CLR to the nozzle head (just a few seconds is all that is needed). Let this “sit” in the system for a half hour them flush the system out (and empty your tank — that CLR is super bad for soft rubber seals).
