Is It Safe To Run A Tank Rinser With The Black Valve Closed?

Many RVs are now equipped with a blackwater holding tank rinsing port as standard equipment. There are also aftermarket rinsers that can be installed on RVs which did not come with them from the factory. In almost every RV they are installed in, there are caution stickers warning to make sure that the black tank valve is in the open position. But is it safe to operate the rinser with black tank valve closed?

Tank Rinser Problems

There are certainly many opinions all over the internet when it comes to these instructions. So let’s look at the basics: Tank rinsers work by connecting a garden hose to the RV fitting labeled “Black Tank Flush”.

Then, with the pressure from the water source, they either spray water in a pattern or spin the rinse head to spread water to different areas of the tank. The problem with tank rinsers is that they are limited by the water pressure from the source. If the pressure is too low the water will just trickle into the tank.

If the water pressure is too high, the water will often bypass the majority of the holes in the rinser or spinning head and flow in an odd direction. This will keep the spray pattern of water from hitting the necessary areas of the holding tank.

Having tested tank rinsers before installing them on a holding tank, I can attest that the amount of water they spray is mediocre at best. Even with the factory recommended water pressure, the rinsers spray pattern extended only five feet. Granted, a 40 gallon tank is not a big surface area overall, but the results were still disappointing. 

So why would all of the factory recommendations state that you should have the valve open while rinsing? The reason is two-fold: first, holding tanks fill up fairly quickly, and if there is no one monitoring the water level in the tank it can overfill, making a mess inside the RV. Secondly, the tank can break free from the supports that hold it to the RV if it is overfilled. To prevent these two events from happening the factory recommends keeping the valve in the open position while using the rinser. 

Benefits of Leaving The Black Tank Valve Closed

Keeping the black valve closed while using a rinser does have some benefits. It will allow the water to fill up to levels that the spray pattern does not necessarily hit. Also, there will be a more forceful flow of water when the valve is opened again, washing out more waste and build-up than if the valve was left open. 

The Takeaway

Proceed with caution. Although keeping the black tank valve closed while running the tank rinser can clean better than just leaving it open, there are risks that come with it as mentioned above. We recommend having someone inside the RV monitoring the water level in the tank from a toilet.

If that is not possible, you should  monitor the tank level sensor at the control panel. Another option is to allow the tank to fill for a designated amount of time before opening the valve, then closing it again to refill the tank with the rinser. Setting a timer on a phone is a good way to keep track of the time while filling the tank. If you are uncomfortable with any of this due to the risks, simply use the tank rinser with the valve in the open position. 

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