Ask Dave: I want to clean my black tank valve but I can’t find it

Dear Dave,
I am living in my motorhome because Hurricane Ian flooded my house. I can’t find the black water tank valve. However, I know where the handle is to open and close the valve, but I want to find the valve itself so I can either clean it or replace it. I have looked all over the place for it. I can’t find it in the service center like the other valves. On another topic, I wonder if I can refill the propane tank without taking it to a dealer. Thanks for your help. —Thomas, 2017 Winnebago Vista 29E

Dear Thomas,
First, sorry to hear about the flooding. I hope everything comes out as best as can be.

Where is the black tank valve?

Your Vista is a Class A and the black tank valve is located in the service compartment on the driver’s side. The model I looked at on RV Trader had two gray tank valves and the black water handle on the right side. If you can’t find it, take a picture and send it to me.

The lower right hand is the handle and the valve is actually remote back in the middle of the coach. Winnebago has a great 3D image and it shows the valve on the tank.

Here you can see the handle on the right. You can also see the cable going to the remote valve, which is yellow. The black tank is located directly below the toilet and has a stair-step design. What I cannot see is how to get access to it. It would be under the floor in a compartment but not always very accessible.

Cleaning the black tank

If you just want to clean it, I would suggest using Thetford Tank Blaster. This will clean everything in the tank as well as the tank side of the valve. Then condition the seal with Thetford Drain Valve Lubricant.

In some cases, you could snake a low-pressure hose through the pipe in the service compartment and clean the outside portion of the valve. However, it looks like there are too many 90-degree bends to get anything close to the black water valve.

LP tank

As for the LP tank, you can install an Extend-A-Stay valve and add another DOT cylinder such as a 40-lb. version that you could disconnect and take to a propane distributor with another vehicle. That way you don’t have to unhook everything on your motorhome and take it to a dealer.

This is one we installed on a 2015 Thor, with the connection for a portable grill. You would need the POL (originally for Prest-O-Lite, BTW) valve connection to connect to a DOT cylinder.

 You might also enjoy this from Dave 

My RV’s black water flush valve doesn’t work! Why not?

Dear Dave,
My RV’s black water clean-out valve has quit allowing water to go into the tank. Why doesn’t it work? —Ronald, 2002 Newmar Mountain Aire

Read Dave’s answer. 

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

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