black water valve leaking

[TOak]

I'm trying to help out a friend with SOB with "her" black water leaking problem. The valve leaks by. I have tryed back flushing, filling the tank and dumping with full pressure but nothing seems to stop it from leaking. Does anyone know if there is some kind of brush that is 3 1/2" wide to push up the pipe to clean the rubber seat? You can't see the valve and the cable has to much flex to push the valve tight. I know it makes a 90deg turn up into the tank but like I said, you can't see the valve. Any help will be greatly accepted.

[CORattler]

If the things that you tried already don't work, I'd suggest replacing the leaky valve. This was the only way I got my previous S.O.B. to work correctly. (Sorry for the bad news!)

[Carl n Susan]

Replacing the defective valve is the proper fix, but in the mean time add an external gate valve. Camping World (and many others) have these gate valves which hook onto the end of your sewer outlet pipe. The sewer hose then hooks onto the gate valve. Here is a link to the Camping World product.
http://www.campingworld.com/shopping/item/twist-on-valve/27868

Many of us use one of these external gate valves to protect against any surprises when opening the end cap (it happens more often than you think) and to equalize the two gray tanks when boon-docking. A leaky black (or gray) tank valve is just another reason to use one of these.

[camper4]

I also have a leaky black water valve. I have to be careful when I remove the discharge end cap... sometimes it is a small amount and other times it is larger.
I like the idea of adding a valve to the discharge pipe. I can get at that to clean it. I don't camp in freezing weather so that sounds like an easier fix than replacing the valve close to the tank.
Thanks