More of a warning then a tip!

Making a couple of plumbing repairs to my 19 year old Class A. One of them was my black water knife valve was leaking, not serious, but when you removed the drain cap a bunch of stinky brown water would come out and run all over everything. So I went to the RV parts store and got a replacement seal kit. So this morning I take apart the valve.

Now this is a system where the gray water tank and the black water tank share a common discharge, using a molded plastic assembly that has a knife valve at each end. I removed all the screws for the black water valve, but couldn't get it out of the piping. It seems that the seals extend into the ends of the adjacent pipes. So, I took the screws out of the gray water valve and gave a little tug, and the whole assembly popped out. I cleaned everything and put the new seals into the black water valve and start to reassemble. Now hears the rub. :( On my RV, everything is glued solid, there is no give or take in the assembly and it's impossible to put it back together again without damaging the seals. The bitch of it is there is no space to cut the pipe and put in a union or some other device to allow me to reassemble the valves. My only hope is to find a piece of large diameter rubber or vinyl hose that I can clamp onto the ends of the fittings, thus allowing me to cut out a section of the ABS pipes to reassemble the valves. If this is unsuccessful, then I'm looking at dropping out the both tanks in order to replace these stupid seals. Who would design some thing this way? :mad:


Senior Member
Hi, Scott
As The Clodhopper said .. they are just plumbing parts...
You should be able to go to Lows or Home Depot. and find something that will work..
Sometimes you can take the parts from the new valve and use them in the Old valve body, then reuse the old part
Good luck...... M i c k e y MOUSE.... the old standby buddy
Pancanbob and TexasClodhopper,
Thanks for the advice, that is what to occurred to me to do, just as I was reaching my frustration peak. I cut out the piece that would go from the pvc pipe to the 1.5" gray water knife valve and took it to Home Depot today. There they had a 2" to 2" vibration reducer, I believe that's what it was called, anyway, some heavy walled rubber tubing with clamps on each end. I had to whittle it down a bit, but it's all back together now. Tomorrow I'll fill my tanks and see if I have any leaks. Thanks for the input!:triumphant:
Grandview Trailer Sa;74947 said:
Honestly, I have never seen a system so tight you could not replace the gate valves and seals without damage...sorry but everything has some give.
Well, in my Georgie Boy Curse Master there's only about 16" between the tanks, so it's really tight. Maybe, at some time with the previous owner, they made some repairs, because there was an adapter and a coupling where there should have been straight pipe. But for more than two hours, I tried lubricant, clamps, levers, everything I could to get that last 1.5" knife valve into the assembly, and just couldn't do it. I even managed to damage the end of the fitting that the knife valve attaches to in the process. A colorful metaphor would be a Great Dane making love to a Chihuahua, it just wouldn't fit.