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Old 05-13-2013, 09:14 PM   #1
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1969 27' Overlander
Boise , Idaho
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Repairing Thetford Valve

The Thetford waste drain valve from 1969 leaks when closed. What a surprise after 40+ years.

I removed the valve, and bought a seal replacement kit. Here's the kit I bought, which I THINK is the right kit, but I haven't opened it yet, in case it needs to be returned.

Here's the critical piece of the valve that needs to be disassembled so I can get to the seal inside, which is failing to fully seal.

The problem is that at the four points where screws attach this valve to the rest of the valve body, there is a brass sleeve through the valve body, which is flared at both sides so that even with the screws removed, it holds the valve body together. Maybe these pics will show it better:

So how do I remove the stainless steel backing plate from the plastic valve body so that I can get to the seal inside? Any ideas?

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Old 05-13-2013, 11:13 PM   #2
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1999 34' Excella
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According to words on package there is another part number for the stainless.

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Old 05-13-2013, 11:49 PM   #3
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1969 27' Overlander
1976 Argosy 28
Lodi , California
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I need to replace this also so any helpful hints would be great! Thinking about switching to valterra since it seems to be more Universal.
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Old 05-14-2013, 05:39 AM   #4
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1993 21' Sovereign
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My suggestion would be to simply purchase a replacement valve. Bolt it on and you're done with it.
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Old 05-14-2013, 05:49 AM   #5
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You do not have the correct repair kit. I have rebuilt these valves in the past with the correct stainless steel cover valve repair kit. It was on a Thetford Slode-O-Matic toilet restoration. You can make it work with the all plastic valve repair kit, but it isn't worth the time on a dump valve, when you can simply replace the valve. New, all plastic, Thetford valves are available. You may want to consider converting to Valterra.

Work is never done, so take time to play!
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Old 05-22-2013, 04:12 PM   #6
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1968 30' Sovereign
Rowlett , Texas
Join Date: Nov 2012
Posts: 23
i am going thru the same thing. that is not the right package. i drilled out the 4 gromets so i could get it apart, only to figure out the kit is wrong. now that i can read i will get the right one
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Old 05-22-2013, 06:39 PM   #7
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1972 Argosy 20
Snoqualmie , Washington
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Posts: 379
Yep, wrong kit. I went through something similar on my 72 Argosy. You can switch to Valterra IF the valve seat that is attached to your black water tank is removable, and if so I think that would be a good idea as Thetford is phasing out the valves. Here's a thread on my travails

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