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Old 12-22-2006, 02:31 PM   #1
1 Rivet Member
1976 26' Argosy 26
Jacksonville , Florida
Join Date: Nov 2006
Posts: 7
Valve Replacement on Holding tanks

Hi everyone, Does any one have experience in replacing the valves on the grey and black holding tanks. I have a 26 foot 1976 Argosy with all the original equipment. The grey and black tanks are in good condition, but the valves leak when they are closed. I believe these valves are called Thetford Valves. My tanks are in the back of the RV as is the Bathroom. I can access the tanks through the back bumper/storage area. There is a panel that separates the the tanks from the storage area in the back bumper. Not sure how to go about replacing the valves, is possible. Any guidance and/or thoughts would be appreciated.



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Old 12-22-2006, 03:00 PM   #2
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sander17's Avatar
1996 28' Excella
Okemos , Michigan
Join Date: Apr 2003
Posts: 305
Images: 42
This past summer I had a similar problem with the black tank leaking thru the valve. I was depending on the sewer cap to retain the nasties. I flushed the dickens out of the tank and took the drain plumbing apart. The whole problem was a hard deposit inside the valve that was preventing the gate from closing all the way. It was indicated by the handle shaft not going in all the way. After cleaning and reassembly, everything is now just fine. I found that there are many different versions of the thetford valve, depending on the year of manufacture and how it is attached to the pipes. All of them seem to have the same model number, so it can be very confusing to order one. It is very simple inside, so if the plastic is not obviously broken, I would recommend getting down and dirty. Just use LOTS OF WATER before opening the plumbing.

Okemos, MI
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Old 12-22-2006, 04:11 PM   #3
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1978 31' Excella 500
Venice , California
Join Date: May 2006
Posts: 1,061
Kits for replacing the seals in the slide valves are available from RV suppliers. The valves are held on with four screws. It's an easy rebuild, if unpleasant. Just did both of mine on the Excella this summer. Hard deposits build up on the surfaces and spoil the seal. A thorouogh cleaning and then lubricating the new seals with silicone grease will make them work like new.
"Not all who are laundering are washed" say Bill & Heidi

'78 Excella 500,"The Silver Pullit". vacuum over hydraulic disc brakes, center bath, rear twin. '67 Travelall 1200 B 4X4 WBCCI 3737
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