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Old 08-01-2010, 11:03 PM   #1
2 Rivet Member
1960 26' Overlander
Everett , Washington
Join Date: Sep 2007
Posts: 24
Strange Blackwater Tank/Dump Valve

I have a 1960 Overlander with what I thought was the original blackwater tank. It's above the floor on the curb side in the rear bath and appears to be 12 gals or so. I'm now wondering since I can find no information here that is similar to what I have. I need to repair/replace my dump valve which is prompting this thread.

My tank is fiberglass, with a 2" exit pipe glassed into the bottom of the tank. The exit pipe has two threaded ports below the tank for attaching the grey water drains for the shower and kitchen/bath sinks. There is no evidence of hardware or flanges of any type on the bottom of the tank. At the top of the exit pipe, inside the tank, was a concave cap with a rubber seal similar to a flapper valve on a home toilet. The cap had a threaded brass rod running upward from the center, through an approximate 4" round threaded access plate on top of the tank. The handle of the brass rod has tabs that mate with tabs on the top of the access plate. The cam action of these tabs when mated exerts downward pressure on the flapper valve and seals the tank. To dump (from the bathroom inside the trailer), you twist the handle of the brass rod, unmating (is that a word?) the tabs, and pull up. This raises what I am calling the flapper valve from the top of the dump tube and the tank empties.

Is anyone familiar with this type of black tank plumbing and dump valve arrangement? I don't have clearance under the belly pan to add a thetford or valterra gate valve and still tie my greywater lines in below such a valve. I was hoping to find a replacement dump valve or a source for parts. I suppose I could also add a gate valve to the dump tube and plumb a separate dump tube for greywater but that raises other issues. Any ideas short of starting over with a new tank? Thanks in advance.

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Old 08-02-2010, 12:27 AM   #2
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1959 24' Tradewind
The Grass Capital of the World , Oregon
Join Date: Apr 2010
Posts: 174
Images: 6
pictures please

Sounds like you described the same plumbing rigged in the "upper deck" of a typical house terlet. I'd be surprised if it was factory spec. Mine had some pretty awful things going on with the black water, but nothing that Rube-Goldberg'ed.

Post some photos if you get a chance. You may have to rip her a new one to properly drain the grey.
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