The Thetford Dump Valve

This thread addressed a problem getting valves out of a mid-bath Airstream, so clearances and access to both sides of the valve were of interest:

The valve bodies consist of two flat plates held together by 9 screws. From the look of your drawing, if you take out the screws on both valves, it seems that the “Y” fitting and the two halves of the valves that are attached to it should slip out. The problems I can imagine are:

  1. The “Y” fitting feeds a pipe that goes through a hole in the frame and so it can’t slip out sideways. Do you have an access panel that allows it to go downwards?
  2. You can’t get your hands into the space to use a screwdriver on some of the valve screws.
  3. The half of the valve attached to the tank is attached permanently (that’s how it is in two of my Airstreams). If that half has the seal/gasket material, then you won’t be able to fix the valve unless the seal is replaceable. Some models of the Thetford valve have a replaceable seal, some don’t. I think it’s the stainless version that has the permanent seal.

If you have an RV dealer near you, call and see if they stock the Thetford parts. If so, go there an look at them before you decide what to do. … let me go look in the shop…

Aha, I have an example. This model (8706) is attached to the tank with 4 large stainless screws and is sealed by an O-ring. The valve gasket/seal is removable. Sometimes you can find this seal and the large body seal for the valve (like a head gasket, all the way around where the screws are) as an individual item.

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