Is there a back-flow prevention on the black tank dump valve?

[yourpcgeek49]

We have a 2011 Bighorn and have replaced the toilet with a composting toilet so our black tank sits empty. Taking the suggestion from the Wynn's (http://www.gonewiththewynns.com/product/valterra-t58-twist-on-waste-valve) we installed an external valve with the intention of closing it and opening both the bathroom tank and the empty black tank to allow the levels to equalize. However, nothing flows in the black tank!

Anyone have experience or insight?

 

[danemayer]

If I follow, the composting toilet is emptied without using the black tank. So you have an unused black tank and want to use that as extra capacity to hold gray water. You have the black and gray #1 gate valves open, and the exterior gate valve closed. And as far as you can tell, the extra capacity of the black tank is not being used. I assume that means you have water backing up into the shower when gray #1 fills, but you think the black tank is empty at that point.

Placement of tanks varies by model and floor plan. In our Landmark, the black tank is above the gray #1. So if that's your setup, as you shower, and the gray #1 tank fills completely, the water pressure from gravity has to force water through the 1-1/2" outlet pipe, and then up into the black tank fast enough that there's no backup in the 1-1/2" drain/trap under the shower. It's possible the path of least resistance might be the path into the shower.

 

[jimtoo]

Dan is correct on the black tank location. I have a 3670 and the black tank is mounted above the bathroom/shower tank. I don't think there is anyway the shower will use both tanks without some re-plumbing of the drain lines.

Jim M

 

[JohnDar]

Simply put to use both to drain the shower and lav sink, you would have to replumb so it first flows to the black tank and it, in turn, has an open drain line into Gray #1. When Gray #1 fills, it will back up into the black tank. Problem may arise if the air vent line to the roof from Gray #1 is not capped off. Might have water forced up and onto the roof.


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[yourpcgeek49]

Thanks to all who responded!

Now, I have to decide whether the extra work is worth it!