Freeze-proofing an raised floor trap

[WV-Mike]

Howdy,

I am installing a tub/shower combo in the raised floor dwelling I am building. This waste water will not go to a sewer line but rather dispersed downhill, into the woods, as grey water

One of the vexing issue I have thought about in my brainstorming:
How to keep the raised floor trap on the shower/tub from freezing.
Although there be no sewer gas issue I wish to eliminate outside air from entering the residence, especially in the winter.

The trap will have to be located in the joist cavity which is above ground.
I plan to separately box in this area and add extra insulation.
I also plan to put in a wall vent which will open to an adjacent heated area thinking this might be enough to keep the trap from freezing.
I also thought about adding a check valve to try to limit cold air intrusion into the trap.

I did find this: "Trap Guard waterless trap"
http://www.fmaindustries.com/trapguard.htm
But, it appears not to be on the market yet.

Other than heat tape, has anyone got any there ideas?
-Mike

[Don_P]

Bury the trap in a gravel well with a french drain... a WV septic system (did I say that out loud :nuke:)

[WV-Mike]

Actually, that is something I considered - burying the trap.

But, from previous experience I find French drains do not work with grey water.
Over the years all the fines from clothes washers, meal prep, etc plug the gravel bed and then cause a resurgence to the surface and/or backing up water to the source.

-Mike

[rwanders]

If sewer gas is not involved why are you putting a p-trap in at all?

[WV-Mike]

If sewer gas is not involved why are you putting a p-trap in at all?

My main concern was cold air intrusion in the Winter.
-Mike
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