Freezing P Trap fix

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J Blow

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I have a cabin built on blocks (essentially a mobile home) with a shower/tub that has a p trap right next to an exterior wall in a 'box' below the floor level, obviously. It gets little heat through the tub, although Is insulated well but just the wrong combination of events so when we hit 10-20 below several times a year, it freezes.

Some form of heat tape is really the only logical fix but not sure what I should use on p trap drain pipe. It looks like there's special heat tape for PVC so I'd use that but just want to be sure I'm not doing something else that might cause an issue - like wrapping it to tightly together or something else I maybe haven't considered. Maybe there's a better solution altogether?

Thanks.
 

WorthFlorida

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If this is full time occupancy heat tape may be the only solution. Do get a heat tape that has a built in thermostat so when it warms above freezing it shuts off.

If it's a weekend getaway, pour a few ounces of RV antifreeze down the drain Or daily after each use during freezing temps. It's only about $4 a gallon at Walmart.
 

J Blow

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It's a VRBO. Needs a permanent fix.

I just mostly wanted to be sure I wasn't really not considering something serious and using a heat tape fix or see if there were better solutions.
 

Jeff H Young

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my gun safe has a small heater that keeps it dry insulate around the box its like an inch in diametor and 12 inches or 10 long gets warm.
 

Reach4

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You could insulate your box really well. The XPS foam board is the good stuff.

You can get digital thermometers with a remote sensor. Maybe put one by the trap, and look when you are around. Decide whether to pour some RV antifreeze down the drain after a shower.
 

Jeff H Young

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I dont think a tenant on a short term would bother with pouring anti freeze
 

J Blow

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I'm struggling to find an application I feel good about wrapping the pipe. It's 2" PVC and I'm not sure regular heat take is rated for that in both effectiveness and other specs. Afraid it might get too hot.

Intrigued by the idea of putting a small heater in the but no idea what to consider for that. Ideas?
 

JoeJee

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What I imagine is that you have a tub with a solid floor under it. The drain goes through the floor and you have the p-trap in a box under the floor. See picture for what I am seeing in my head: yes, I paid a lot of money for that rendering so I hope it is helping us…

What about bringing the p-trap inside the thermal envelope? I don’t know the actual design of what you have but if you remove the floor above the p-trap box and then fully air seal/insulate the p-trap box then you should be able to eliminate the need for a heater. If you need a heater then just buy a LED light bulb plugged into a thermally activated outlet (link below). Talk to electrician in your area that can tell you if this needs to be gfi or something.

 

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J Blow

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What I imagine is that you have a tub with a solid floor under it. The drain goes through the floor and you have the p-trap in a box under the floor. See picture for what I am seeing in my head: yes, I paid a lot of money for that rendering so I hope it is helping us…

What about bringing the p-trap inside the thermal envelope? I don’t know the actual design of what you have but if you remove the floor above the p-trap box and then fully air seal/insulate the p-trap box then you should be able to eliminate the need for a heater. If you need a heater then just buy a LED light bulb plugged into a thermally activated outlet (link below). Talk to electrician in your area that can tell you if this needs to be gfi or something.



You have it mostly correct - but your after picture is actually how it already was, which makes it hard to understand why it was freezing. Keep in mind that it was only freezing when it was well below zero (and probably a wind pounding on that side of the house. It also opens up into the house but between walls that wouldn't get a lot of heat. Just above floor level is the water for the tub/shower no more than a couple feet way so surprised that didn't ever freeze - guess being just below floor level was the problem.

I did dismantle the 'box' from underneath to check it out. It was stuffed with insulation and I'm thinking that maybe it was actually covering the top of it versus letting the warmer air from the top seep in. I built the box out and added insulation all the way around it while leaving the top open to house air. I've added a wifi sensor that tracks temp in there and if it still gets below freezing, I'll add an inline air duct to suck warmer air from the kitchen area back to here. We'll see.

Thanks for your consideration on this!
 

Tuttles Revenge

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What I've done for temporary freeze protection is set up a 60watt incandescent light bulb under the object I don't want to freeze mounted with a clip on style lamp. They make outlets that energize at a given programable temperature that would turn the lamp on at that temp and off when the temps rose.

I've seen heat tape set up in this manner too, but a lot of heat tapes just work that way with a thermostat.
 
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