I have a two story home with a basement and septic system. The house is 10 years old. There are two bathroom on the second floor. They are located on exterior walls. The drains in the bath and shower freeze up when it is subzero outside. There is no smell and the toleits and sinks in these two bathrooms work fine. We had this problem late last winter and were told to use rv antifreeze. I really need some professional help but don't know where start. Any advice would be helpful. I need to find out the cause before I can even think about fixing it. So frustrated with my problem.

there is insulation missing somewhere. the real fix is to find out where and get it insulated properly.

Not a plumber, but it seems that there's a poorly insulated cavity or void space next to an exterior wall under the tub/shower is allowing the p-trap to freeze. If RV anti-freeze works, it would support the theory. What is directly underneath these tub/showers? If it's just sheet rock, a square piece could be cut out and High R value insualtion could be packed in. My 2 cents.

For a tub or shower trap to freeze, you have a wind tunnel below the floor of those fixtures. Hard to believe on a house only 10 YO.

Pardon Me. Gimme a break. SOMETHING is causing the tub/shower drains to freeze. That's why I suggested that if possible, a square inspection hole could be cut to examine the void under the tub/shower area to see what is what. How is the house constructed? What is the composition of the exterior walls? Has the house suffered any storm damage? If there a possibly a dryer duct vent to the outside nearby has come loose? Are there any defects in the air handling ductwork?

What do YOU think the problem might be?



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At 10 years old it probably was insulation that wasn't installed, and possibly other factors. What it amounts to is that the cavity isn't maintaining the internal temperature of the house, which would only happen on a second floor if it was built out over an overhang, or isn't insulated. Or leprechauns are pouring liquid nitrogen in the drains. I think gremlins with freeze rays is a little far fetched however.

The area where the pipes are is not receiving enough heat. When you have pipes, heated air needs to get to the pipe to prevent freezing especially in WI an MN where you have severe winters. Sometimes putting a grill or louver over a hole cut in the drywall near the pipe is enough to allow warm air access to the pipe that freezes. When you cut the hole, inspect the space surrounding the pipe. Is there no insulation between the pipe and the exterior wall? Is there cold air coming into the space? If so correct these problems.

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Once you have warm air access to this space , then you must protect the space around the pipes at risk with insulation and seal it against air leaks to the outside. The insulation may be placed on the wall (Cold) side not over the pipe which will allow the heated air to get to the pipe. Caulk any areas of air leaks or use expanding foam to block the air leak. Please repair the vapor barrier if you damaged it making the hole. This can be replaced with either new plastic (4 mil is standard) or closed cell foam.

If the p trap is freezing the supply side may be at risk also. Check out these pipes to the valve to ensure they are protected at the same time.



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Do NOT install a grill as you will compromise the vapor barrier and allow humid air to condense INSIDE your wall.

You will need to add insulation and or a vapor barrier as necessary to correct the IMPROPER condition allowing your drains to freeze.

Temp. for the winter - add a little RV antifreeze to the traps.

When spring arrives - open up the wall as necessary to PERMANENTLY and PROPERLY correct the defect(s).

You may need an architect / engineer to determine problem if you are 'unknowledgeable'.

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

The CAUSE is cold air around the traps and insulation does NOT prevent freezing it only slows the process down if there is no warm air available to help prevent freezing. WE cannot tell you HOW to prevent them from freezing because we do not know how the house is constructed. Since it is on the second floor, there may be a means to allow warm air from downstairs to flow around the traps. By definition, the raps are "inside" the building and below the floor so the "heat" probably has to come from the downstairs area.

Gremlins are sneaky. When you show up with tools, ladders and service lights, they run and hide. It is only after you can't find a problem, pack your stuff up and drive away that they come back out again!