Hi,

I am building a house where the frost can get deep (5 Feet). I wonder if the discharge line from the house can freeze if it is correctly installed with a 1/4 inch per foot slope. I imagine it will never sit full and should not there for freeze. I may only be able to get it down 3 Feet.

It will go to a existing septic tank where the inlet to the tank is only 30 to 36 inches from the surface.

Gord

I've been a Florida plumber for 50 years but when I worked at my fathers shop in Wisconsin we buried our sewer lines beneath the frost line. Perhaps one of my yankee experts has a different take on this. Regards, Tom

Hi,

I am building a house where the frost can get deep (5 Feet). I wonder if the discharge line from the house can freeze if it is correctly installed with a 1/4 inch per foot slope. I imagine it will never sit full and should not there for freeze. I may only be able to get it down 3 Feet.

It will go to a existing septic tank where the inlet to the tank is only 30 to 36 inches from the surface.

Well, unless you plan on burying your septic tank several feet deeper, it sounds like you're stuck with what you've got.

I've worked in some of the coldest parts of Alaska, and the usual freeze point isn't the sewer line itself -- The usual freeze point is right at the inlet to the septic tank.

What we generally did was slope our drainage lines 3/8" per foot, thus increasing the velocity of the flow.

But, because of power outages, storms that snowed us in while we were in town and other unforseen calamities, we also ran tempered water to the toilets and insulated the heck out of any p-traps in crawl spaces (usually bathtub and shower traps) and if we were going to be gone for a day or two, we shut the water off at the meter, drained the system and poured a half of a cup of glycol (antifreeze) into each sink, clotheswasher, tub and shower p-trap and a full cup of glycol into each toilet bowl and tank before leaving.

I'm not exactly sure where you're posting from, but I've weathered a few winters in Barrow, where your spit froze before it hit the ground.

I am in Canada, just north of Minot ND. Yes, I am stuck with the depth of the tank so unless it definitely won't work my plan is to dig out the trench and fill below the line with washed gravel then sandwich the effluent line in foam and fill above with washed gravel again.

I have read that keeping the fill as dry as possible reduces the heat transfer and therefor the ability of the frost to penetrate.

Thanks for the replies,

Gord