Insulating an Underground Water Line

With the trench dug between my two structures, Grandpa was chomping at the bit to get the lines between both footings laid in and the trench filled in. We had a few rains which filled in the trench, requiring either bailing, or, in my lazy case, a siphon line with two garden hoses.

At its deepest, the trench was about three feet deep. F!, while digging it, seemed to think that at that depth we were close to being below the frost line. Unfortunately, at the sauna end, it rose up above ground level over the course of about six feet, and at the cabin end, it rose onto a rock plateau about twelve feet out, and then up to the footing in the last two or three feet.

To mitigate this, I decided to try to take a few steps to help as best as possible. First off, I wanted to have the option to change out the water line if it ever became unsuitable. To accomplish this, I laid down a non-perforated drainage tile as an overall conduit between the buildings. This also gave me a chance to run my electrical lines with the same flexibility. I decided to try them first. Shoving my 1″ poly pipe through the drain tile proved to be a challenge. Not impossible, but Grandpa had to follow along as I shoved from one end, shaking the tile to allow the pipe to pass the ribs. We got the poly pipe through, and with my fish tape and some dish soap, were able to easily pull through two 14/2 wires. One of these should supply power FROM the cabin, to the sauna during normal solar conditions. The other should supply power FROM the sauna to the cabin, when I decide to run the generator to charge up the batteries in winter time. This will allow me to run the generator on the far side of the sauna, hopefully shielding the cabin from the drone of the generator while it charges.

Grandpa, in an ever so clever move, carved out a “torpedo” from a nearby branch that was about an inch in diameter, and we duct taped this improvement to our actual waterline poly pipe. This pipe was twice as long as the drain tile and the electrical conduit (poly pipe). I wanted to run this pipe directly to the water tank in our sauna, and as close to the cabin sink as possible, before having to put in a coupler. Every coupler respresents a loss in flow and efficiency.

After feeding in about twenty-five of the one hundred foot line, I attached a gutter/eaves trough heating cable to the pipe with cable ties about every eight inches. This was my “nuclear” option for dealing with a frozen water line – I could run the generator, or perhaps on an exceptionally sunny day use my battery bank, to thaw the line with the heat cable. It is sixty feet long and draws about 300 watts. This is a considerable amount to run for any length of time, but compared to the alternative…

With both these lines run, it was time to take some passive measures. I purchased a number of sheets of 1.5″ closed cell foam suited for direct contact with soil and water, and cut them into six and twelve inch strips. The six inch strips I placed under my drain tile in all but the deepest part of the trench. Then I placed two twelve inch ones over the pipe from one end to the other. Again, using duct tape to hold them together in a sort of “A” frame, I squirted some “Great Stuff” expanding foam along all the seams and joints to seal it up.

Grandpa shoveled soil against this foam, completely covering it in the deepest part of the trench. After this, he made one more trip to my gravel/clay pit down by the well and topped up the trench with more fill. At this point, the trailer blew out a bearing again, and he decided that was enough for now. Besides, I had returned to work on the sauna itself, and my electrical cords and workspace had spilled across the path the tractor had to take.

I will place some more sheets of foam over the “A” frame as we build up the soil, probably just laying them flat and extending out some distance to either side. Then a light layer of soil over them to hold them in place, and we’ll hope for the best come winter!

Working in my favour hopefully are the following:

  • The line is deep in the trench for a good distance, hopefully at or below the frost line.
  • The line has an airspace insulation all around it in the form of the non perforated drain tile.
  • The drain tile has at least an inch and a half of closed cell foam insulation all around it for the entire distance.
  • The drain tile will also get another inch and a half to three inches of additional foam insulation where it rises up to the footings.
  • I can fall back on using the eave/gutter heating cable if it does freeze up.
  • If we take regular saunas, the water that will run from the sauna to the cabin may be significantly warmer than regular groundwater.

Only experience will tell how things really work out for us though. Much depends on just how warm the sauna gets, and how long it holds that warmth after the fire goes out. I’m sure I’ll post a notification when (or should I say if?) the water line does freeze up.


Leave a comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.