insulating underground water line

[Tickridgescott]

the water line i am burying from my spring to the cisterns should be 16" deep in my area. In some places I am only able to trench down 6 inches because of VERY HARD ground/rock. I need to make sure this does not freeze. Anybody know of a way to do this. It's probably 200 feet of line where this is the case.

scott

 

[Mikey]

All insulation does is slow the rate of heat transfer. If you aren't continually heating the line, either by running water through it, or by an auxiliary heat source, the line will eventually arrive at the temperature of the surrounding soil. If that's below freezing, well...

So, you could either circulate water through the line, or bury a heater cable with the pipe. There are probably other ways as well. If the ground is just hard, but not actual rock, rent a small backhoe and be done with it.

 

[Sponsor]

 

[Jadnashua]

THe pipe should be below the frost line...you can usually find out where that is from your local building department.

 

[Cass]

Insulation will help with preventing rocks from penetrating the water line, I might also bed it in sand to keep the rocks away. If you need to be 16" deep you need to go where ever you need to go in order to get the 16" which may not be a straight line to the house.

 

[Bill Arden]

You could change the depth of the frost line. Up here in MN, USA the normal frost depth is about 6 feet, But by adding 2 inches of Styrofoam you can reduce that to only a few feet.

The idea is that you lay the Styrofoam out so that it extends horizontally 4 feet in each direction. The width needed is dependant on how big of an item you are protecting since the frost will in my case still go down 6 feet on each side and it will go in at a approximately 30 degree angle.

So I would scrape down as far as you can, add the pipe, then add some fill to get a level surface, add the Styrofoam and then put whatever topsoil or fill you want to use to hide the Styrofoam. The Styrofoam must be covered since it degrades under sunlight.

 

[Molo]

Can he mound soil 16" above and to each side of it? Or maybe he's have to go furher out to the sides because of frost penetration patterns? This reminds me of a friend's cabin. He built it on sauna tubes filled with concrete, and didn't bury them far enough. He was wondering if he could just fill soil around the tubes to give the frost protection.

Molo

 

[Raucina]

Use the styrofoam but worry about ants unless it has boric acid incorporated into it.

Mound up dirt over it as indicated

Simply use standard pipe insulation of good quality and thick wall and make sure you have a small leak somewhere in winter

Get a bigger and better backhoe with a narrow bucket or a chainsaw type trencher with rock teeth. Better go deeper than 16 " if its rock as it will transmit cold better.

backfill with vermiculite

Do nothing and develop a larger leak in cold weather... maybe an ice rink?

 

[Bill Arden]

The previous post listed many different options.

Let me clarify them for an 18-inch frost depth.

1) Use the Styrofoam but worry about ants unless it has boric acid incorporated into it.
In your case you would only need 1 inch thick Styrofoam that is about 24 inches wide.
This is an expensive option at 200 feet.

2) Mound up dirt over it as indicated
At 200 feet long * 18 inches high by 24 inches wide, this is also expensive unless you can just push available rubble around.

3) Simply use standard pipe insulation of good quality and thick wall and make sure you have a small leak somewhere in winter.

In other words, have a small needle valve that uses water somewhere after the pipe run.

4) Get a bigger and better backhoe with a narrow bucket or a chainsaw type trencher with rock teeth. Better go deeper than 16 " if its rock as it will transmit cold better. Backfill with vermiculite for better insulation.

Check your local rental store for rates.

5) Use freezable pipe and keep the water flowing and add heat tape.

In other words, have a small needle valve that uses water somewhere after the pipe run.
The pipe could partly freeze but as long as you adjust the valve to keep the water flowing it will keep the ground warm.

Then use the electrical heat tape when needed to thaw it out.

 

[Tickridgescott]

tough to do some of those. I rented a trencher last weekend to install the pipe. It is a 1350 foot run. There is a 500 foot section that is a very steep drop through the woods and going down that hill with a trencher was really scary, especially on the slick mud. A backhoe or trackhoe would have been my preference but i was on that slope with a trackhoe 2 weeks earlier when i went down to develop the spring. It is unnerving to say the least when you are on a 11000 lb piece of machinery and you start to slide down the slope and you instantly respond by jamming the bucket teeth deep into the ground as you can and you still slide 2 more feet and there is 300 more feet of slope ahead of you.

A trencher was scary, but not nearly as bad. As it turns out, the majority of the areas over the 1300 feet i was able to get 20" or more. But the much of the rock happened during that 500 foot slope. In a couple areas i managed only 6" . I am going to rent a bobcat and mound dirt. The bobcat i am renting is on tracks. It is not nearly as slick when the ground is roughed up now.