How to insulate a shallow water line

[briandestefano]

I am working on an office building project which has been completed, however the contractor installed the water line for the building sprinkler system approximately 36" below grade due to shallow bedrock. The frost line here is approximately 42" and the water within the sprinkler system will not be flowing unless there is a fire in the building, so we believe that there is a real pottential for the water within the line to freeze.

My question is: how can i determine an R-value for the soil above the water line? I plan on using this information to determine how much foam, preferably sprayed, to place around the sprinkler system distribution line. Thanks for any help.

 

[greggy]

Foam has low compressive strength to withstand the soil load and once wet it is ineffective. We have had success insulating buried shallow water lines with a refined asphalt derivative called Witcolite. Another brand is Dri-Therm. Both are coarse powders that you compact and have compressive strength for use beneath roadways. Place beneath and around the pipes to a 6 inch compacted thickness. We found it to be cheaper than a prefabbed spun-on fiberglas insulation and hard plastic jacket. Remember, insulation only slows down the rate of cooling of the pipe and contents and it does not prevent it, especially in a non-circulating line.

 

[Unotec]

Fire sprinkler? You are heat tracing it, right?

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying ” Damn that was fun!” - Unknown>>

 

[rconner]

[also, see thread at

http://eng-tips.com/viewthread.cfm?qid=217830

]