NewB Seeking Feedback on Underground Piping Idea

[DeereMan]

Hello all. Been lurking for a while preparing for my install. I would love to run my underground pipes out of logstor or thermopex but at $12-$13 a foot I find it cost prohibitive. I love the ideas I have seen on here for foam I'm trench but there are not many options around here for contractors, one told me he charged $600 just to clean his gun. I've researched the Tigerfoam kits but know my luck, I would run out with twenty feet left due to my trench size varying.

I was thinking of putting a spin on the foam in trench method for my 150' run and wanted feedback. I am thinking of buying a 6" solid tile and then cut a 1" wide slit in the top from one end to the other using a sawzall. I would then use blue Styrofoam board and make pipe spacers to put every 3' to keep the pex in the currect location. This is something I have seen users on here do in their trenches. The one once slit is enough that I can spread the tile and get the pex and spacers inside. I would then fill with an expanding foam with the tile being no more than a mold that allows me to accurately control my volume. The foam would be applied through the one inch slit as well.

I am thinking of using the two part, pourable foam if I can find a slow rise product. It is cheaper to ship due to no hazmat.

I figured my 150 foot run at roughly 30 cubic foot which would require one $600 kit of the sprayable product and it looks like roughly $300 if pourable is used. If I'm figuring right I can do this for about $6-$7 a foot. Any thoughts would be appreciated

 

[BoilerMan]

Welcome the Hearth!

In commercial underground jobs I've worked on, they do something similar but only where a weld joint is. They use steel pipe which is insulated with urethane foam and a thick (1/4") polyethylene outer skin. About a foot from the ends the pipe protrudes and they weld it to the next pipe leaving a 2' gap of naked pipe. They use a poly cover and fill it with two part pourable foam after pressure testing the weld. Then the double heat shrink a sleeve over the joint for water protection.

We buried 4,000 feet of 4" pipe last month like this. Water protrusion of the foam is CRITICAL. You are essentially making your own Logstor, but the exposed gap in the drain tile is the problem where groundwater can get into the foam.

TS