PEX in Trench w/ spray foam advice wanted

[foamit up]

GG and Shelterman I spaced the 1 1/4" pex lines with 1" sheet (pink) foam pieces about two inches long. One piece between pipes every two feet. Then i put a piece about 1" by4" by 4" on the outsides of the two pex pipes, all four sides. (You will have to experiment with foam size so that it has some space when sliding in the drain pipe.) Then duct taped the sandwich all around. This was done every two ft of pipe as i tried 4 ft but got to many sages.( so i thought) I wanted to make sure the pex was as close to center of the 6" flexible black pipe as possible. I tied the black pipe to a telephone pole and then pulled the pex in with a rope, i had someone at other end feeding it in. It was about 30degrees out when we did it so pipe was a little stiff. Worked a lot better the second time i did it when pipe was warmed up from the sun, 60 degrees. Foamit Up

 

[Tennman]

I will post a new thread about our foaming success and I'll figure out how to post pics. The hard part was of course getting out my failed first pex insulation attempt which we did with a Ditch Witch mini-backhoe. Absolutely no damage to the pex tubing. We lined the trench with 4 mil black plastic just to avoid dirt getting blown around and into the foam. We laid the plastic and from the time the foamer started spraying we were done in about 30 minutes to do about 160' of trench. Our goal was to get a minimum of 3" all around with about 2-3" of separation between the lines. Since at least 3" surrounding was my minimum, most of the time it ended up being as much as 5" in some places. We sprayed first under the foam onto the plastic, allowed to expand, then lowered the lines into the still expanding foam. Then the foamer sprayed on top multiple times so i ended up with I'd guess at least 4" on top. By having the trench open he could keep spraying where we saw small cavities. I probably ended up with a monolithic block of foam 10-11" wide x 7-10" deep. It was awesome and very fast. We were walking on the foam 20 minutes after we had completed the entire length. Based on my one-time experience, I would not mess with trying to enclose it in any type of protective pipe for fear of inadvertently creating voids. By spraying in the open trench my foamer was able to see cavities to paint with foam and totally enclose. Also because I was so adamant about minimum coverage, he was conservative and I ended up with much more insulation than planned. He estimated the average cross-section area and multiplied by the length to compute the cubic feet of foam to price the job. I ended up with far more foam around my pex than if I had gone with the stuff you get pre-done. Absolutely awesome process and results. This was the first time doing this for both the foam contractor and me and within 8-10' from when we started we were working as and team and getting better results than I had hoped for. Because we needed to use the mini-backhoe to get the pex out my trench was a good bit wider than necessary which added to my foam expense some. But I spend $800 to have this foamed. I bough the 1 1/4 pex as cheap as it can be bought per foot. Had I not screwed up and did my home brew approach first this would have been very cost effective vs going the prefoamed stuff. Bottomline.... this was easy, fast, way over insulated and Lord willin, done for the rest of my days here. This approach I highly recommend.

 

[Piker]

Congratulations!!... sounds like it was pretty a smooth operation. $800 clams for 160' sounds pretty decent too, especially considering the extra volume of foam you have in the ditch. Can't wait to see the photos.

cheers.