I foamed my lines in a trench. The depth really isn't a concern with foam. I went about 3' most of the way with the last 20' of my run only about 18" below ground level due to my septic tank. All I did was drape plastic in the trench, lay my lines in there, and lifted and foamed them in place as I went. I wrapped the foam in the plastic when done, but it was only there because it made foaming easier and kept out the dirt during the process. The foam is closed cell foam and therefore water is not a concern. The foam worked best for me since I had to punch a hole through my rock wall foundation to bring the lines in the house and spraying the foam let me seal that hole up as I went.
I'm not saying that foaming in place is the best method, it's just what I used. Use a quality product no matter what you do. You don't ever want to dig that line up to fix a problem. The extra upfront cost is worth it in the long run. Since I used 1-1/4" PEX, foaming in place was significantly cheaper than buying a quality pre-made product.
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Topic: Foaming the trench (Read 6525 times)