For a myriad of reasons too long and embarrassing to go into, I need to redo my underground boiler piping, self-installed using the tried and true, sure to fail, and it did, method of wrap and stuff into a 4" drain tile. I've finally found an experienced, very accomodating, and reasonably priced closed-cell, spray-foam contractor, referred by past customers, who has used varying methods to do this. His current preferred method for my situation is to " leave the pipe in the tile and foam everything in place, in case you want/have to pull new lines, and the tile will be a last resort moisture barrier if the foam cracks, moves, etc." I need to say that we've discussed the closed-cell, lbs/cu.ft. density, etc., and he knows his stuff, and I know that this equates into more foam applied/money for him, but I have no problem with this if I get the best result. I'm not sure of the validity of his argument, from 2 points. First, even if I wanted to, in order for me to pull lines through I would have to for sure break loose and straighten-out 8 ft. of each end of the 4" tile to do this, and I'm thinking there goes the integrity of the continuous insulation covering. Second, maybe I would no longer have a 4" hot water pipe in the ground, but would for sure have a 4" hot AIR pipe, which is open on each end into the boiler room and house. My gut feel is that for best insulating, I would want the foam right at the tubing? The 4" tile would offer some last-ditch protection to the tubing, but is this needed, and would I give away btus for this? For me, I'm leaning towards doing my due-diligence to the trench and tubing preparation, get rid of the drain tile, and foam around the tubing only. I think the likeliehood of having to put in new tubing is pretty remote, and if I ever had to, I would just dig up and replace as needed. What do you think? Thanks!
Underground pipe redo
- Thread starter 55Razor
- Start date
-
Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.
We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.
We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
- Status
heaterman
Minister of Fire
I wouldn't put it in regular corrugated drain tile. The wall strength is not sufficient IMHO. If you want a conduit, use a gasket joint or sovent weld type rigid pipe that will retain it's integrity for life. Water intrusion into the corrugated stuff is a major issue.
Medman
Feeling the Heat
I think you should remove the drain tile and do the foam directly on the water lines. If you think you will need conduit for other purposes in the future, install a black ABS line or PVC conduit in the trench once it is open.
Doing the foam directly on the lines gives you the opportunity to properly space them apart so that there is no heat transfer from the hot supply pipe to the colder return pipe. Also, you would be able to ensure that there is an adequate depth of foam surrounding each water line, guaranteeing you would not be losing heat to the surrounding soil.
If you are going to open the trench again anyway, you might as well do it right. I know I regret not putting in the conduit when I put in my lines; I may still have to dig the trench again to do this.
Doing the foam directly on the lines gives you the opportunity to properly space them apart so that there is no heat transfer from the hot supply pipe to the colder return pipe. Also, you would be able to ensure that there is an adequate depth of foam surrounding each water line, guaranteeing you would not be losing heat to the surrounding soil.
If you are going to open the trench again anyway, you might as well do it right. I know I regret not putting in the conduit when I put in my lines; I may still have to dig the trench again to do this.
Tennman
Minister of Fire
Razor, your gut is telling you the reality of the physics. Spraying the foam directly the tube minimizes the 3 ways thermal energy can move. I've heard the concern about cracks in the foam. I really could care less about a tiny sliver of water contacting my pex every so often in its length. The thermal transfer potential of a tiny crack filled with water is in the energy loss noise of the whole system. The odds of replacing your pex in your lifetime are very remote (unless your 10 years old). The energy loss over your lifetime putting pex in a conduit are enormous. FYI, a kissing cousin of this foam is sprayed directly on the aluminum skin of the Space Shuttle External Tank (BX 250 polyurethane) to keep heat out. Affectionately called ET. Go with your gut.
Thanks for the replies. I'm going to foam-in-place without the 4" tile; just makes more sense. I'm looking forward to seeing how much of a difference well insulated tubing will make!
Tennman
Minister of Fire
You'll be amazed. I presume you've read my horror story in the underground sticky. When I did my redo I hired a local guy who had a mini-backhoe. His bucket happened to be 12". Well that's certainly wider than I needed but my pex is in a block of nearly 12"x12" with at least 3" between the tubes. My heat loss over my ~180' run where I exit my boiler barn and enter the HX is really unbelievable but my AZEL sensors I use to measure transit losses don't lie. Best Wishes.
- Status
Similar threads
