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So, one of the things I want to do around these parts is insulate (lag) the hot water piping in this house's basement to the best of my ability (especially since part of it is in a crawlspace that's opened up now, but not normally accessible). It's all 1/2" rigid copper, and I can get pipe insulation (straights and elbows) that fits that rather readily. However, while the straight sections I can get are of the self-adhesive seamed type, the elbows I can find are solid types that must be slit in the field and then attached somehow.

Normally, this is done with a contact cement; however, I can't use solvent-based cements for this due to the safety hazard they pose working around live gas appliances (water heater, gas furnace), and I cannot find water-based cements in small enough quantities for it to matter. (There are also methylene chloride based contact cements, but I want no part of MeCl2, given it's reputation for doing unkind things to people.) So, I am considering using a vinyl pipe-insulation tape to attach the elbow instead. Is this a reasonable thing to do, or will using tape wraps instead of the normal seam-cementing process compromise the insulation performance significantly?

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Try tape and do not wrap tight. And a couple of hose clamps to hold shape.On the elbows. And cable ties on the straight runs. Snug not pulled tight. Seam facing down.

  • Why upside down? On a cold water line, that'll drip condensation. – Mazura Jun 8 at 3:17
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    Have used before and the ones upside down last longer and did not come apart over time, gravity . – user101687 Jun 8 at 3:23
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    Seam down, the weight of the foam will hold itself hanging on the pipe, adhesive just holds the ends in the right place. Seam up, the cement or adhesive has to provide the tension for it, so it fails sooner (if it even sets properly in the first place). – Nij Jun 8 at 5:05
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If it has to be pretty, Frost King does make self-adhesive elbows and tees. And if it's not going to come slit and with glue, I'd just make my own out of straight sections (cut out a 90 degree section at a 45, almost entirely through; now it's an elbow).

The only unreasonable thing to do is to use that white tape on black insulation (it comes in black too). I'd have to assume that the additional insulation factor added by the extra tape would offset any losses due to a homemade slit; especially if it's hung according to Robert's specifications: 'snug, but not tight'.

If it's too tight you compromise the insulation. If it's too loose then that slit will lose more heat.

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