Insulation For Evacuated Tube Solar Water Heater Piping

Q: I am remodeling a bathroom, and have inserted a couple copper pipes from the basement to the attic for use in the possible future addition of solar water heating. I am wondering what insulation would be most appropriate to put around these pipes before I wall them in. I understand these heaters deal in pretty hot water, so I am not sure that the standard foam insulation would be appropriate. Any experience in this?

A: Unless you plan on running a highly pressurized system (15 psi is only something like 245 deg), you're not going above the boiling point of water regardless of the efficiency of the collector. Therefore the standard black foam sleeving from the big box stores will work fine. I hope this plumbing is going through an inside wall. If you live in cold country and the pipe is in an outside wall the insulation won't keep it from freezing. It'll only slow it down a little. If we'd talked earlier I'd have suggested PEX instead of copper. Cheaper, easier to install, tolerant of moderate freezing and infinitely more durable in the face of contaminated water, what will be eventually circulating in that system unless you pay attention to water chemistry. Home Depot sells something called a "Shark Bite" IIRC. It's made of brass and will connect PEX to PVC, copper, or CPVC... maybe more. I've used a couple of those, as well as the plastic "John Guest" type push-in fittings that Lowes sells. The plastic ones are way cheaper, but not as versatile. If you have several scores or hundreds of joints to make, there's no doubt that the crimp rings are the way to go, especially if none/few of them are in tight spots. The crimp tool will easily pay for itself. For up to a few dozen PEX to PEX, or PEX to IP joints, the plastic ones at Lowes are the way to go. The fittings cost more than crimps, but there's no $100 crimp tool to buy. PEX - "John Guest" - IP thread/solder adapter - copper The Shark Bites come in tube to tube configurations as well as tube to pipe thread. I think their biggest advantage is the instance where you can go PEX - Shark Bite - copper

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