I'm trying to diagnose an air locking problem with a power shower. It's currently fed by 15mm white plastic (type unknown) pipes for both hot and cold. I'd like to replace these with clear rigid pipes so I can "see" if and where air is getting into the plumbing.

The defacto "clear rigid plastic pipe" material seems to be Acrylic (often going by trade name Perspex by online sellers). The most readily available dimensions are 15mm outer diameter x 11mm inner diameter, sold in 300mm lengths (which is adequate for the lengths I need).

What's the maximum temperature and pressure of water such a pipe will take?

My hot water pressure is I'm guessing around 0.3 bar as it's a single-story barn conversion with a header tank. The cold pressure is more of a concern as it's pretty good; I'm guessing around 6 bar.

  • I'd be concerned by the tendency of acrylic to craze and shatter, if this is to be left in place for a long time. Polycarbonate is stronger, flexes rather than failing abruptly, and has a softening point well above the boiling point of water. See eplastics.com/polycarbonate/clear-tube Jun 18, 2019 at 22:54
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    The existing white pipe is almost certainly CPVC, as regular PVC does not handle hot water well. Jun 19, 2019 at 0:25

1 Answer 1


Acrylic can handle 180F, and isn't rated for pressure. Clear schedule 80 PVC is rated for pressure, but can only handle 140F. Check out McMastet-Carr online if you want more material specs.

Maybe look at this problem from another direction? Air getting sucked into a water line typically only happens on/near the inlet side of a pump, so check around the pump inlet first. Often times it's from cracked PVC fittings or a leaky o-ring when I've seen it in pools.

Instead of looking for the air in the water line, intentionally pressurize the water line with air and look for where water leaks/mists from the pipe. Even without water in the line you'll be able to hear it it if you can't see it.

Depending on how large your system is, and how large of an air compressor you have, you may need to add shutoff valves to isolate parts of the line. Use a regulator if you don't want to pressurize everything to 100+ psi which is probably higher than the pressure rating of your pipe and equipment.

On the same note, you can do a pressure drop test to confirm its not leaking if you're trying to rule sections of pipe out.

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