CPVC threaded fitting failure

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BostonGuido

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CPVC-fitting-solarHW.jpeg

So this 3/4" CPVC fitting was threaded into a Cu fitting in my attic, in the solar hot water loop. It let go with a bang on a nice sunny day with the circulator running and fortuately I was home to turn off the water. The actual domestic hot water is circulated throught the solar panels, it's not a separate loop. As it was there was a lot of water that came out, maybe 20-40 gallons, and fortunately mostly ran out (through light fixtures, bubbled paint, ... Had to replace wet insulation and replaced the fitting with a SharkBite. Question is, how did this occur? Pressure in well pump tank is 45 psi max.
 

John Gayewski

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A solar panel can make water/ steam over 300 degrees. There should be a way for your system to relieve pressure and or drain itself. CPVC isn't what I'd call a good material for a system capable of so much heat.

cpvc-male-adapter-terrylove.jpg
 

Jeff H Young

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I'm not sure off hand proper use of a plain male adapter on CPVC generally the ones with metal threads are used I suppose non pressure applications or cold only but I've never used one of those its been a long time since I used CPVC but I would either get rid of those adapters or check the spec I'm almost positive they are no good for hot
 

BostonGuido

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A solar panel can make water/ steam over 300 degrees. There should be a way for your system to relieve pressure and or drain itself. Cpvc isn't what I'd call a good material for a system capable of so much heat.
There's a TP valve on the water heater tank (ground floor utility room, no basement). Yeah, in hindsight I agree with you but it's in the house now. There was a second TP valve on the top of the solar panel years ago and it blew because of user error - left the panel full of water but circulator pump off on a sunny day. TP blew. Replaced with cap.
 

John Gayewski

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There's a TP valve on the water heater tank (ground floor utility room, no basement). Yeah, in hindsight I agree with you but it's in the house now. There was a second TP valve on the top of the solar panel years ago and it blew because of user error - left the panel full of water but circulator pump off on a sunny day. TP blew. Replaced with cap.
Well then it looks like the ruined threads on this fitting is also user error.
 

BostonGuido

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Not quite sure I follow. System was in normal operation this time. The user error was shutting down the system circulator pump with water in the panels when the panels should have been drained for shutdown. How is it user error for this fitting to blow? You could perhaps argue it was plumbing system part selection (i.e., design) or installation error...
 

John Gayewski

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Not quite sure I follow. System was in normal operation this time. The user error was shutting down the system circulator pump with water in the panels when the panels should have been drained for shutdown. How is it user error for this fitting to blow? You could perhaps argue it was plumbing system part selection (i.e., design) or installation error...
The relief valve that was plugged would be an error.
 

BostonGuido

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OK, I'll give you that. Possible that the temperature on the hot (outlet) side of the solar panel exceeded what CPVC fitting could take and by the time the water it got down to the tank it had cooled down some and did not blow there? Pressure is not particularly high (at 45 psi) but the CPVC softens at higher temps and...
 

Jeff H Young

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180 degrees max temp , whatever it takes to stay below that temp. or repipe it with rated pipe use CPVC to brass transition fittings on hot water I'd replace all standard male adapters on the hot with those transition adapters
 

Fitter30

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Solar system really needs a drain back system to regulate the water temp where at a certain temp water is drained from the panels to a holding tank to stop the heating.
 

Michael Young

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A solar panel can make water/ steam over 300 degrees. There should be a way for your system to relieve pressure and or drain itself. CPVC isn't what I'd call a good material for a system capable of so much heat.

cpvc-male-adapter-terrylove.jpg

100% agree with John. Replace it with machined fitting with metallic threads. Read your glue bottle. Give your joint plenty of time to cure. And honestly, if that water/steam is getting 300-degrees, I would replace that shit with type-L copper.
 
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