PEX debate...

[mrcaptainbob]

I installed an outside wood burning stove about four years ago and connected it to the hydronic heat system with PEX. I used the gray plastic compression fittings as was suggested. I am NOT pleased. Those will ALL be replaced with the crimp fittings this weekend. Had enough leaks from cracked or leaking fittings far too often. A fitting would crack after three years of use. Huh? 5 to 10 PSI water from 160* to 190* are the parameters. Fortunately I found a plumbing supply shop nearby that rents the tools for this. My opinion (unsolicited, I understand...), gray plastic fittings for compression fittings should be banned. I dare say wood would be a better choice!
Okay. I'm done.

[olddude]

I put a hydronic heating system into our new house, Watts oxygen barrier pex looped out of copper manifolds, heated with a natural gas boiler. By design the system runs 140-160 degrees and 19-20 psi. The pipe itself is listed at 180 degrees/100 psi and 200 degrees/80 psi. Its supported every 3-4 feet between the floor joists and expands/contracts but doesn't seem to sag when hot. I used the Watts cinch clamp system and have not had any problems in two years use. Downside the clamp tool is about $150 or so. It will work with 1/2 and 3/4 pipe though.

[mrcaptainbob]

Thanks, Olddude. I'll look into that stuff. Had some hiccups project-wise here the last week or so and haven't had the chance to replace the compression fittings. Hopefull this weekend.

[LazyPup]

MrCaptainbob..

For the record, the compression fittings ARE PROHIBITED for plumbing systems.

They are approved for HVAC use in some jurisdictions but for exactly the reasons you noted the use of compression fittings is discouraged by most trained HVAC techs and installers.

[Ultraone00]

Beware!! With any increase in temperature pressures within the piping expands. In closed heating systems there MUST be a compensation for that expansion. Older systems used a tank hanging from the floor joists above the boiler. Newer boiler systems have much smaller diaphram tanks hanging from or tucked between the joists. Fireplace grill / domestic water heating systems will indeed develope pressure and need the expansion tanks! Get one installed, drop the diaphram pressure as low the circulating pump can reach as head pressure and pay attention to any air-locks. Good luck!

[mrcaptainbob]

Here's a pic of some of the fittings. The gray with the radial crack certainly appears that I overtightened it. Followed the directions as far as torquing after the 'squeak'. It was good for three years. Suddenly started leaking and I found this. Had two others that were cracked longitudinally. Also, most of the compression rings came off in pieces all dryed out and cracked.
I can sure understand, LayPup, why it's not code to use them on plumbing systems. Replaced them all with the crimp connectors two weekends ago. Wen I'm comfy with their integrity I'll advance to the next step of installing the radiant system in the upstairs bath.

[KSever]

Found one of these same connectors like you have there Bob on a domestic water line at work (in a Hotel Commercial kitchen) on a 1/2" copper line. Cut all this out and replaced it with a normal copper connector. Who knows what the previous Chief Engineer was thinking. I still can't believe it held for as long as it was in there on this 80lbs of water pressure behind it.