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Pex vs copper for hydronic heat

  1. #1
    Burns retinas nhbubba's Avatar
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    Pex vs copper for hydronic heat


    Had a bit of an issue with my house the other day. Came home from work to find it raining in my garage. Looks like one of the pipes in the heating system in the room over the garage froze. Then the water stopped and started freezing in the rest of the pipes. The more I peel back the more damage I find. Looks like the entire zone is popped pipes every 18-20" in the run. 2 of the 4 rads are split open. Real shit show. I'm in damage control mode now. I cut in ball valves to isolate that zone and get heat back to the rest of the house (2 more zones, plus DHW). Didn't get heat back until almost 11 that night, struggling to purge everything by myself. But it looks like I got 'er dun. House did not freeze solid.

    I had my heating/plumber guy in yesterday morning and he said I've done about all I can do in the short term.

    Upsides abound: I never used that room. (Part of the problem, I didn't notice the heat had failed in there because I never go in there.) The room is over the garage so all the water damage was in the garage; only durable (motorcycle, mostly DRZ and SV bits, nobody cares about that) stuff that got wet. Not a biggie. Also the walls were raw sheet-rock, not much finish to repair there. This weekend I'm going to open the walls up, air everything out and replace whatever insulation is ruined. I don't use the room and there is no other plumbing in those walls, so I don't need this fixed right now. Fortunately.
    Also this zone is relatively small; not much to replace, compared to the rest of the house.

    When I do get to it.. should I be looking to switch to a pex pipe product instead? Looks like I need to replace about 60' of pipe (run and return) minus radiators (2x 3', 1x 12'). Probably more if I have to chase pex back down into the basement.

    Is this worth it? Is Pex really that much more resistant to breaking from a freeze? Aren't the couplings just as susceptible to freezing?
    Can Pex be retrofitted where I have copper (and 90 bends) in existing walls? How much of a bitch is that?

    My guy made the comment that I "should have had antifreeze in there". I didn't even know that was a thing. Shit that's good to know now..

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  2. #2
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    Re: Pex vs copper for hydronic heat

    There are transition fittings to go from copper to Pex. Also, Pex can make the bends (just more gradual) in the stud/joist bay where the copper is doing the 90 and overall should have less connection fittings than copper. Similar as snaking a stiff garden house through the house. Generally, Pex is considered to be more freeze resistant than copper but is not freeze proof.

    At the end of the day its your decision based on factors such as cost, preference, difficulty/ease of installation, and time.

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  3. #3
    Your Father csmutty's Avatar
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    Re: Pex vs copper for hydronic heat

    Really. I've never heard of running antifreeze in there. I'll have to ask my guy about that.

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  4. #4
    High maintenance priss
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    Re: Pex vs copper for hydronic heat

    That sucks! Sounds like a royal PITA.

    My last house had Pex for the main runs & interconnecting the baseboard radiators, so I'd think you'd be able to use it to tie your existing stuff together. Pex should be cheaper and easier to retrofit and is a bit resistant to freeze damage. That said, if you have freezing problems I'd get that looked at too. Do you leave the thermostat for that zone on at least 50-55*?

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  5. #5
    Super Moderator TheIglu's Avatar
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    Re: Pex vs copper for hydronic heat

    I'd run Pex wherever you are replacing damaged stuff. SharkBite connectors can go from cut copper straight to Pex, push fit. Expensive, but easy and nearly fool proof.

    Pex, by the foot, will be so cheap compared to copper that it's going to make up for the more expensive connectors.

    If you are not using that room next winter, drain the zone and shut off the thermostat. Much easier than running antifreeze throughout your whole system (which reduces it's thermal efficiency IIRC, same as with a motor/radiator).

    I have garden hose fittings on the bottom of all my zones, alone with valves on both sides. My entire addition is Pex. I did it all myself. JUST GET PEX B, it's easier to run. Pex A is a bitch....

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    Burns retinas nhbubba's Avatar
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    Re: Pex vs copper for hydronic heat

    Quote Originally Posted by csmutty View Post
    Really. I've never heard of running antifreeze in there. I'll have to ask my guy about that.
    That's exactly what I said. Everyone I mention it to gives me the blank look "yeah, you didn't know that?!?"
    Shows what I know. Woulda/coulda saved a bit of a shit show.

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    Soul Rider Paul_E_D's Avatar
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    Re: Pex vs copper for hydronic heat

    I have antifreeze in my system...thank god. I have crappy insulation.

    And I would definitely go to pex, if nothing else to make any future fixes tool-less and simple

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    Last edited by Paul_E_D; 03-17-17 at 11:54 AM.
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  8. #8
    BMW track whore e30addict's Avatar
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    Re: Pex vs copper for hydronic heat

    Quote Originally Posted by nhbubba View Post
    That's exactly what I said. Everyone I mention it to gives me the blank look "yeah, you didn't know that?!?"
    Shows what I know. Woulda/coulda saved a bit of a shit show.
    Put me in the wtf camp. I've never heard of doing that either. As Clayton mentioned it reduces efficiency but I have no clue how that translates to increased fuel cost.

    I'm sure there's plenty of math that could be done to calculate it but I'm way to lazy for that. I'd think better insulation would be more cost effective in the longer term in any case.

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    Burns retinas nhbubba's Avatar
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    Re: Pex vs copper for hydronic heat

    Quote Originally Posted by TheIglu View Post
    I'd run Pex wherever you are replacing damaged stuff. SharkBite connectors can go from cut copper straight to Pex, push fit. Expensive, but easy and nearly fool proof.

    Pex, by the foot, will be so cheap compared to copper that it's going to make up for the more expensive connectors.

    If you are not using that room next winter, drain the zone and shut off the thermostat. Much easier than running antifreeze throughout your whole system (which reduces it's thermal efficiency IIRC, same as with a motor/radiator).

    I have garden hose fittings on the bottom of all my zones, alone with valves on both sides. My entire addition is Pex. I did it all myself. JUST GET PEX B, it's easier to run. Pex A is a bitch....
    Types of PEX tubing (A, B, C). Choosing the right type and brand for your project.

    This says B is stiffer than A.

    Three rads and 2 cross connects to copper in the basement. Should mean 8 connectors total. A 100' bail of pipe should be more than enough, I think. I just looked it up and with home-despot pricing looks like pex is about 50% the cost of straight copper. Guy at work insists there are clamps for getting the pipe to do turns. The only challenge would be getting it pulled I guess.

    I'm installing ball valves and ball valve drains all over the fucking place now. This sucks.
    I've also never been able to purge the system to my satisfaction. Isolation valves will help with that. Apparently my system is the cheapskate design. Everyone at work (richy-rich massholes) claims their installs have valves everywhere.

    How are you sure a zone is drained? Do you have fixtures to blow them out with air?

    - - - Updated - - -

    Quote Originally Posted by Paul_E_D View Post
    And I would definitely go to pex, if nothing else to make any future fixes tool-less and simple
    How so?

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  10. #10
    Senior Member MHenry600's Avatar
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    Re: Pex vs copper for hydronic heat

    Quote Originally Posted by TheIglu View Post
    I'd run Pex wherever you are replacing damaged stuff. SharkBite connectors can go from cut copper straight to Pex, push fit. Expensive, but easy and nearly fool proof.

    Pex, by the foot, will be so cheap compared to copper that it's going to make up for the more expensive connectors.
    This is exactly what I was about to type up, too. No reason to not use Pex.

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  11. #11
    Burns retinas nhbubba's Avatar
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    Re: Pex vs copper for hydronic heat

    Quote Originally Posted by e30addict View Post
    Put me in the wtf camp. I've never heard of doing that either. As Clayton mentioned it reduces efficiency but I have no clue how that translates to increased fuel cost.

    I'm sure there's plenty of math that could be done to calculate it but I'm way to lazy for that. I'd think better insulation would be more cost effective in the longer term in any case.
    Apparently they pump it into the system once its charged. Another supposed side effect is that it can keep the system from corroding. Far better than straight well water, which is what my system eats right now.

    What really, really pisses me off is I paid a guy to do an energy audit and fix a bunch of insulation woes in this area a couple years ago. He cut holes into those eves and crawled in there to back the knee walls with tyvek to cut down on the air infiltration. Would had have fucking killed him to point out that there was insulation MISSING from parts of the stud bays? Or, you know, maybe fix that?!

    Anyway. I'm not bitter.

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  12. #12
    Burns retinas nhbubba's Avatar
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    Re: Pex vs copper for hydronic heat

    Quote Originally Posted by MHenry600 View Post
    This is exactly what I was about to type up, too. No reason to not use Pex.
    My reason not to is routing through existing construction. If I have to open more walls to do this... Well, that would be a reason not to.

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  13. #13
    Burns retinas nhbubba's Avatar
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    Re: Pex vs copper for hydronic heat

    How do you hook to radiators? How do you go from a 2x6 wall cavity to a radiator mounted on the other side of the drywall? 3/4" pex can't possibly radius that tight. Can it?

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    Burns retinas nhbubba's Avatar
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    Re: Pex vs copper for hydronic heat


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    Burns retinas nhbubba's Avatar
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    Re: Pex vs copper for hydronic heat

    Would need to add ~$100 to the project just for the tools. Unless anyone in my 'net has a crimp tool they'd lend me for a week or so?

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    Super Moderator TheIglu's Avatar
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    Re: Pex vs copper for hydronic heat

    You can get elbows, same as copper.


    Pex A, B, C. Whichever one I used was the hardest one to work with. Running hundreds of feet of it in loops under my floor sucked. Def tested the marriage doing that work with my wife.

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    Last edited by TheIglu; 03-17-17 at 12:18 PM.
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  17. #17
    Burns retinas nhbubba's Avatar
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    Re: Pex vs copper for hydronic heat

    So you do an elbow out of the wall into the baseboard? Okay. That makes sense.

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    Re: Pex vs copper for hydronic heat

    Just replace all damaged segments with pex. Once in place it is a click an play system. Only crimps are at pex to copper junctions. If you can borrow a good crimper, it is literal seconds to install a junction.

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  19. #19
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    Re: Pex vs copper for hydronic heat

    I was always advised against using antifreeze in a heating system. You'd think it would prevent corrosion, but it does not! It's actually worse and becomes very acidic after a year or 2. In other words if you use antifreeze, you have to flush and replace it every other year. It's not cheap, around $400 for a 5 gallon bucket.

    I'd always go pex with any future work, plumbing and heating. If you have well water, that is slightly acidic/hard, the water is slowly eating away your copper pipes and solder joints. You may not think that's a big deal... but what's in the pipes, is in the water. And if your copper plumbing is pre 80's, you're drinking copper and lead. Something to think about!

    I currently don't drink or cook with the water at my house because of this, the water has tested high on both lead and copper.

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  20. #20
    Burns retinas nhbubba's Avatar
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    Re: Pex vs copper for hydronic heat

    Water tests (from tap) are okay. House was built in 1987.
    I'm using the lead free solder.

    That said this is the heating system. Won't change anything to do with my drinking or showering water.

    You guys are making me want to do this with pex.. and do it myself. What the hell, I love (another) project.

    Where do you buy your pex supplies, baseboards, etc? Not the despot I imagine.

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  21. #21
    Senior Member MHenry600's Avatar
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    Re: Pex vs copper for hydronic heat

    Quote Originally Posted by nhbubba View Post
    My reason not to is routing through existing construction. If I have to open more walls to do this... Well, that would be a reason not to.
    I see. I was reading it as replacing just the blown out copper pipe in the already exposed section.

    If the remaining copper is still in good shape, you can just Sharkbite where the damage begins and run Pex for the replacement section.

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  22. #22
    Lifer jasnmar's Avatar
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    Re: Pex vs copper for hydronic heat

    Pretty sure I have a crimper.

    Heating system in my house is copper in the basement, then transitions to pex for the runs. I didn't put it in, but that's the way it is set up.

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  23. #23

    Re: Pex vs copper for hydronic heat

    I did over all 7 units of my apartment building in PEX and is the only way I'd go moving forward. I have the tool and you're welcome to it for as long as you need... but I am in the Palmer, MA area?

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  24. #24
    Awesomeness, Inc. MattR302's Avatar
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    Re: Pex vs copper for hydronic heat

    Been there, my house was foreclosed when I bought it, the water was off, the faucets/plumbing was winterized, but not the baseboard heating system.
    First off, borrow as many dehumidifiers as you can, run them in that room and the garage until it dries out.

    If you're replacing the entire loop, sure, have at it with the PEX.
    Before you go crazy planning out the PEX though, count how many breaks there are, figure out how much it would cost to splice in new copper to fix the breaks.
    3/4" straight couplings will cost ~$.75 each. Looks like a 10' length of 3/4" is under $20.
    If you have 20 breaks, and you could fix each of them with a 6" splice, that's only $30 in couplings and $20 of pipe. Obviously, the actual numbers will be different, long straight sections with multiple breaks might be easier to just replace it as a whole, etc. But if you're not messing with any elbows, replacing pipe thats good, no expensive PEX fittings, it might be cheaper to splice in copper.

    Radiators I'd be tempted to just cut out the broken sections and splice in a joint, depending on how many breaks in those lengths.
    I've got probably 20-25' of extra baseboard radiator in my garage you're welcome to have, if bychance you find yourself down this way.

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  25. #25
    Lifer
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    Re: Pex vs copper for hydronic heat

    I like pex and have it installed in some of my houses but not all. Why not all you may ask? Because mice like pex and I don't put it in places that I know have mice. I had way to many call backs on installs I did that were the result of mice chewing on it. I'm told it's a combo of the water movement and occasional condensation that draws them to it.
    If you don't have mice it's the best thing going. It takes a lot for pex to burst but it does swell like crazy to give you a little protection factor. Try not to lock freeze prone sections into tight spaces, let it have room to expand if needed. Also switch to a glycol system while your there. it does nothing for your drinking water parts but it should make the heating system worry free. You can leave the good copper in at that point.

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