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Thread: Question about using PVC pipe

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  1. #1
    DIY Member WildWildMidwest's Avatar
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    Default Question about using PVC pipe

    I am preparing to install our Navien 210A tankless water heater soon. I will do the water pipe and electrical work myself, then hire a licensed plumber to complete the gas installation.

    My question relates to use of PVC pressure pipe. Our current domestic pipes are 3/4" soldered copper. I've done quite a bit of modification to our pipes over the years with L-grade 3/4" soldered copper. I recently installed a cycle stop valve, which works beautifully! I bought some decent quality 1" shut-off valves and a pair of 4.5 x 10" water filter housings to prefilter sediment upstream from our tankless heater.

    I wonder if there's any reason why I shouldn't connect the valves and filters using 1" white PVC pressure pipes and PVC cement? Is there any safety risk or code violation using PVC for domestic cold water pipes? Will cured PVC cement hold 45-62 PSI over many years without leaking?

    PVC would be a cost savings and would take about 1/2 the time to construct versus copper. I can use pre-threaded PVC pieces to make my job easier. I don't plan on using any PVC on the hot water side... just 3/4 inch copper. Thanks.

  2. #2
    Illinois Licensed Plumber SewerRatz's Avatar
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    I would double check with your local plumbing codes. Most cities around by me will not allow PVC or even CPVC to be used. The Illinois code does allow it,but like I said the cities themselves will not allow for it. Also I would not use PVC , if your plumbing code for your city allows you to use a plastic pipe you best off using CPVC.

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    In a conventional WH (may not apply with yours), you cannot use any plastic pipe within (I think) 18" of it. SO, if you have to use copper anyway, I'd probably go all the way. What, if anything does the installation manual say? You may also want to ask your building inspector.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #4
    Radon Contractor and Water Treatment 99k's Avatar
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    The IPC does not allow PVC but CPVC is allowed. It can be used for hot and cold, but as mentioned, stay away from the WH (nipples are sold in the supply store for this). The proper protocol for glueing CPVC is to allow a 24 hr cure time ... not likely to happen. I would use copper tubing or PEX.

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    DIY Member WildWildMidwest's Avatar
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    Thanks for all the feedback. I left a message for our town's plumbing inspector to call me back. He'll be doing our inspection when the heater is installed. I agree it's far better to get pre-approval before starting the work.

  6. #6
    In the Trades Gary Swart's Avatar
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    Even if plastic pipe is allowed in you area, why would you want to use an inferior medium? You apparently already know how to sweat copper, and that is a much better material than plastic.

  7. #7
    DIY Member WildWildMidwest's Avatar
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    @ jadnashua,

    I will use flexible stainless steel hoses for the last 24" to make future WH removal & servicing easier, so no plastic will be within 18" of the tankless unit. I'll go the extra mile and secure 5/16" cement board to the wall behind the tankless heater as an added fire barrier... which is probably unnecessary but it's only a few bucks. I understand tankless heaters aren't supposed to get hot to the touch. Navien recommends a minimum of 0.5" rear clearance. Just to be sure, I'll leave a 2-4" rear air space to maximize convection surface area and optimize free airflow.

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