Question about using PVC pipe

Discussion in 'Tankless Water Heater Forum' started by WildWildMidwest, Jun 22, 2009.

  1. WildWildMidwest

    WildWildMidwest New Member

    Messages:
    35
    Location:
    Racine, WI
    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. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,705
    Location:
    Chicago, IL
    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. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,154
    Location:
    New England
    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.
  4. 99k

    99k Radon Contractor and Water Treatment

    Messages:
    460
    Location:
    Fairfield Co.,Connecticut
    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.
  5. WildWildMidwest

    WildWildMidwest New Member

    Messages:
    35
    Location:
    Racine, WI
    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. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,360
    Location:
    Yakima WA
    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. WildWildMidwest

    WildWildMidwest New Member

    Messages:
    35
    Location:
    Racine, WI
    @ 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.
  8. FloridaOrange

    FloridaOrange Plumbing Designer

    Messages:
    1,317
    Location:
    SW Florida
    The vents can get quite hot. :eek:
  9. WildWildMidwest

    WildWildMidwest New Member

    Messages:
    35
    Location:
    Racine, WI
    Gary, point taken. It is about streamlining installation and trying to learn something in the process.

    I asked my local building supply store's plumbing section staff. They didn't think there was any problem intermingling PVC or CPVC with copper for domestic water pipes. The Watts filter housings are all plastic & acrylic, and Watts' own installation kits and valves appear to be CPVC. But I prefer to stick with quality brass valves whenever possible. Copper connections are certainly optimal, however 1" copper fittings are about 10x more expensive versus threaded CPVC and it's more time consuming to construct.

    I'm hearing consensus from you that, regardless of what my store's sales staff said, my shortcut probably isn't well advised. Most of the store staff seem to have no formal plumbing experience. I trust your opinion a lot more than theirs.
  10. WildWildMidwest

    WildWildMidwest New Member

    Messages:
    35
    Location:
    Racine, WI
    FloridaOrange,

    Navien water heaters are direct vented condensing units. They don't get nearly as hot as noncondensing heaters. According to Navien's Installation Manual:

  11. WildWildMidwest

    WildWildMidwest New Member

    Messages:
    35
    Location:
    Racine, WI
    I just spoke with my plumbing inspector. He agreed that CPVC is within code and it's no problem for cold water connections. I'm not sure what the temperature limits are. PVC is NOT within Wisconsin code for domestic water systems.

    Thanks to all for your help.
  12. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,843
    Location:
    Cave Creek, Arizona
    Pvc

    I do not know of any code which allows PVC inside the building. And using threaded PVC would be a disaster waiting to happen.
  13. WildWildMidwest

    WildWildMidwest New Member

    Messages:
    35
    Location:
    Racine, WI
    After considering the information here I decided to stick with 100% soldered copper pipe and fittings. While it's a little more work and money, I know soldered copper is the most reliable long-term solution. I purchased copper parts this afternoon.

    Thanks to all for providing sound guidance. Terry Love's Forums are a great source of plumbing wisdom and know-how!
  14. suavecito1177

    suavecito1177 New Member

    Messages:
    2
    Location:
    Denver, Co
    Codes in Denver say no PVC. CPVC, copper tubing and Pex are fine. I Prefer Pex and Sharkbite fittings for all my connections. Never have leaks and makes installation a breeze. Also for gas line I use Trac-pipe or Gas-tite, but you can't pick that up at your local hardware store. Usually install most tankless in under 3 hours.
  15. Scott D. Plumber

    Scott D. Plumber In the Trades

    Messages:
    67
    No PVC

    I would not use PVC even if it were allowed by code. (which it is not here in VA)

    Also, the stack temps are much lower in the Navien and that's why they let you use PVC for a vent. (Which I also Don't like)

    So what happens if you have hard water dn the HX begins liming up? When the efficiencies go down, you know what stack temps do? Yep, they go up! PVC for a tankless vent is a bad idea. But people want to do it anyway.

    Also, Don't forget your drain pan if it's going in a finished area! www.thewallsaver.com. I'm a tankless guy and I'm here to tell you that they all eventually reach the end of their life. Some sooner than others.

    Go with Copper, PEX, CPVC as allowed by code and your skill level. Good luck.
  16. WildWildMidwest

    WildWildMidwest New Member

    Messages:
    35
    Location:
    Racine, WI
    I plumbed our Navien 210A in 3/4" copper pipe this summer and it works beautifully! I skipped the flexible stainless hoses and plumbed directly to the tankless shutoff valves in 100% soldered copper. I spent many hours with the blowtorch, so the installation is solid! I hired a master plumber for $300 to do the gas hook-up. It took him almost four hours. I couldn't be happier with how everything works.

    Because of our very cold groundwater in Wisconsin, I installed the 210A downstream of our 25 year old 50 gallon AO Smith gas water heater which provides baseline pre-warming to 60 degrees. We never experienced any hot water shortage with this arrangement. Without the pre-heater, Navien's larger 240A would probably have been a better choice for our climate. Eventually I'll have to replace the AO Smith tank, but it's showing no sign of leaks or other problems.

    I understand de-liming is a routine part of tankless maintenance. All water heaters have some maintenance. Having installed a pair of 5 inch three-stage water filters upstream of the tankless inflow dramatically reduces the amount of debris entering the heater, and that hopefully improves our efficiency between cleanings. I haven't needed to change filters yet. I expect to get about 8-12 months between filter changes.

    I used 100% PVC venting. The discussion about high pipe temps is nonsense. The exhaust pipe hardly rises a couple degrees above basement room temp, which is around 60 degrees in the winter and 70 degrees in the summer. There is NO possibility of overheating the PVC vent. It's not even minimally warm to the touch.

    Our total gas bill for our family of four in October was $19 (including central HVAC heat.) We have a 2600 square foot home plus full basement. November's gas bill was $30 -- thanks in part to supplemental home heating with a wood stove. I estimate our Navien gas usage at around $10-15 per month. We'll have exact numbers next summer when the HVAC is off, since we don't have any other gas appliances besides the water heaters and HVAC. We average around 18 showers per week (2 adults, 2 kids) plus lots of laundry in our 20 year old Maytag washer, our dishwasher, and plenty of hot running taps. We live comfortably with no sweaters in the winter, no scrimping on showers or laundry. My wife likes a scalding 20 minute ~115 degree shower. Mine and the kids are 12-15 minutes at (I'm guessing) 105-110 degrees. Our Navien is set at the default of 120 degrees, so our delta temp is about 60 degrees above prewarming.

    I meant to post some photos of our installation here but didn't get around to doing it yet. Will try to make time for that soon.

    Again, we have no regrets about our Navien tankless water heater. It's been everything we hoped -- reliable, quiet, efficient and very smart. My only surprise is that we don't need the recirculator tank to avoid hot-cold stacking, so I turned it off. I guess there's no real downside to having the recirculator except more complexity and potential for future failure. I would probably buy the non-recirculating Navien model if I had it to do over, but it's a moot point now.
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