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  1. #1
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    Default Direct vented gas water heater

    Is it required to have copper tail pipes installed next to the direct flue to the exterior? One today had the copper on the cold water side but not the hot exposing the Pex. Also, it is required to have an expansion tank installed with these water heaters. This one did not.

    Thanks in advance!

    Jim

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  2. #2
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    Default Re: Direct vented gas water heater

    The direct vent flue does not get excessively hot, so I don't see that it would be a problem. However, your local regs may say something to the contrary.

    I have seen PEX directly connected to so many water heaters now that I am convinced it is not easily damaged by moderate heat. The exception would be a standard combustion type gas heater with a hot vent hood. Those need an 18" metal stub before the PEX.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  3. #3
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    Default Re: Direct vented gas water heater

    Quote Originally Posted by John Kogel View Post
    The exception would be a standard combustion type gas heater with a hot vent hood. Those need an 18" metal stub before the PEX.
    The requirement is 6" clearance to combustible material, and PEX is combustible, so a 6" minimum clearance to the vent (and draft hood) is required.

    If the pipes went vertical, and if the vent went vertical too, then 18" of metal pipe between the water heater and the PEX would still leave the PEX within 6" of the vent.

    Jerry Peck
    Construction Litigation Consultant ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  4. #4
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    Default Re: Direct vented gas water heater

    Quote Originally Posted by Jerry Peck View Post
    The requirement is 6" clearance to combustible material, and PEX is combustible, so a 6" minimum clearance to the vent (and draft hood) is required.

    If the pipes went vertical, and if the vent went vertical too, then 18" of metal pipe between the water heater and the PEX would still leave the PEX within 6" of the vent.
    Thanks, Jerry, that is what I thought. How about the expansion tank or valve?


  5. #5
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    Default Re: Direct vented gas water heater

    Quote Originally Posted by JIM MURPHY View Post
    Also, it is required to have an expansion tank installed with these water heaters. This one did not
    Typically, an expansion tank or a pressure relief valve, depending on the area. I think I recall some areas specified an expansion tank, not sure.

    Jerry Peck
    Construction Litigation Consultant ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  6. #6
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    Default Re: Direct vented gas water heater

    Thermal expansion protection has been in the code for many years, but around here, the AHJs have been slow to adopt it. So, I recommend checking with your AHJ to see if they have adopted the requirement.

    But, several (maybe most) water heater manufacturers require thermal expansion protection, so you should be on solid ground to recommend it.

    If you choose not to decide, you still have made a choice.

  7. #7
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    Default Re: Direct vented gas water heater

    A thermal expansion tank is required on the cold water supply to the tank if there is a backflow prevention device at the water meter or if the water meter has a built in check valve. This is referred to as a closed system. Another situation would be if there is a re-circulation line on the hot water as this would require a check valve thus making a closed system. On a open system as in most residential homes, any expansion of water caused by the water heater would just go back to the city water main.

    - - - Updated - - -

    Last edited by Gerry Pomanti; 12-31-2017 at 10:16 AM.

  8. #8
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    Default Re: Direct vented gas water heater

    Quote Originally Posted by Gerry Pomanti View Post
    Another situation would be if there is a re-circulation line on the hot water as this would require a check valve thus making a closed system.
    That is still an open system as there is no check valve or other restriction (such as pressure regulator, etc) as the system is still open on the supply side.

    On a open system as in most residential homes, any expansion of water caused by the water heater would just go back to the city water main.
    As would happen even with a hot water re-circulation loop in the hot-back-to-the-water-heater loop ... thermal expansion would simply push back into the supply the same as if there was not a hot water re-circulation loop.

    Some municipalities/water utility systems do not want that thermal expansion 'push back' of water into the main, as such, some municipalities/water utility systems require a thermal expansion control device anyway ... and that could be a thermal expansion tank or a thermal expansion pressure relief valve which is then drained to a suitable location.

    Jerry Peck
    Construction Litigation Consultant ( www.ConstructionLitigationConsultants.com )
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  9. #9
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    Default Re: Direct vented gas water heater

    Some municipalities/water utility systems do not want that thermal expansion 'push back' of water into the main, as such, some municipalities/water utility systems require a thermal expansion control device anyway ... and that could be a thermal expansion tank or a thermal expansion pressure relief valve which is then drained to a suitable location.[/QUOTE]

    That doesn't make any sense. If it's an open system the pressure is always that of the city water supply.

    With a hot re-circulation line you need a check valve on the cold water supply to the tank. This creates the closed loop and need for the exp tank. Every hot water tank has a temp and pressure relief valve for safety but the purpose is not to relieve excess pressure from thermal expansion.


  10. #10
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    Default Re: Direct vented gas water heater

    Quote Originally Posted by Jerry Peck
    Some municipalities/water utility systems do not want that thermal expansion 'push back' of water into the main, as such, some municipalities/water utility systems require a thermal expansion control device anyway ... and that could be a thermal expansion tank or a thermal expansion pressure relief valve which is then drained to a suitable location.
    Quote Originally Posted by Gerry Pomanti View Post
    That doesn't make any sense. If it's an open system the pressure is always that of the city water supply.
    Until each water heater heats the water within it, and when things are heated, water being one of them, the heated thing expands, which raises the pressure at the water heater, and, with all hot water faucets closed, there are only two places for the expansion of the water to go: a) back into the street supply; b) expand the tank itself (which is not a good thing, and is why T&P relief valves are installed, except that T&P relief valve are set quite a bit higher than supply pressure, so the first thing that happens on an open system (nothing blocking the water from going back out the way it came in) is for the thermal expansion to push water back into the supply line until the pressure is equalized with the supply line pressure (because the expanded water is now into a larger area)

    With a hot re-circulation line you need a check valve on the cold water supply to the tank.
    Nope, that's not needed, and rarely, if ever, installed (unless you are in an area which requires such a check valve) ... I've never seen one installed, nor ever heard of one being installed before either.

    The recirculation pump simply ties into the farthest hot water branch end (or as close to that as possible) and circulates that water back to the water heater, usually into the bottom tank drain, where that water is reheated and circulated back out the hot outlet from the water heater.

    This creates the closed loop and need for the exp tank.
    Yes, that would create a closed system from that check valve in, but I've never heard of a check valve being installed there before - anyone else in a place where installing a check valve in the cold water supply to the water heater with a hot water circulation system installed? Curious as to how many areas have that check valve.

    Every hot water tank has a temp and pressure relief valve for safety but the purpose is not to relieve excess pressure from thermal expansion.
    Agreed, that's what a thermal expansion tank or a pressure relief valve is necessary for thermal expansion - notice that I did not say T&P relief valve here, I said (see underlining I added this time):
    some municipalities/water utility systems require a thermal expansion control device anyway ... and that could be a thermal expansion tank or a thermal expansion pressure relief valve which is then drained to a suitable location
    Those two relief valve are two different animals and are for two entirely different purposes.

    Jerry Peck
    Construction Litigation Consultant ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  11. #11

    Default Re: Direct vented gas water heater

    Quote Originally Posted by Gerry Pomanti View Post
    Some municipalities/water utility systems do not want that thermal expansion 'push back' of water into the main, as such, some municipalities/water utility systems require a thermal expansion control device anyway ... and that could be a thermal expansion tank or a thermal expansion pressure relief valve which is then drained to a suitable location.
    That doesn't make any sense. If it's an open system the pressure is always that of the city water supply.

    With a hot re-circulation line you need a check valve on the cold water supply to the tank. This creates the closed loop and need for the exp tank. Every hot water tank has a temp and pressure relief valve for safety but the purpose is not to relieve excess pressure from thermal expansion.[/QUOTE]

    The expansion tank is there to prevent back flow into the municipal water supply. As always every jurisdiction is different but here is what the Illinois plumbing code says

    ftp://www.ilga.gov/JCAR/AdminCode/077/077008900I11300R.html


    Section 890.1130 Protection of Potable Water

    g) Installation of Devices or Assemblies

    7) Closed water systems with hot water storage shall have a properly sized thermal expansion tank located in the cold water supply as near to the water heater as possible and with no shut-off valve or other device between the heater and the expansion tank. Exception: In existing buildings with a closed water system, a properly sized pressure relief valve may be substituted in place of a thermal expansion tank. For closed water systems created by backflow protection in manufactured housing, as required in Section 890.1140(i), a ballcock with a relief valve may be substituted for the thermal expansion tank.


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