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expansion tanks

Discussion in 'Plumbing Codes' started by pwood, Nov 16, 2010.

  1. pwood

    pwood Platinum Member

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    when exactly are expansion tanks required on water heaters? type of fuel,capacity, closed system?
     
  2. Jobsaver

    Jobsaver Sawhorse

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    In my ahj, whenever it is on a closed system. Our water purveyor does not install any type of device at the meter, so the utility is not a closed system. On the propert owner's side of the meter, if a RPZ, check valve, or other device is installed upstream of the water heater, an expansion tank, or expansion valve is required.
     
  3. texas transplant

    texas transplant Silver Member

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    From the 2006 IPC

    607.3 Thermal expansion control.

    A means of controlling increased pressure caused by thermal expansion shall be provided where required in accordance with Sections 607.3.1 and 607.3.2.

    607.3.1 Pressure-reducing valve.

    For water service system sizes up to and including 2 inches (51 mm), a device for controlling pressure shall be installed where, because of thermal expansion, the pressure on the downstream side of a pressure-reducing valve exceeds the pressure-reducing valve setting.

    607.3.2 Backflow prevention device or check valve.

    Where a backflow prevention device, check valve or other device is installed on a water supply system utilizing storage water heating equipment such that thermal expansion causes an increase in pressure, a device for controlling pressure shall be installed.
     
    #3 texas transplant, Nov 16, 2010
    Last edited by a moderator: Nov 18, 2010
  4. Uncle Bob

    Uncle Bob Sawhorse

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    Closed system

    Uncle Bob
     
  5. Glennman CBO

    Glennman CBO Silver Member

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    Agreed, closed system.

    Also, an expansion tank is not the same as a pressure relief valve. A pressure relief valve is always required, and an expansion tank is only required in a closed system.
     
  6. Mule

    Mule Platinum Member

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    We have a subdivision that has excessive water pressure so we require a pressure reducing valve. Now this doesn't make a closed system but since the pressure is higher on the incoming side than the outgoing we require an expansion tank.

    Our thought on this is even though the PRV will allow water to backflow into the city system when the water expands it will not because the pressure is higher on the city side. The water has to expand somewhere so...expansion tank.

    The reason I post this is because this type of system is not a closed system but in my opinion the circumstances create a situation where a expansion tank is needed.
     
  7. pwood

    pwood Platinum Member

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    thanks to all who responded for the help. texas t, are those ipc code sections?
     
  8. DanB

    DanB Member

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    The pressure reducing valves I've worked did function as check valves also. I would always require an expansion tank in the system if present.
     
  9. texas transplant

    texas transplant Silver Member

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    That is the 2006 IPC sorry forgot to say that before.
     
  10. Mule

    Mule Platinum Member

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    These actually do not so they "say" no expansion tank is needed. Common sense took hold and said in my opinion you need one.
     
  11. peach

    peach Sawhorse

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    probably always a good idea
     
  12. 88twin

    88twin Bronze Member

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    cpold be a dumb question... is it a closed system if there is a sprinkler sys. (irrigtion not fire)
     
  13. texas transplant

    texas transplant Silver Member

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    88,

    No, closed system with a water heater that would cause thermal expansion is where expansion control is required. We have a requirement that the irrigation system be isolated from the domestic water system with an RPZ, at a minimum,but since the sprinkler system has no water heater, thermal expansion is not an issue.
     
  14. Mule

    Mule Platinum Member

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    It all depends on where you install the backflow prevention device. If it is on the main sevice line going to the house, then yes it would be a closed system. If it is on a branch off of the main line then no, it is not a closed system.

    I remember a few years back, Denton, Texas I believe, started installing water meters with a backflow device. All of the older homes started having troubles. Joints started leaking inside the walls, yard lines were busting, all because of a closed system. The older pipes and joints could not take the additional pressure being created.
     
  15. 88twin

    88twin Bronze Member

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    thank you for the response. the debate here was if it was a closed system if it had a sprinkler

    line. I was getting out voted so I thought I'd "ask the experts".

    not that it will probably do any good in the debate , but at least I'll know.
     
  16. Dr. J

    Dr. J Silver Member

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    88twin - tell the debaters to look at the arrow on the backflow preventer. If it points toward the water heater - the expanded water can't get past it creating a closed sytem; if it points away from the water heater - open system.
     
  17. 88twin

    88twin Bronze Member

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    ahhh Dr.J, as you and fatboy know my city is at 6,000+ elevation.

    all the areas I have worked and played the last 35 years, if we had an

    irrigation system- open, no irrigation system AND rpv then closed.

    at this elev. it's common to close the ball valve and shut down the sprinklers for the winter so...

    now it's closed.

    never mind the fact there have been no NO problems or complaints for 40 years,

    "someone" just found the requirement in the code so it must be enforced.

    granted the better plumbers do use expansion tanks at W/H and the city is replaceing water meters

    throughout town, installing an RPV at all services.

    typical water pressure here is approx. 120psi, and has been for years.
     
  18. Mule

    Mule Platinum Member

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    88twin...see post #14 of mine above as to what happened when a city in Texas decided to install backflow preventers at the meter.
     
  19. Dr. J

    Dr. J Silver Member

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    The backflow preventer, and the ball valve to isolate the irrigation system do not make for a closed system anymore than the angle stops or faucets on each plumbing fixture. The "goes-outta" end of a building's domestic water system is always closed, it is the "goes-inta" that could be either open (allows expanded water back to the city main) or closed (prevents expanded water back to the city main).
     
  20. mtlogcabin

    mtlogcabin Sawhorse

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    A few years back the public works was getting complaints of exccessive water bills, They concluded that the newer homes without water hammers did not allow for expansion which the water heater was causings and was thus resulting in the water meter "rocking" back and forth. The meters only register flow in one direction. The solution was install an expansion tank and the problem was solved. So there are other reasons an expansion tank may be a good idea even on an open system
     

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