Shutoff Valve in Hot Water Line of Water Heater

Discussion in 'Water Heater Forum, Tanks' started by aaronm, Dec 14, 2008.

  1. aaronm

    aaronm Inspector

    Messages:
    1
    Location:
    Garland, TX
    Is there any model code, manufacturer's installation instruction, or just plain reason that prohibits the installation of a shutoff valve in the hot water line coming out of the top of a water heater?
  2. Verdeboy

    Verdeboy In the Trades

    Messages:
    2,051
    Not that I know of. Many HW tanks have shutoffs at both the inlet and outlet.
  3. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,397
    Location:
    Yakima WA
    You should put a valve on the hot water line so that you can flush the tank without washing crud into it. One on the cold intake side isn't so useful, but with one, you could remove the tank without turning off the entire house water, and it's cheap enough to do. I use full flow ball valves.
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,263
    Location:
    Cave Creek, Arizona
    valve

    Some, not "many", water heaters have valves on both side. I run across ONE every ten years or so. And the one on the cold side is REQUIRED by all codes, even though someone says it is "not useful".
  5. Verdeboy

    Verdeboy In the Trades

    Messages:
    2,051
    Most of my previous experience is with larger tanks used in apartment buildings. They almost always have two shutoffs.

    Recently, however, most of the residences I have worked in have zero shut-offs, which means no water until their tank is replaced (or until I install the CW shutoff).
  6. Ian Gills

    Ian Gills Senior Robin Hood Guy

    Messages:
    2,777
    Location:
    USA
    Are all of you completely mad? Or is it 1 April?

    Even a DIYer knows this one, which says something.

    It is incredibly dangerous and absolutely against code to have a shut-off on both the inlet and outlet of a hot water heater. If both are closed, the WH relies completely on the proper functioning of the PRV to deal with pressure/expansion changes and faults if the heater is left on.

    If the PRV fails, then we start to see explosions of the type some of you post links to on this site every now and again.

    My neighbor has valves on both the inlet and outlet of his WH and I live in fear. Say he shuts them both off and forgets and the PRV fails?

    Shut-offs on WHs should only be installed on the cold side. That way, the fixtures and fittings (think washer hoses) of the hot supply will also take the strain of any increase in pressure should the PRV fail and there is fault with the WH. There is therefore less chance of a boom.

    How many bombs are you guys making?

    LONG LIVE D.I.Y.
    Last edited: Dec 16, 2008
  7. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,397
    Location:
    Yakima WA
    Regarding my statement that the valve one the "cold side wasn't as important etc.. My bad!!:eek: I certainly meant the valve on the HOT side was not as important as on the intake (cold) side. Thanks to HJ for catching my error!
  8. Ian Gills

    Ian Gills Senior Robin Hood Guy

    Messages:
    2,777
    Location:
    USA
    I cannot believe we are still sitting here entertaining this very idea.

    Am I dreaming?

    Or have I died and been reincarnated into a new world where there is a different plumbing code as well as a new law of physics?

    Or both?

    Two shut-offs on the outlet and inlet of a WH equals a potential boom. Period. Don't do it. Shut-offs, like expansion tanks, should only be installed on the cold side.
    Last edited: Dec 16, 2008
  9. Verdeboy

    Verdeboy In the Trades

    Messages:
    2,051
    Take it easy, man. You are the one about to explode.
    The only reason anyone would shut off those valves is to do maintenance or to replace the tank.

    And, even if both valves are closed while the tank is fired up, in order for it to become a bomb, both the thermostat and the T&P valve would have to fail.
  10. Ian Gills

    Ian Gills Senior Robin Hood Guy

    Messages:
    2,777
    Location:
    USA
    I am cool.

    Just trying to invoke some passion and debate.

    I get as good as I give on here anyway.
    Last edited: Dec 16, 2008
  11. kingsotall

    kingsotall Plunger/TurdPuncher

    aaronm, is there any particular reason you were asking or were you just wondering¿
  12. Probedude

    Probedude New Member

    Messages:
    137
    Location:
    CA
    Think of it this way in regards to the water heater being a bomb if the inlet and outlet were shut off and the TPV failed
    - how is this different than if the inlet were shutoff and no other hot water fixture in the house was turned on? It's still a closed system.
  13. Ian Gills

    Ian Gills Senior Robin Hood Guy

    Messages:
    2,777
    Location:
    USA
    You have washer hoses, copper fittings and all sorts of other fixtures that will probably fail before the water tank does.

    Not to mention you might notice the problem in the chance you open a tap.
  14. Ladiesman271

    Ladiesman271 Homeowner

    Messages:
    221
    I have a shutoff valve on the cold side as well as the hot side of my water heater. The T&P valve is between the hot water output of the water heater and the hot water shutoff valve.


    Works fine!
  15. Ian Gills

    Ian Gills Senior Robin Hood Guy

    Messages:
    2,777
    Location:
    USA
    Again, I raise an objection.

    If a licensed plumber installed a shut-off on the hot side of my tank I would be extremely disappointed, and tell him to remove it.

    Of course he wouldn't because they all want to save a few bucks on fittings.

    But more importantly it is against code.

    I am more than slightly surprised that a few of the pros around here are not jumping in and backing me up on what is a basic safety issue.
    Last edited: Dec 18, 2008
  16. Ian Gills

    Ian Gills Senior Robin Hood Guy

    Messages:
    2,777
    Location:
    USA
    I have checked and it would not appear to be against code everywhere, as I originally assumed. Sorry. In Illinois for example it appears to be allowed.

    But I maintain that it is dumb to have two shut-offs on a WH. If you the plumber have put a ball valve on the hot you have opened the door for human nature to injure someone.

    They possibly would not want to call a plumber when the T+P is working properly and releasing water.
    They put a cap on the T+P "I can fix this honey"...
    The heater builds up excessive pressure and pinholes a weld on the tank...
    They close both valves and know it is now time to call you to replace the heater...
    You pull up to a house with a bunch of emergency vehicles in front of it because the homeowner never turned off the gas,"It wasn't what was leaking"
    With hot open maybe they will have a chance blowing a water supply.

    Yes, there might be exceptions. From my 365+ days of plumbing experience as a fully qualified and master homeowner, I would guess that on a residential 2 heater parallel installation, installing a hot and cold on each heater might be essential. When 1 heater takes a dump, that heater can be isolated, and the other heater will work without the leaker leaking.

    But I maintain that traditionally a 1 tank residential heater will only have a cold water valve.

    A tankless might require both a cold and hot shut off with bypass valves to allow for flushing though.
    Last edited: Dec 18, 2008
  17. jar546

    jar546 In the Trades

    Messages:
    432
    Location:
    USA
    Ian,

    It is not against code to add a shut off on the hot water side and it makes it easier to service the equipment. The TPR valve is what protects the equipment. If you don't have one and all of the hot water fixtures are in the off position, it is no different than having a valve installed on the hot side and in the closed position.

    I understand your concern and appreciate your passion but you are incorrect.

    I think you need to specify the code that prohibits this, otherwise you are misleading people with false information.

    A shutoff valve is required on the cold water side per the IPC and IRC. In the IPC it can be found in 503.1 and in the IRC it is in P2903.9.2

    I have supplied you with direct references, now I ask the same from you.
  18. jar546

    jar546 In the Trades

    Messages:
    432
    Location:
    USA
    Also,

    You cannot fix stupid and keep people from injuring themselves due to their own negligence. It is bad enough that we have to have stickers on lawn mowers telling people that they are not hedge trimmers because some moron picked up a mower to trim his hedges and won a lawsuit.

    Under normal operating conditions, the valves will be in the open position.

    Again, as long as you don't have water running in the house, there is no difference between that and a closed valve on the hot side. Either way the water is restricted and pressure can build up, hence the need for a TPR valve.

    If you are stupid enough to cap the TPR, leave the gas on and turn off both valves then you don't belong in society anyway.

    If you don't like it then don't do it in your house. It is not required but it certainly is not against any nationally recognized codes.
  19. Ian Gills

    Ian Gills Senior Robin Hood Guy

    Messages:
    2,777
    Location:
    USA
    Many thanks for the clarification.

    I must have been confused on this one.

    I guess I am just be one of those weirdos who likes to see installations done as per the manufacturer's installation instructions, which never show a hot-side shut off valve for a traditional single tank installation.
    Last edited: Dec 19, 2008
  20. GabeS

    GabeS Remodel Contractor

    Messages:
    294
    Location:
    Brooklyn NY
    I'm with jar on this one. I don't see how a closed faucet or shower head is any different from a closed valve. I guess Ian is suggesting that a soldered copper elbow is a weaker connection than a valve and would burst before the tank would as opposed to a ball valve not bursting in a high pressure situation. This may or may not be correct, but I can't imagine a huge difference in strenght between the two.

    Also, I believe a bigger concern would be to have threads on the bottom a T&P extension pipe, where a unfamiliar homeowner would even have the ability to cap it. Absolutely no threads allowed on the bottom of that pipe.

    A hot water side valve would allow you to change the water heater without having to drain all the hot water lines.
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