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Thread: Leaking Water Heater From Relief Valve

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    DIY Junior Member jjrr007's Avatar
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    Default Leaking Water Heater From Relief Valve

    We have an electric water heater that's connected to the sewer line (at the relief valve). It started leaking from the relief valve. I wanted to please ask:

    * Is it a good idea to have the relief valve connected to the sewer line in case it leaks? In case it leaks from the relief valve, it's hard to tell. I am not sure if we should continue to have the relief valve connected to the sewer line.

    * if the relief valve is leaking water, should I just replace the relief valve? I think it's a matter of just draining the tank and removing/installing with pipe thread. Is there anything else I should do know to relieve pressure before replacing the relief valve.

    * If our electric water heater leaks from the relief valve, can this cause our electric bill to increase?

    I appreciate your time and views. Thanks!
    Last edited by jjrr007; 02-12-2012 at 03:02 PM. Reason: clarity

  2. #2
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    No the relief line should not connect to the sewer.

    You can replace the relief valve.

    You need to check the operation of the heater to make sure its working properly.

    You need to check your water pressure.

    You need to check your thermal expansion protection and make sure its providing protection.

    NEVER cap or plug a relief valve,under certain conditions the water heater can explode like a bomb. LITERALLY.
    Last edited by Hackney plumbing; 02-12-2012 at 03:06 PM.

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    DIY Junior Member jjrr007's Avatar
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    Thanks. how do i check the thermal expansion protection?

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    Retired Defense Industry Engineer jadnashua's Avatar
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    That valve on the WH is called a temperature and pressure safety valve (T&P). It is designed to keep the WH from blowing up if either it gets too hot, or the pressure gets too high. It should be easy for you to tell if it is too hot.

    When you heat water, it expands. Since the piping in the house is relatively inelastic, when trying to increase volume, the pressure starts to go up radically (think pushing a boulder...it doesn't move, but you strain a muscle pushing). Something has to give, and that's the T&P valve. It could be weak and leaking at a lower pressure than designed, but it's more likely that the pressure is opening it.

    If you have a closed system (this means there's either a check valve or something like a pressure reduction valve (PRV) in the house), then that blocks that expanding water from just pushing back out to the street, keeping things releatively constant in pressure. The solution to this is to use an expansion tank. This is commonly a bladder tank...water on one side, air on the other. The pressure goes up, it collapses the bladder, compressing the air, and expanding the volume available for the water. The bladder eventually fails. If you have an expansion tank, it probably needs to be replaced. This is generally pretty easy. Turn the water off, open a faucet, unscrew the old one (it will be heavy as it's partially full of water), screw on a new one. Prior to that, you should add air based on your normal house's water pressure. This is so that under normal conditions, the bladder's air pressure essentially matches the water pressure, so there's room for it to expand when the water gets heated. The tank has a fitting on it (a Schrader valve) just like a bicycle or auto tire, you can use a hand pump and tire pressure gauge to preset it to the needed value before installing. The only other thing you'd need is either some teflon tape or pipe dope to seal the threaded connection. Most people won't need a wrench to remove or install the new one since the tank is plenty big enough around to get enough leverage.

    If you have an expansion tank, and if you don't, you may need one, if you knock on it, it should sound sort of like a bell if it is mostly full of air. If it has failed, it will sound more like a thunk than a ping and will feel heavy.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    1) You need to disconnect the relief pipe from the sewer and pipe it to a suitable location.

    2) Check the operation of the thermostats and test the elements. A grounded element or loose wires can cause a water heater to overheat.

    3) Replace the relief valve.

    4) At an outside hose bibb attach a pressure gauge and open the valve. Insure there are no drips. Insure the water pressure does not exceed 80 psi.


    5) Take a meter reading at the water meter and write the numbers down and check to make sure there are no leaks in the system. Turn off all automatic appliances like ice makers and other automatic appurtenances are turned off before taking this reading.

    6) Draw 30% of your tanks volume in hot water off the tank at a hot water faucet. Shut the valve and do not use any water. Insure that the water heater is in operation and is heating the water.

    7) Go out to the gauage and baby sit it. If the pessure exceeds 80 psi your thermal expansion protection is not operating properly.

    8) Go back out to the water meter and insure NO water has been used and the meter is showing the smae reading as before the test.

    9) report back your finding to the forum.

    10) send a check payable to......LOL just kidding.

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    DIY Junior Member jjrr007's Avatar
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    Thanks for the replies. This water heater is in an apartment complex. There isn't a hose bib that i can connect to for this apartment. I don't see an expansion tank as this place was built around the 70s. I can do the first three steps mentioned, but where do I take the readings from for the pressure gauge. Also, I have heard that if your water heater is more than 10 years old, it may be best to replace it (use an expansion tank as well). do you agree?

    It may be easier to install a pressure reducing valve. I realize it's hard to tell what to do without more facts, but I can see if the pressure is high. Just don't know where to test it for this apartment unit.

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    Quote Originally Posted by jjrr007 View Post
    Thanks for the replies. This water heater is in an apartment complex. There isn't a hose bib that i can connect to for this apartment. I don't see an expansion tank as this place was built around the 70s. I can do the first three steps mentioned, but where do I take the readings from for the pressure gauge. Also, I have heard that if your water heater is more than 10 years old, it may be best to replace it (use an expansion tank as well). do you agree?

    It may be easier to install a pressure reducing valve. I realize it's hard to tell what to do without more facts, but I can see if the pressure is high. Just don't know where to test it for this apartment unit.
    Do you own the apartment? Do you have a separate water meter for your apartment?

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    DIY Junior Member jjrr007's Avatar
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    I am the "maintenance man" for the apartment complex. The building has it's own meter for many apartments. Two in fact to ensure enough pressure through the complex.
    Last edited by jjrr007; 02-12-2012 at 05:26 PM.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    You may not have needed an expansion tank previously, but the utilities have been retrofitting check valves, and what worked before, may no longer work...so, you may need an expasnion tank. You can use the drain valve of the WH, or connect to a washing machine connection, or anywhere there's that type of fitting, or, pick up adapters, unscrew an aerator for a faucet and screw one in there. Any of the big box stores sell them about abou t$10 and try to get one with a second tattle-tale hand to show peak pressure...leave it attached say for 24 hours. If you have an expansion problem and a closed system, you'll see the pressure peak to about 150psi, where the T&P will weep to relieve the pressure. An expansion tank would accept that water, and the pressure would stay pretty constant.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Quote Originally Posted by jadnashua View Post
    You may not have needed an expansion tank previously, but the utilities have been retrofitting check valves, and what worked before, may no longer work...so, you may need an expasnion tank. You can use the drain valve of the WH, or connect to a washing machine connection, or anywhere there's that type of fitting, or, pick up adapters, unscrew an aerator for a faucet and screw one in there. Any of the big box stores sell them about abou t$10 and try to get one with a second tattle-tale hand to show peak pressure...leave it attached say for 24 hours. If you have an expansion problem and a closed system, you'll see the pressure peak to about 150psi, where the T&P will weep to relieve the pressure. An expansion tank would accept that water, and the pressure would stay pretty constant.
    Problem with a peak pressure gauge is quick closing valves make them spike. Try it.

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    I do not know how many units we are talking about in this apartment complex but the chances of the system being truly closed in not likely. Especially if this is an active complex. Apartment complexes are notorious for having dripping faucets and running toilets because the tennants usually do not pay a water bill based on their actual use.

    Very little water needs to be relieved from a system for you not to see a rise in pressure. But all that said it could be thermal expansion but adding a tank to that one apartment is not going to do any good. You would need to add the load up and install one large tank or install individual tanks or protection in each apartment.

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    Quote Originally Posted by jjrr007 View Post
    Thanks for the replies. This water heater is in an apartment complex. There isn't a hose bib that i can connect to for this apartment. I don't see an expansion tank as this place was built around the 70s. I can do the first three steps mentioned, but where do I take the readings from for the pressure gauge. Also, I have heard that if your water heater is more than 10 years old, it may be best to replace it (use an expansion tank as well). do you agree?

    It may be easier to install a pressure reducing valve. I realize it's hard to tell what to do without more facts, but I can see if the pressure is high. Just don't know where to test it for this apartment unit.
    If you don't have a hose bib there are other options. The most obvious is to put the gauge on the water heater drain valve (open the valve obviously.) However, since many of these are plastic be extremely careful...I had one leaking once and tried to tighten the packing gland, as soon as I gently touched it with a small wrench it sheared off blasting me with hot water! Turns out the leak was at the threads (non-obvious as it was a fouled mess at the time) because the plastic was weak and cracking.

    If you can find the right fittings you could even take the pressure measurement from a faucet tap.

    PRV's won't fix a thermal expansion issue. They will fix a high supply pressure issue.

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