Expansion tank

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  #1  
Old 09-04-11, 04:32 PM
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Expansion tank

I was hoping someone could recommend a residential expansion tank for my home. I have a 40 gal hot electric water heater. Mainly I'm looking for Brand/type, what size (2 bath home), and Install location (Should it be on the hot or cold pipe and how close to the hot water tank)

When I replaced the PRV a year ago I brought the pressure down quite a bit because when someone used a lot of hot water the system would build pressure and the release on the tank would leak a half liter or so of water.

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Old 09-04-11, 06:01 PM
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The expansion tank is installed in the cold water feed to the water heater between the water heater shut-off valve and the heater itself. The size is determined by the size of the water heater and the maximum temperature difference. I'm going to go out on a limb and state that for your water heater the smallest available expansion tank will be sufficient.

Be certain that you get an expansion tank rated for use with potable water and not an expansion tank for a space heating system. You will need to adjust the air cushion to the same as the nominal water pressure supplied to the house.
 
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Old 09-05-11, 10:52 AM
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Cool thanks for the reply. Looks like I'm headed to HD today.

A couple more things. I've also got one of those valves (not sure what it's called) that is supposed to let air in the water line in case of pressure drop from the city so the tank doesn't implode. The guy at HD said I should have one. I'm going to install them both at the same time. Right now I've got cold water then shut off then expansion tank. Does it matter where that valve goes on the cold water pipe?

When you say adjust the expansion tank to house supply are you talking city pressure which is about 130psi here or house pressure which I'm going to set about 75?

Thanks!
 
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Old 09-05-11, 11:10 AM
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Hi,

I've also got one of those valves (not sure what it's called) that is supposed to let air in the water line in case of pressure drop from the city so the tank doesn't implode.
Are you talking about a vacuum breaker or a valve with a bleeder screw on the side?

Right now I've got cold water then shut off then expansion tank. Does it matter where that valve goes on the cold water pipe?
Yes you want the valve first then the exp tank. This way if the valve is turned off the HWH will still be protected by the exp tank.

When you say adjust the expansion tank to house supply are you talking city pressure which is about 130psi here or house pressure which I'm going to set about 75?
You would set it for your house pressure. 75 psi????? Thats a bit high. You should adjust the PRV to say 55-60 psi.

80 psi is the max in most codes I know. With 75 psi and thermal expansion your psi will be well over that. Puts additional strain on the HWH and plumbing joints.

Then yes the tanks come pre charged at 40 psi I believe. You would set the pressure in the tank to what your home pressure is. Do this before you install the tank.

Mike NJ
 
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Old 09-05-11, 03:18 PM
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Aha! Yes it is a vacuum breaker.

My house it at 55 right now and the shower pressure is not what I'd like it to be..... I've replaced the bath with expensive American standard hardware. The house is 100% copper no pex. I think part of the issue might be is that the whole house is 1/2 inch even though the city feed is 3/4 they went straight to 1/2 after the prv. It was working great until the hot water tank blew because I was at city pressure. The PRV and tank had to be replaced. This is the part of the reason I'm going down this road is so I can safely increase the pressure. Right now after a shower when the water heats back up you get a big burst of pressure and if the prv is set any higher the tank relive leaks. Maybe I'll try 65 and see if that is enough.

Thanks!
 
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Old 09-05-11, 03:35 PM
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With 1/2 pipe you should not experience low flow unless you are using multple fixtures.

You have a vacuum breaker because your HWH is on a elevated/upper floor as far as my install experience is with them. Not because of a chance of implosion...LOL. As far as I know they are not needed otherwise.

The PRV valve will not let water back into the city system if the city side loses pressure.

You sould get a gauge with a hose bib adapter. Hook it to a outside faucet or the drain on your water heater. This way you can monitor the pressure fluctuations. Once you see a pattern then you van increase the PRV valve in small increments. Its easy to overshoot.

Mike NJ
 
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Old 09-06-11, 05:28 PM
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Originally Posted by lawrosa View Post

You sould get a gauge with a hose bib adapter. Hook it to a outside faucet or the drain on your water heater. This way you can monitor the pressure fluctuations. Once you see a pattern then you van increase the PRV valve in small increments. Its easy to overshoot.

Mike NJ

Yes I've done this. I'm at max right now. I played with it for several days with the gauge attached and found 55 to be max "regular" pressure. Any higher and after a shower the hot water tank expansion causes the pressure relief to leak (Also the gauge is maxed at that point)

Thanks for all the help. I will report back once the expansion tank is in.
 
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