Water expansion tank question

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  #1  
Old 07-16-07, 07:56 PM
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Water expansion tank question

A plumber came today to fix something, and he told me that I need to replace the water heater ST-5 expansion tank (I think it is 2 gallon size), since there is no air in there any more. The house was built in 2001. A friend of mine said he can do it for me. Questions:

1) What brand is a good brand to buy? I went to internet, it seems to point to Amtrol THERM-X-TROL ST-5 Expansion Tank, Model Number - ST-5.

2) Any plumbing supply company you recommend? I saw on ebay sell this brand for $32. Also at PlumberSurplus.com, sell it for $49

3) Do I need to buy any other accessories, when this tank is to be replaced? Such as connector or valve? What size? and what brand?

4) Anything else that I need to pay attention to?

Thanks for your help!!
 
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Old 07-16-07, 08:27 PM
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Maybe just need to recharge with air and not replace. Was there water on the valve side(bottom) of the tank.
 
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Old 07-16-07, 09:03 PM
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The plumber said in the tank, it should have air as well as water. But the tank only contains water now. He said a brand new tank comes in with air inside only. Once it is in use, then water will start to force into the tank. But there is no leaking from the expansion tank. He said if I do not replace it, it may cause damage to the hot water heater and start to leak.
 
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Old 07-17-07, 03:52 AM
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Perhaps an overview of a tanks construction.

The tank has a bladder, basically a sheet of rubber, that splits the tank in half. One side is connected to your water line, and will eventually fill with water, that's what it's suppose to do. The other side however is pressurized air, which is typically adjusted using a tire valve type connection (hidden under a plastic cap). The pressurized air side should never have water in it, if it does that means the bladder leaks and the tank is no longer doing what it is suppose to do.

An easy way to check for this is to simply let the air out of the air side (through the tire valve). If you get more than a few drops of water, the tank is leaking and needs to be replaced. If all you get is air, then repressurize it to what your normal static water pressure is. If you have it regulated to 50 PSI, then pressurize the tank to 50 PSI, this will place the internal bladder in a neutral position, ready to absorb temperature changes.

The tanks themselves are fairly cheap (available at any home center) and can be replaced simply by turning off the water supply, unscrewing the old tank, screwing the new tank in place and then adjusting the air pressure as described above.
 
 

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