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Tanklets > Expansion Tanks

Q: A number of years ago the local water company changed from an open system to a closed system when they changed out water meters, as in they added a foot valve after the meter (the meter is in the basement, due to the cold climate). I never thought anything about it till I happen to notice my 25 year old 30 gallon electric hot water heater dripping out of the TP valve into a floor sump.

A little googling suggested checking my water pressure. 25psi static, and a scary high of 125psi under the right (wrong?) conditions. So I bought a Watts PLT-12 potable water expansion tank. I'm trying to figure out how to best mount it. Will it last longer mounted inlet down or up? I just want to do this once.

A: You can put it anywhere as long as it's not right on top of the water heater. Hot water drawn into it by convection will wear out the rubber diaphragm more rapidly. Also, it's time you checked the anode in that water heater! -- Randy

Q1: Thanks for the reply. I think it's a good time to just go ahead and change the whole water heater, seeing how I've neglected it all these years. I'd hate to start changing all the parts, then have the tank fail, but I want the to fix the pressure problem before I install a new tank. I have a wall that I can mount the expansion tank on, and can set it up either inlet down or up, or sideways, just not sure which is better. Sounds like perhaps it just doesn't really matter.

A1: Hello: There are differing opinions on this. My opinion is to mount the tank above the pipe it's hooked up to. This way any debris does not collect in the tank. I'd also put a valve between the tank and pipe so air charging and any maintenance become easy. I've got heaters out there over fifty years old. Yours is old but not necessarily over the hill. No doubt you have good water, even if it's at only 25 psi. -- Larry (11/18/10)

Q: Is replacing an expansion tank for a gas hot water heater something I can do myself without calling a plumber? If so, what are the steps? The expansion tank I have now is rusted and is leaking water.

A: Most residentual expansion tanks screw in (like a light bulb). Just make sure the heater is turned off along with the water. Relieve the pressure by opening a hot side of any faucet. Follow the intructions for checking the air pressure of the bladder before screwing the new tank in. -- EJ

Q1: Thank you for your comments. Do I need to empty the water heater any (e.g., below the level of the relief valve) before I unscrew the expansion tank? Or is turning off the water enough?

A1: This depends where your tank is located. If the pipe that the tank screws into is located above the heater and you have plumbing above that then you might want to drain some water off so nothing gets wet. It really depends on how fast you are and where the tank is located. Good luck! -- EJ (10/22/06)