Expansion Tank Question - also a water pressure question afterthought!

Discussion in 'Water Heater Forum, Tanks' started by Penny Weiss, Aug 8, 2014.

  1. Penny Weiss

    Penny Weiss Bless our troops!

    Jun 19, 2014
    Retired County employee - accounting
    Lompoc, California
    I have an expansion tank for my hot water heater that is installed horizontally and is unsupported (AKK!!!) The location is .. the water supply comes out of the wall above the water heater, a flex hose is connected to a T and screwed into the nipple at the top of the water heater. The expansion tank is hanging off the T.

    The water heater was dripping water today and I got a plumber in who checked it out for me and found that the leak was the rusted nipple where it screws into the water heater. He removed the expansion tank, was able to remove the nipple and replace it, putting the whole thing back together.

    Yes, I will be replacing the water heater, but I have to leave town early tomorrow, so thankfully, it's not leaking and I'll do the replacement next week upon my return. And yes, I will have him either hang the expansion tank vertically or strap it to the wall or from the ceiling. I can't believe the licensed plumber who installed it just left it sticking out. I read the forums and I get it.. And yes, I'll replace the broken shut of valve that's leading to the water heater, too.. who knew!!!

    My question: does the expansion tank just screw back on? Is there a need to check the pressure with a tire pressure gauge, or is it pre-set? When he took it off and I turned it over, just a bit of water came out.. maybe 4 ounces. I can't find instructions anywhere on it.

    I guess I have 2 questions: I have a pressure guage on the hose bib in the back yard and it has risen to 50 psi during the past 10 hours, but is sitting at about 45 psi right now. Hmm.. that's low, should I increase that at the water pressure regulator? I do get humming, not hammering from my pipes if I'm running water at low volume - maybe 55 psi would be better?

    Thanks in advance from this old lady!
  2. Reach4

    Reach4 Well-Known Member

    Sep 25, 2013
    says they come precharged to 20 PSI, and that should be increased. I had thought 60 PSI was common for new tanks, and that would be OK for most.

    Ideally that precharge would match the high water pressure under normal conditions. A little high is OK. https://terrylove.com/forums/index.php?threads/expansion-tank-air-pre-charge-pressure.3578/

    The purpose is to keep the water pressure from exceeding 80 PSI due to heat expansion. The expansion tank provides a place for the expanded water to go.
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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    You must have the water supply turned off and a hot water valve open until it stops flowing - then, you can check the precharge water pressure in the ET. If you check it before you start, that will tell you the system's water pressure (unless the precharge is WAY too high). The goal is to have the air pressure about the same as the water pressure when applied, so that the bladder is sitting at a neutral position. This also allows for maximum expansion without stressing the bladder too much. Horizontal verses vertical doesn't matter, but it should be supported, since when it does fail (they all do eventually), and fills up with water, you don't have a huge weight and lever stressing the connection.
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