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Thread: Expansion Tanks: where/how do they fail?

  1. #1

    Default Expansion Tanks: where/how do they fail?

    Hi guys:

    I'm finishing the basement and along with that project, I finally got around to changing out the WH which I've had "issues" with over the years. The old one was junk from day 90 and now about at the end of it's 9 year warranty anyway. So instead of repairing it, I put in a new one, relocated it and added a second WH in series while I was at it for some needed extra HW capacity.

    The new heaters were plumbed for H2O and functional, I was going to pipe the T&P valves the next day. Turned out to be a good thing I had to wait on that piping because I discovered the T&P's were "relieving" (via the 2-3 gallons in my basement floor the next AM). Had I only installed one heater, I'd have thought it was leaking, but as both drain pans on both new heaters were full, I knew I had a simultaneous discharge on both T&P valves (first of 2 new WH's is electric and not wired yet). So, I figured I had to have something up with pressure. A $10 Watts guage confirmed it, I found my PRV must be bad as the static pressure in the house was 120-130, peaking to 150+ . Thus the T&P relief. (City water is at ~120-130)

    My expectation is that this has been going on for possibly years and I didn't know becasue the T&P was plumbed to a drain, and I would have never known if was relieving regularly. This might explain a not to distant failure of some poly lines in the old fridge (now replaced) and a subsequent poly line failure on the dishwasher, too

    A little quick research, and I found I was missing the integral component - the expansion tank. While I did the repair and new WH install myself, the original design and install including the PRV was done by a "pro". So I don't get credit for the original miss on the no-expansion tank.

    Of course I have replaced the PRV. Mine is a Watts with unions on both ends so the $35 at Home Depot for a new one and 10 minutes to change was better for me that to try to see what was wrong with the old one. Biggest problem I have right now is the wife is ill with the 50psi shower, she has become accustomed to the pressure washer we/she had last week .

    Now to the expansion tank. I have a variety of places I can locate it, none are good. I've looked at every brand out there I think. I can only find one that comes with any warranty. It was a hair more expensive, mostly due to the special order, so for peace of mind, I have it on the way (State/AO Smith). They are probably all made at the same plant in China, but at least State was banking on it not failing for 5 years.

    My question to you experienced guys is this; when these little expansion tanks fail, where do they fail? When I say fail, I don't mean internally with a bladder leak, I mean externally or anyplace that would cause a water leak. All my install locations are bad for leaks and I don't have any practical way (place) to put a drain pan under the thing. I envision (have nightmares about) a split expansion tank seam with water spewing out the side (picture - old submarine war movie). Do they fail like that, or just start to seep and drip?

    For any that you have seen leak, where and how do they leak? How reliable are they (leak wise)?

    And, for my wife's sake, I figured I'd turn the PRV "up" to maybe 75 psi (and charge the expansion tank appropriately). Any problems with that plan?

    Thanks!
    Scott
    Last edited by shorton; 02-12-2009 at 12:37 PM. Reason: clarity

  2. #2
    Master Plumber master plumber mark's Avatar
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    Talking they rarely leak

    on rare occasion I have seen an expansion tank leak or rust a hole
    out the side of it..

    it can happen , but only a few times in my experience...

    when they do leak it usually can be catastropic,
    pissing water everywhere


    I honestly dont care for them but I have one in my own home... its just something else that can go wrong. and over time they can get very heavy with water..

    no one maintains them, no one checks the air pressure ,
    and no one wants me to come back out
    and pay me $150 to change it out 5 years from now either...



    its best to install the expansion tank over the
    top of the water heater, and mount it so it wont wobble or
    topple over some day... I have actually used some heavy guage
    copper wire and secured it to the overhead rafters...


    if you were to just hang it in mid air and
    it breaks off the 3/4 copper pipe due to
    a weight issue 5 years from now,
    you are soooooo very deeply , totally screwed......

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    My understanding (and limited experience) is that the bladder is the first thing to go. This does not usually cause an external leak, but you would notice the T&P valve releasing the excess pressure because the tank is no longer functioning. Depending on how you installed, it, since it could be full of water, you could spill some in the replacement process. I think it is a good idea to (after supporting it well) hang it and have a shutoff valve on the t going to the tank so you don't even need to drain anything if you keep the tank upright when removing it. Much harder if it is on its side! You could have a few gallons drain out while unscrewing it.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #4
    Master Plumber master plumber mark's Avatar
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    Talking I totally agree

    yes that is a good idea to
    install a shut off valve to it so it can be easily changed

    most people dont want to spend the extra 6 bucks for that either (tight-wads)

    the bladder goes first, then the water starts to attack
    the other side of the tank liner.....

    then the the weight of 4 gallons of extra
    water becomes an issue
    if you dont have it secured well....


  5. #5
    Illinois Licensed Plumber SewerRatz's Avatar
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    Quote Originally Posted by jadnashua View Post
    My understanding (and limited experience) is that the bladder is the first thing to go. This does not usually cause an external leak, but you would notice the T&P valve releasing the excess pressure because the tank is no longer functioning. Depending on how you installed, it, since it could be full of water, you could spill some in the replacement process. I think it is a good idea to (after supporting it well) hang it and have a shutoff valve on the t going to the tank so you don't even need to drain anything if you keep the tank upright when removing it. Much harder if it is on its side! You could have a few gallons drain out while unscrewing it.
    Sorry per code that is not allowed. Below is from Illinois Plumbing Code book.

    A properly sized and approved expansion tank shall be located on the water heater's cold water supply with no shut-off valve between the heater and expansion tank.

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    In the Trades Gary Swart's Avatar
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    I believe the Jim was saying the valve would be between the tee in the supply line and the expansion tank, not the water heater tank. This will allow the expansion tank to be shut off and changed without shutting the water to the heater off too.

  7. #7
    Illinois Licensed Plumber SewerRatz's Avatar
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    Quote Originally Posted by Gary Swart View Post
    I believe the Jim was saying the valve would be between the tee in the supply line and the expansion tank, not the water heater tank. This will allow the expansion tank to be shut off and changed without shutting the water to the heater off too.
    Huh? What the code is saying you are not allowed to put a shut of valve between the expansion tank and the heater. So lets just say you used an IPS shut of valve and installed it right on the expansion tank then to the tee, the valve is still between the expansion tank and the water heater.

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    Master Plumber master plumber mark's Avatar
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    Talking code is different everywhere

    Sewer Ratz....the code is different everywhere

    and besides, no body in Illinois knows what the hell they are doing...

    you guys elected Obama to the congress
    didnt you?? LOL

  9. #9
    Illinois Licensed Plumber SewerRatz's Avatar
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    Oba-who? No idea who he is.

  10. #10
    Retired Defense Industry Engineer jadnashua's Avatar
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    Putting a valve there is like not having a tank at all, so, if the tank has failed, it isn't doing anything. But, you got to do what you got to do.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  11. #11
    Plunger/TurdPuncher kingsotall's Avatar
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    Hit the road two wong fu


  12. #12

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    Thanks guys, don't care what the code says, I'm putting a valve in between it and the main line. To make it easy to change, and almost trivial to do a 2 year inspection on. Worst case it's not "there", and it's not there now either. Anyway, I know what it is and won't turn it off.

    Problem about knowing when it's bladder goes bad is I can't tell when the T&P's hit, they go down the drain.

    Guess I'll just add it to my list to check with the smoke detectors twice a year I guess.

    Or maybe install it with a washer hose, and hang it from a scale, or plumb it to the floor and let it sit on one; then I can see when it's "heavy" and know something's up . Build in an alarm - something to patent... naaa no time.

  13. #13
    Illinois Licensed Plumber SewerRatz's Avatar
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    You have a shut off valve to the cold water supply, why add one between the expansion tank and the heater? Here is the best advice anyone can give you if you choose to follow it or not is up to you. Call you local plumbing inspector, ask him what the code is regarding the installation of an expansion tank. You want to follow your local codes. If and when you go to sell your home, a home inspector will write up any violations they find and they need to be corrected.

    As a plumber here in Illinois, when I give advice, I must give it according to what the code is here in Illinois. So it is always best to check with your local code enforcment officers to find out what is allowed in your state, county, and city.

  14. #14
    Moderator & Master Plumber hj's Avatar
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    Default ?

    I believe the Jim was saying the valve would be between the tee in the supply line and the expansion tank, not the water heater tank

    Unless the water is going through the Twilight Zone, a valve between the tee and the tank IS THE SAME as a valve between the tank and the heater. The only way a valve between the tee and the tank will help with periodic inspections is if you REMOVE THE TANK. Otherwise the pressure will remain the same regardless of how you test it. Without the valve you can close the heater's valve, open a faucet to relieve the pressure and then use an air gauge to see what the air charge is. The tank failures I have seen have been where the connection is welded to the tank.

  15. #15

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    Thanks guys. Jim, I do understand. And I understand the codes and advise perspective. I do appreciate the advise, but for this one I choose to add the $8 valve for future repair convenience. The reason I'd put a valve at the tank is this:

    1) The best one I can find has a 6 year warranty. That tells me they really don't expect these to last too long. A proactive replacement is probably prudent if flooding is a concern. As a minimum a proactive through check including disconnect.

    2) With a valve, I can isolate it to change it, or periodically inspect it without having to shut down the whole house, or make a mess. $8 valve and no-headache, no plumbing required to check. If the valve is immediately before the tank, the only water I'll get out of it is the drop in the line between the valve and the expansion tank (depressurize house before turning off expansion tank valve).

    3) In the event of a tank leak, I can quickly isolate it while I go get a replacement. The house has made it for 8 years without one, it can make it 30 minutes while I go get a replacement even if I have to turn off the WH.

    I do understand the ramifications of not having it there (or turning it off with a valve). As for inspections on home sale, I'll install a F/M threaded connection before the valve. If someone complains, it will be easy enough to remove the offending valve and screw the tank on in it's place without breaking out the torch.

    My home has enough complicated systems already, if I ever did sell it, it will need an owners manual anyway. I'll add that to the manual .

    As for my original question/concern, planning for it's failure, I can't (don't want to) install the expansion tank in the water heater and equipment room. This due to the concern of failure and flooding (mid-point of finished basement, no floor drain). I can install where it comes into the house in an unfinished basement room where flooding isn't as big a concern. But that's 10' in the air overhead. I can plumb a line down to the floor where it could sit at or just above floor height, maybe even poke a hole in a wall and let it sit under a utility sink in my garage where flooding would be a minimal concern.

    And, I was half kidding above, but if I connected it from the copper with a good quality hose (e.g. water heater hose) and had it lying on it's side in the floor, it would be a simple matter to "feel" it and see if it had filled with water. Valve or not. No?

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