Where to add expansion tank?

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  #1  
Old 06-16-03, 11:57 AM
Wick
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Where to add expansion tank?

I am on a closed system, from a PRV off of city water.
Every time the water heater runs for a while our
pressure goes up to about 90 PSI, I bought a cheap
pressure gauge and thought it might have been a fluke.
But watched it go up from 55 to 95 with in a matter of
about 30 seconds. So the first time the water is run after
this it causes alot of noise in the pipes.
I have a 40 gallon gas water heater. Does it sound
like I need a expansion tank? If so where should it be
installed, hot or cold, does it attach right to the water tank?
Any advice would be appreciated.

Wick
 
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Old 06-16-03, 03:07 PM
maadi_griffin
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Old 06-16-03, 06:23 PM
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Install it near or by the inlet side of the water heater.
 
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Old 06-17-03, 09:14 AM
Wick
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Thanks.

Anyone know of a link to help with the instalation.
 
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Old 06-17-03, 11:02 AM
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What type of pipe is it at the water heater and size?
 
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Old 06-17-03, 01:14 PM
Wick
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1/2 in. Copper going to and out of the tank.
 
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Old 06-17-03, 03:37 PM
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Expansion tank has a 3/4" inlet. so you need to increase the pipe on cold side of the heater, you cut and sweat in a tee and a stub up with female adaptor on it.

Female adpt, will accept the expansion tank, 1st step is you need to know what the static pressure is on the house, with a pressure guage, before you connect and look at the pressure, turn the hose bibb on for a few seconds, turn it off, install the pressure guage, read the guage, write it down so you don't forget it.

Now in the tank is a bladder, you have to pressurize the expansion tank to just above the pressure you noted on the guage, I like to pump them to +5 higher then the static pressure, of course it does not have to be at +5 higher, you can set it even higher then that, just as long as it is higher then the house pressure. and don't pump it up to 150PSI, thats when the T&P valve will pop-off on your water heater. reason is if you don't and the pressure in the tank is less then the house pressure, guess what? Yep you will fill the tank up as soon as you get it installed and you turn the water on.

Thats it,
 
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Old 06-17-03, 03:59 PM
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You should have the thermal tank regardless but I would think you might have a bad PRV as well... Thermal expansion doesn't usually happen over a 30 second period to that degree... A PRV that is going bad will cause quick erratic movement in pressure that way... Especially if the county has recently done work and caused the PRV to get filled up with trash and debris...
 
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Old 06-17-03, 04:31 PM
Wick
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This is my first house and just moved in a couple months
ago. So I don't have much experience with plumbing.

The house is 25 years old, so I have no idea
of the age of the PRV. Would the water company have
done anything to it since it is attached right to
the meter? There was a new gauge put on the meter
when I moved in. The pressure stays very steady,
it only raises when the hot water tank runs for a while.
Maybe I should just replace the PRV also, they are around
$30 right?

thanks again for all the advice.
 
  #10  
Old 06-23-03, 12:11 PM
Wick
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Thanks plumber2000 for all the help. I put the tank in
this weekend. I was a little nervous about solderind
( have not done it since high school shop class which
has been almost 10 years). Everything went fine, no
leaks. The tank is 10+ the house pressure. I was
concerned about the accuracy of the tire gauge I was
using compared to the water pressure gauge, so I wanted
to go over 5+.

I was not sure if a soldered joint could hold the weight
of the tank? So I got a Tee with the a threaded
female end. Just courious, how much load is to much
or a soldered joint, hanging something verticaly from it?
 
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Old 06-23-03, 12:21 PM
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Should be fine, as long as the pipe comming out of the wall felt good and secure it should hold with no problems.

Glad you solved the problem.
 
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