Thermal Expansion Tank


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Old 08-29-06, 07:47 AM
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Thermal Expansion Tank

When my water heater was being replaced, the installer offered to install a thermal expansion tank for $129. He said it would eliminate the noisy pipes that we have due to high water pressure.

I declined because:
1. Our pipes have never made any noise.
2. In 20 years, the house has never had a thermal expansion tank .
3. We have a pressure reducing valve on the main water line coming into the house.

Did I make the right decision here?
 
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Old 08-29-06, 03:31 PM
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If you bought the Ruud (Rheem) heater and have T&P valve leaking issue, dont EVEN call if you opted to not get the thermal expansion tank. :-P

Not to say it will happen...

Well my old heater never went out in my attic.
Well my old heater never leaked from the T&P valve.
Well my old heater always gave me plenty of hot water.
Well my old heater lasted 20 years.

... but this isnt your old heater.
 
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Old 08-30-06, 04:50 AM
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Hello XS6DFG0.

Did you make the right decision? Answer. Yes.

If the water heater is not connected to a boiler, it is free standing, has a Pressure/Temperature releif valve, the main inlet water line to the entire house has a water pressure control valve and there isn't any exisiting/current problems, no expansion tank should be needed.

In my opinion and based upon my vast number of years of experiences as an appliance serivce tech, no expansion tank should be needed for a non interconnected free standing gas water heater.

Check back on your question several more times. Other members and the plumbing professionals posting replies in this forum topic may offer you additional advice.

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Old 08-30-06, 06:12 AM
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Thanks for the replies.

BTW, I went with the Bradford White instead of the Ruud.
 
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Old 08-30-06, 02:55 PM
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Expansion Tank

My understanding that an expansion tank is needed if a pressure reducing valve or back flow or check valve is located between the supply and hot water heater.

Without one there is nothing to take up the water expansion--usually the pressure relief valve takes over...
 
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Old 08-31-06, 07:48 AM
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I guess if the T&P valve ever vents, I'll add an expansion tank.

Am I correct in assuming that larger tanks are capable of producing more pressure? We only have a 40 gallon tank.
 
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Old 09-03-06, 11:33 PM
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Since you stated in your original post that you have a PRV on your incoming water line the answer is YES, you do need an expansion tank. Failure to install one could void the warranty on the new heater.

The volume (size) of the water heater has no bearing on how much pressure it is capable of producing. Point in fact, the heater cannot produce ANY pressure, it is the fact that you are adding heat to a closed system (the heater and the attached piping) that causes the pressure to rise.
 
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Old 09-13-06, 10:15 PM
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I agree with Furd. You can buy a cheap pressure gauge and screw it onto the water heater drain, open the drain, and watch what happens after someone takes a shower.
 
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Old 09-14-06, 08:46 AM
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Originally Posted by steve_gro
I agree with Furd. You can buy a cheap pressure gauge and screw it onto the water heater drain, open the drain, and watch what happens after someone takes a shower.
If I do this, how much pressure is too much?
 
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Old 09-15-06, 12:19 AM
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My local codes require a PRV at 80 PSI The relief valve on the water heater is probably set at 150 PSI. I would start thinking about an expansion tank based on the pressure increase after someone takes a shower, or if the pressure approached 100 PSI. That is, if the water heater heats a tank of water & it only increased a few PSI, you could leave it, but I suspect that it will creep up a little more than that. Check the water heaters mfg's website, or call them to see what they have to say, esp regarding the warrantee.

If I install a water heater and there's a PRV, I normally recommend an expansion tank; they aren't expensive, or much trouble to install.
 
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Old 11-13-08, 12:19 PM
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Do I need a expansion tank?

I have a PRV set 80psi and it is leaking should I install a expansion tank.
 
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Old 11-13-08, 12:30 PM
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Arpan...do you mean a "pressure regulating valve" (PRV) or a WH pressure relief valve (commonly called a T&P valve).

If I'm right, 80 psi is pretty high for a PRV, 60 is more common as I understand.

Anyway, if your PRV is leaking, it may need rebuilding or replacement.
 
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Old 05-01-13, 07:04 PM
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expansion control

most if not all your manufacturers require the expansion control of some sort, and since it is unpredictable , expansion tanks are the best options.
most local and plumbing codes do require a means of expansion control.....look up or call your local plumbing codes enforcement.
in our area it is done on all water heaters esp. gas:No Beer 4U:
 
 

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