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Author:
drsusan32 (CA)
Hi,
I have learned here about pressure regulator and ball valve for water supply to house, but I really don't know the purpose of a pressure expansion tank after these near a water heater. I was told something like when water heats up it makes water pressure go up a bit which can over time damage water pipes again. Is this true and is this pressure expansion tank going to be a benefit? Why have no others talked about it when bidding our repipe job?
Thanks for any insights on this and for listening.
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Author:
hj (AZ)
A check valve or pressure regulating valve, creates a closed system and when water, being highly incompressible, is heated it expands and causes the pressure in the system to increase, possibly to 150 psi when the heater's relief valve will prevent further increase. An expansion tank adds a "bubble" of air into the system, and since air is highly compressible the water expansion just causes the air to rise in pressure, but no where near as fast or high as water by itself. They do not mention it, because they feel that since plumbing fixtures ARE designed for a 150 max working pressure, the heater's valve will limit that and as soon as any water is used the excess pressure is drained off.
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Author:
drsusan32 (CA)
Hi and thanks for your explanation. Do you think it would be of any benefit to have a pressure expansion tank installed near the water heater on a copper repipe job for house?
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Author:
hj (AZ)
it makes no difference where it is installed as long as there are no valves installed that could isolate it from the system.
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Author:
drsusan32 (CA)
HI, and one final note, we have a really old water heater that works fine. Would that be any reason to be installing a pressure expansion tank near it?
Thanks for listening and any comments.
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Author:
RRWA (WA)
If you have a closed system, you need to install an expansion tank.
You first need to determine if you have a closed system.
This can be done by comparing the water pressure before/after.
1. Take reading 1.
2. Use significant hot water(fill the bathtub) and then wait for the water heater to recover(30 minutes). Do not use any water during this time.
3. Take reading 2.
I would not repipe a house without addressing this concern. It would be foolish to spend so much money while ignoring a relatively simple detail.
Why do plumbers not mention this? It is likely beyond the scope of a repipe and would add extra cost which may decrease their likelihood of winning the bid due to price focused customers.
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Author:
drsusan32 (CA)
HI and thank you for that very detailed well written explanation. Yes, I think after the pressure regulator valve will be installed, we will have a closed system and will need that pressure expansion tank. The plumber who told us we did actually had it in his bid. But he was the only plumber who even talked about needing it. I liked him the best as he seems knowledgeable and comes with his crew to do the job. So finally we have made a decision and can get started on this huge repair very soon.
Thanks again for all the good help learning about piping!
Happy Thanksgiving!
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Author:
hj (AZ)
IF you need an expansion tank then the age of the heater has nothing to do with whether to install one or not. IF your system does NOT need one, then there is absolutely no reason to install one.
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