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Discussion Starter #1
If you have no check valve on your incoming water line, is there any point or benefit to having an expansion tank?

I am planning to do some plumbing stuff on my house soon, and I was planning to install an expansion tank because I thought it would be a good thing.

I then started thinking if the water already has a place to expand (backwards into the city's water tower or whatever), will having my own expansion tank accomplish anything?
 

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Discussion Starter #3 (Edited)
Well yeah, this would be for the water heater. I should have said that. I am planning to change out it's anode rod, as well as to do some other stuff and I thought while I have the water off it might be a good time to install an expansion tank.

I was thinking that the expansion tank might help my faucets last longer before developing drips, but then I got to thinking that since my home doesn't have a check valve between it and the city water supply there probably really isn't much of a point.

I already picked up the expansion tank. Should I install it or bring it back to the store?

If anyone can think of any benefit that it might provide I will install it. Otherwise I won't bother. Thanks.
 

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Their primary use is exactly as you understand...to prevent pressure buidup of hot water as it expands.......

BUT, I wonder if it has a monor affect on water hammer throughout your system....never thought about that till your post.

I use arresters at point of use. (If you never had a hammer problem, I would not bother installing it.
 

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Expansion tanks on hot water are for closed loop systems, I don't believe that a ET would be of any use for water hammer, as MTN stated there are arrestors for that purpose.
 

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1. The expansion tank might be required under your city's code.
2. The water company might install a check valve or a new meter with a check valve the next time the meter is changed out as normal maintenance.

The expansion tank does not fully suppress water hammer when it is far from the point where a valve or faucet may be turned off rapidly to cause the water hammer. It is the entire column or slug of water moving in the pipe that generates the shock wave when forced to come to a stop when the valve is turned off. A water hammer arrestor downstream of or in a different branch of the plumbing from the valve being turned off will also have little effect.
 
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Good point of ALLAN that your city/county might require it.... never thought of that as I've never incurred that.



( As I think back, I installed a water heater in a property that had a gravity fed high water pressure with no PRV. It was about 90 PSI and I told the customer that he probably shoulld have a PRV installed.

The WH had a expansion tank so I left it installed and just plumbed in the wH as is. He said he had no problems/leaks/appliance issues or hammer.BUT I doubt that the expansion tank had anything to do with that. He was a cheap SOB....(sweet ole boy for the censors)
 

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If you do not have a check valve on the water to your house, or a pressure reducing valve you do not need an expansion tank on the hot water tank. But do call your water supplier to make sure you do not have a check valve built on the meter set.
 
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