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Old 05-13-2013, 12:13 PM   #1
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expansion tanks and pvc


On a ranch pvc pipe is used to supply water underground to the main home and a nearby (100 feet) field bathroom. Inside the house and field bathroom I use pex. The pvc is only used underground outside.

The field bathroom has a 20 gallon water heater and the pressure reduction valve is letting out water occasionally. If I install an expansion tank into the main house will that alleviate pressure for both the main house water system and the field bathroom? The two are 100 feet apart and connected underground with pvc.

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Old 05-13-2013, 12:37 PM   #2
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If I understand correctly, I think you mean The TPR valve (temperature/pressure/relief) on the water heater is leaking water.

Do you (your house) or your detached house have any PRV (pressure reduction valve) .

First... TPR valves do loose their spring tension and will release early if very old sometimes. If yours is very old, you might just want to replace it ...$10.

I ask about your PRV valves (or absense ther of) because if you need an expansion tank, it matters where you place them relative to the PRV's ... which is really your question.

The PRV is an inline sorta (coke bottle size on its side do-hickey) often right near your service entrance (and meter if its an indoor meter). It will be brassy looking and have a small nut/screw on one end.

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Old 05-13-2013, 12:53 PM   #3
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If I understand correctly, I think you mean The TPR valve (temperature/pressure/relief) on the water heater is leaking water.
No I don't mean leaking water. It is doing it's job. When pressure rises above 100 psi the relief valve let's water out.
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Old 05-13-2013, 01:15 PM   #4
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No I don't mean leaking water. It is doing it's job. When pressure rises above 100 psi the relief valve let's water out.
Jack.... Sorry... guess I don't know that kinda PRV valve.... I am not familiar with one that releases water when service exceeds a certain pressure... just one's that restrict service pressure.

So... you are normally running 100 PSI in your system??? Wow... seems awfully high to me...

So if that is the situation, I don't understand what the expansion tank will do.... it will just fill up to 100PSI.... and when pressure exceeds 100, your "PRV" pressure reducing (or I guess I should say relief in your case) valve is going to dump water.

Does your valve (PRV) have a drain connection, or does it just leak.
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Old 05-13-2013, 01:54 PM   #5
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We are mixing things up here. I did mean the TPR (little thing on the side of the water heater tank) that releases water when pressure exceeds 100 psi to prevent explosions. It works. When it works it deposits water under the bathroom floor.

I need a PRV (pressure regulator valve) installed but where I install it is the focus of my question.

My question is can a PRV and expansion tank function over pvc over long distances?

The field bathroom is 8x10 and cramped. I don't have space for an expansion tank inside and I don't want to spend money on a PRV. Outside in the winter it gets 20F. All water operations need to be done deep underground to prevent frost damage. I would prefer to install the PRV and expansion tank in the main house where there is a special insulated and heated water closet being built. The main house is still under construction. The only thing that I have qualms about is whether or not an expansion tank will work over pvc underground pipes 100 feet away. That is my question.
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Old 05-13-2013, 01:56 PM   #6
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You have a house. 100 feet away you have a field bathroom. The field bathroom does not have room to house an expansion tank. Can the expansion tank in the house serve the field bathroom as well? pvc is used underground between the house and field bathroom.
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Old 05-13-2013, 01:58 PM   #7
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water company ---> 500 feet ---> house ---> 100 feet ---> field bathroom
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Old 05-13-2013, 02:19 PM   #8
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Here's an illustration of a domestic HW system
The exp tank is normally installed on the CW close to the heater but can go anywhere on the CW, downstream of a PRV, shut off valve or check valve. So, if your outhouse has a CW shut off- the tank needs to be between it and the heater. You don't want it isolated in case the shut of is closed and your tank is still heating
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Old 05-13-2013, 02:31 PM   #9
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Think I understand.... you do not have a PRV (pressure reducing valve) and your TPR (temp/pressure/relief) on your water heater sometimes is discharging water.

Step by Step here: There can be several causes of the TPR valve discharge

1) If you do not have a PRV (which has a check valve effect built into it) and your water pressure is not excessively high, I am surprised a 20 gallon heater is sufficient to create enough over pressure in your system to be releasing a good TPR valve on your water heater.

2) Is your TPR valve excessively old. As said before, they can get weak over time and it might just be that $10 possibly defective/worn TPR valve.

3) Do you think you have excessively high supply pressure. For $8, you can get a wp guage you put on your faucet to check. If your pressure was excessively high, the expansion tank alone will not fix your leak/discharge.... you will need a PRV.

4) If that's the case (excessive WP) and you install a PRV to reduce your system pressure, then because that valve has a check valve effect, your water heater can heat and expand your water such that your internal (house) pressure build beyond the limits of the TPR valve. Thyat's where an expansion tank will become effective.

As in the first post, you need to know whether1) if your TPR valve is excessively old, 2) determine if and where you may have a PRV or any check valve in your system,3) and check your water pressure.

Then we can deduce the cause/cure.
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Old 05-13-2013, 03:05 PM   #10
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My water pressure is 70 psi. That's over the 40-60 psi recommended.
The question by the way was answered by eplumber. He said these devices can be installed anywhere as long as the expansion tank is after the PRV. I understand anywhere to mean it is ok to have a 100 feet distance via underground pvc. That was my question.
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Old 05-13-2013, 03:09 PM   #11
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Quote:
Originally Posted by jackwashere View Post
The question by the way was answered by eplumber. He said these devices can be installed anywhere as long as the expansion tank is after the PRV. I understand anywhere to mean it is ok to have a 100 feet distance via underground pvc. That was my question.
Maybe I wasn't quite clear enough though-
don't have any valves between the exp. tank and heater that could render the exp. tank useless though- such as a service valve to the out building
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Old 05-13-2013, 03:40 PM   #12
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Quote:
Originally Posted by jackwashere View Post
The question by the way was answered by eplumber. He said these devices can be installed anywhere as long as the expansion tank is after the PRV. I understand anywhere to mean it is ok to have a 100 feet distance via underground pvc. That was my question.
Jack... I did not mean to confuse you... just trying to help. I agree entirely with E-plumber that the expansion tank can go anywhere dow3nstream of any PRV or check type valves.

Just trying to save you time/money if it was only a weak/bad TPR valve.
I do note that you never mentioned that your home's water heater TPR valve was discharging too, so I assume it is not. That would generally indicate that either 1) the shed TPR was weak/bad, or 2)you may have some type of checkvalve, back flow preventer, or PRV between your home and shed. (The pressure should be the same at both at both water heaters)

Good to know your WP is not excessive.

Good luck

Peter
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Old 05-13-2013, 06:04 PM   #13
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I also agree with eplumber except...when we get around that 100 foot mark I reccommend going up 1 size in expansion tank..ben sr
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Old 05-13-2013, 06:24 PM   #14
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I also agree with eplumber except...when we get around that 100 foot mark I reccommend going up 1 size in expansion tank..ben sr
Ben... could you explain.... just more room (water) for thermal expansion?

Thanks
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Old 05-13-2013, 06:29 PM   #15
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An Expansion tank is sized by the water heater. Depending on that you should purchase an expansion tank .. Up to 50 gallon HWT an ST-5 expansion tank will work. http://www.amtrol.com/media/document...t_Brochure.pdf

The link above will explain.

Also an Expansion tank can be located anywhere on the cold water. According to the IPC. Some inspectors are into the picture by manufacture of it over the tank but I have had no problems as long as it is on the cold and not valved off.


Last edited by Ghostmaker; 05-13-2013 at 06:31 PM.
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