# expansion tanks



## pwood (Nov 16, 2010)

when exactly are expansion tanks required on water heaters? type of fuel,capacity, closed system?


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## Jobsaver (Nov 16, 2010)

In my ahj, whenever it is on a closed system. Our water purveyor does not install any type of device at the meter, so the utility is not a closed system. On the propert owner's side of the meter, if a RPZ, check valve, or other device is installed upstream of the water heater, an expansion tank, or expansion valve is required.


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## texas transplant (Nov 16, 2010)

From the 2006 IPC

607.3 Thermal expansion control.

A means of controlling increased pressure caused by thermal expansion shall be provided where required in accordance with Sections 607.3.1 and 607.3.2.

607.3.1 Pressure-reducing valve.

For water service system sizes up to and including 2 inches (51 mm), a device for controlling pressure shall be installed where, because of thermal expansion, the pressure on the downstream side of a pressure-reducing valve exceeds the pressure-reducing valve setting.

607.3.2 Backflow prevention device or check valve.

Where a backflow prevention device, check valve or other device is installed on a water supply system utilizing storage water heating equipment such that thermal expansion causes an increase in pressure, a device for controlling pressure shall be installed.


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## Uncle Bob (Nov 16, 2010)

Closed system

Uncle Bob


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## Glennman CBO (Nov 17, 2010)

Agreed, closed system.

Also, an expansion tank is not the same as a pressure relief valve. A pressure relief valve is always required, and an expansion tank is only required in a closed system.


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## Mule (Nov 17, 2010)

We have a subdivision that has excessive water pressure so we require a pressure reducing valve. Now this doesn't make a closed system but since the pressure is higher on the incoming side than the outgoing we require an expansion tank.

Our thought on this is even though the PRV will allow water to backflow into the city system when the water expands it will not because the pressure is higher on the city side. The water has to expand somewhere so...expansion tank.

The reason I post this is because this type of system is not a closed system but in my opinion the circumstances create a situation where a expansion tank is needed.


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## pwood (Nov 17, 2010)

thanks to all who responded for the help. texas t, are those ipc code sections?


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## DanB (Nov 17, 2010)

The pressure reducing valves I've worked did function as check valves also.  I would always require an expansion tank in the system if present.


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## texas transplant (Nov 18, 2010)

That is the 2006 IPC sorry forgot to say that before.


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## Mule (Nov 18, 2010)

DanB said:
			
		

> The pressure reducing valves I've worked did function as check valves also.  I would always require an expansion tank in the system if present.


These actually do not so they "say" no expansion tank is needed. Common sense took hold and said in my opinion you need one.


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## peach (Nov 20, 2010)

probably always a good idea


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## 88twin (Dec 16, 2010)

cpold be a dumb question... is it a closed system if there is a sprinkler sys. (irrigtion not fire)


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## texas transplant (Dec 16, 2010)

88,

No, closed system with a water heater that would cause thermal expansion is where expansion control is required.   We  have a requirement that the irrigation system be isolated from the domestic water system with an RPZ, at a minimum,but since the  sprinkler system has no water heater, thermal expansion is not an issue.


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## Mule (Dec 17, 2010)

It all depends on where you install the backflow prevention device. If it is on the main sevice line going to the house, then yes it would be a closed system. If it is on a branch off of the main line then no, it is not a closed system.

I remember a few years back, Denton, Texas I believe, started installing water meters with a backflow device. All of the older homes started having troubles. Joints started leaking inside the walls, yard lines were busting, all because of a closed system. The older pipes and joints could not take the additional pressure being created.


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## 88twin (Dec 17, 2010)

thank you for the response. the debate here was if it was a closed system if it had a sprinkler

line. I was getting out voted so I thought I'd "ask the experts".

not that it will probably do any good in the debate , but at least I'll know.


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## Dr. J (Dec 17, 2010)

88twin - tell the debaters to look at the arrow on the backflow preventer.  If it points toward the water heater - the expanded water can't get past it creating a closed sytem; if it points away from the water heater  - open system.


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## 88twin (Dec 17, 2010)

ahhh Dr.J, as you and fatboy know my city is at 6,000+ elevation.

all the areas I have worked and played the last 35 years, if we had an

irrigation system- open, no irrigation system AND rpv then closed.

at this elev. it's common to close the ball valve and shut down the sprinklers for the winter so...

now it's closed.

never mind the fact there have been no NO problems or complaints for 40 years,

"someone" just found the requirement in the code so it must be enforced.

granted the better plumbers do use expansion tanks at W/H and the city is replaceing water meters

throughout town, installing an RPV at all services.

typical water pressure here is approx. 120psi, and has been for years.


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## Mule (Dec 20, 2010)

88twin...see post #14 of mine above as to what happened when a city in Texas decided to install backflow preventers at the meter.


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## Dr. J (Dec 21, 2010)

The backflow preventer, and the ball valve to isolate the irrigation system do not make for a closed system anymore than the angle stops or faucets on each plumbing fixture.  The "goes-outta" end of a building's domestic water system is always closed, it is the "goes-inta" that could be either open (allows expanded water back to the city main) or closed (prevents expanded water back to the city main).


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## mtlogcabin (Dec 21, 2010)

A few years back the public works was getting complaints of exccessive water bills, They concluded that the newer homes without water hammers did not allow for expansion which the water heater was causings and was thus resulting in the water meter "rocking" back and forth. The meters only register flow in one direction. The solution was install an expansion tank and the problem was solved. So there are other reasons an expansion tank may be a good idea even on an open system


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## mtfd7561 (Mar 2, 2011)

So this may be a stupid question but then I would assume that a home with private water (well) would still be a closed system and would still require an expansion tank? No back flow preventer on the well pump.


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## Mule (Mar 2, 2011)

That's one of those.....hmmmmmmmmms.

There is some kind of check valve in the well to keep the water from siphoning back into the well sooooo water has to expand somewhere. I don't know too much about wells so...............


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## texas transplant (Mar 2, 2011)

Mule, I agree hmmm....., guess it would depend on the setup, however if the pump fills a pressure tank, could that pressure tank be the expansion tank as well.   Don't know whether I can find that in the code or not, but for some reason it makes sense here at the end of a long day.    Seems the code simply says "a device to control the thermal expansion" doesn't say what or give a specific standard that the device must comply with.


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## Dr. J (Mar 2, 2011)

The pressure tank _could_ take the place of an expansion tank, if it has the extra capacity to hold the expanded water, in addition to the required holding capacity of the tank and the pump cut off is sufficiently below the max system pressure.


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## GHRoberts (Mar 2, 2011)

We have a well. So I know about those.

The pressure tank acts as an expansion tank. I guess we could do some math on a typical tank. A 20 gallon tank set for a low pressure limit of 50psi and a high pressure limit of 100spi. (I think my tank is set for 60 and 80 but the math is more difficult.) The pump starts when the tank is empty and the pressure is 50psi. It pumps 10 gallons of water making the pressure 100 pounds and turns off. 1 gallon of water expansion would raise the pressure from 100 psi to 111psi (100*(10/9)). I don't think 110psi will trip the TP valve on the water heater.


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## Dr. J (Mar 2, 2011)

100 psi is already over the limit (80 psi).  The pump cut off needs to be lower than 80 to suck up the expansion without going over 80.


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## M. Nieves (Jun 29, 2018)

pwood said:


> when exactly are expansion tanks required on water heaters? type of fuel,capacity, closed system?



Hi, pwood, as far as I know, If your domestic hot water heating system doesn't have a functional expansion tank, swings in water pressure can take years off your tank’s integrity. This could cause leaking or bursting of your tank because the glass lining of the water heater gets stressed and damaged.

Also, your expansion tank should be checked annually if you want to avoid and prevent premature failures.


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## Rick18071 (Jul 5, 2018)

I live in a community of 20 houses that are off 2 wells that fill a tank on top of a hill. I'm near the top of the hill so don't have a lot of pressure. The homes near the bottom of the hill are on a pressure limiting device because it get to about 100 psi. No one ever had any water hammering anywhere that I know of. Would anyone require itr here?


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