• Welcome to the new and improved Building Code Forum. We appreciate you being here and hope that you are getting the information that you need concerning all codes of the building trades. This is a free forum to the public due to the generosity of the Sawhorses, Corporate Supporters and Supporters who have upgraded their accounts. If you would like to have improved access to the forum please upgrade to Sawhorse by first logging in then clicking here: Upgrades

expansion tanks

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.
 
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.
 
Last edited by a moderator:
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.
 
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.
 
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.
 
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.
Click to expand...
These actually do not so they "say" no expansion tank is needed. Common sense took hold and said in my opinion you need one.
 
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.
 
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.
 
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.
 
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.
 
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.
 
88twin...see post #14 of mine above as to what happened when a city in Texas decided to install backflow preventers at the meter.
 
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).
 
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
 
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.
 
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...............
 
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.
 
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.
 
You must log in or register to reply here.
Top