I have a small, 6 gallon electric water heater on a project that I'm trying to determine if it needs an expansion tank. My project managers have stated that they have never put an expansion tank on a water heater this small, but I cant find where in the IPC this is stated. To my understanding, every water heater needs an expansion tank regardless of size but in the same breath it makes sense to me that one would not be needed due to non-significant thermal expansion of the water. Does anyone know if the IPC clears all of this up?
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Are expansion tanks required for small water heaters?
- Thread starter asarkisov
- Start date
mtlogcabin
SAWHORSE
An expansion tank is only required when.
607.3 Thermal expansion control.
Where a storage water heater is supplied with cold water that passes through a check valve, pressure reducing valve or backflow preventer, a thermal expansion control device shall be connected to the water heater cold water supply pipe.
No check valve, pressure reducing valve or backflow preventer installed then no expansion tank required.
607.3 Thermal expansion control.
Where a storage water heater is supplied with cold water that passes through a check valve, pressure reducing valve or backflow preventer, a thermal expansion control device shall be connected to the water heater cold water supply pipe.
No check valve, pressure reducing valve or backflow preventer installed then no expansion tank required.
Thank you!
My understanding here is that, based on the situation I described in my original post, I will be needing an expansion tank as the cold water that is being supplied to my little electric water heater comes from a domestic service line that passes through a backflow preventer (albeit a ways away from the water heater, but still there nonetheless.)
FYI for some... certain water purveyors will have a check valve integral to their service meter. If this is the case, the expansion tank is required.
Locally, this pops up because we have three cities very close together, and only one of the cities has a check valve in their meters. Leads to a lot of "Well, the city of ______ doesn't require that?" Education follows.
Locally, this pops up because we have three cities very close together, and only one of the cities has a check valve in their meters. Leads to a lot of "Well, the city of ______ doesn't require that?" Education follows.
Joe.B
Registered User
Recently one of the public works guys in my jurisdiction made an off the cuff suggestion that we start ordering all water meters with the back flow preventers. I had to explain what would happen if they randomly "upgraded" somebody's meter without the appropriate accommodations made to the system. It reality it would mostly be an annoyance for most people, but it helped when I showed him this video (or one like it).
wwhitney
Registered User
If this is the only water heater downstream of that backflow preventer, then yes. If this is a water heater auxiliary to a larger tank water heater which has its own expansion tank, and water can backflow between the auxiliary water heater and the main expansion tank, then at least physics-wise, the main expansion tank can handle both water heaters.
Cheers, Wayne
There is another water heater in this building (2 actually) but they are not hooked up to the same domestic hot water system as the electric water heater.
wwhitney
Registered User
But do they have a common supply on the cold water side?
I.e. if the water in the small water heater expands, can the expansion get to the large water heater's expansion tank through the cold water piping without passing through a "a check valve, pressure reducing valve or backflow preventer"? If so, then the large water heater's expansion tank would be able to take up the small water heater's expansion. [Well, you'd want to check the sizing, if the expansion tank was just large enough for the large water heater, it wouldn't have capacity for the small water heater in addition.]
Cheers, Wayne
That's an interesting point I've never thought about. In theory, the cold water would expand clear out to an expansion source i.e. another expansion tank way down the line. There are no check valves, pressure reducing valves, or backflow preventers between the electric water heater and an expansion tank tied to a much larger water heater.
ICE
Oh Well
In So. California just about everybody has a water pressure regulator and almost nobody has an expansion tank. Those that do have an expansion tank were relieved of approximately $800.00 by a Washington State plumbing contractor. The contractor is really Fast, if you catch my drift.
The customers are prone to asking if the expansion tank is required by the Plumbing Code. I could say, "Well sorta yes and sorta no" But I don't.
The worst is when I have to write a correction for some minor mistake and they fork over another $800.00 for what they are told is a personal preference of the inspector.
One lady was way upset about the expansion tank. She lived there for thirty years without one and knew that she had been scammed. She hadn't paid the invoice as she was waiting to pass inspection. I recommended that she instruct contractor to come and get the expansion tank....I'm quite sure that she did.
I went on a water heater inspection twenty-five years ago. A little old lady met me with all of the paperwork in hand. The invoice stated that she paid $5,800.00 for a forty gallon water heater and that didn't include an expansion tank. The previous water heater lasted almost thirty years. She said that the salesman explained the cost like this: $5,800.00 divided by 30 years = $16.00 per month for hot water...and that seems fair. I guess she was lucky that it failed when it did.
The customers are prone to asking if the expansion tank is required by the Plumbing Code. I could say, "Well sorta yes and sorta no" But I don't.
The worst is when I have to write a correction for some minor mistake and they fork over another $800.00 for what they are told is a personal preference of the inspector.
One lady was way upset about the expansion tank. She lived there for thirty years without one and knew that she had been scammed. She hadn't paid the invoice as she was waiting to pass inspection. I recommended that she instruct contractor to come and get the expansion tank....I'm quite sure that she did.
I went on a water heater inspection twenty-five years ago. A little old lady met me with all of the paperwork in hand. The invoice stated that she paid $5,800.00 for a forty gallon water heater and that didn't include an expansion tank. The previous water heater lasted almost thirty years. She said that the salesman explained the cost like this: $5,800.00 divided by 30 years = $16.00 per month for hot water...and that seems fair. I guess she was lucky that it failed when it did.
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Not sure why you think the contractor was from Washington. Especially considering that California Code requires expansion tanks.
Is this a case of the Tiger Code? A section you've chosen to be unworthy of enforcement?
California Plumbing Code (2022)
608.2 Excessive Water Pressure
Where static water pressure in the water supply piping is exceeding 80 psi (552 kPa), an approved-type pressure regulator preceded by an adequate strainer shall be installed and the static pressure reduced to 80 psi (552 kPa) or less. Pressure regulators for potable water distribution systems shall comply with ASSE 1003. Pressure regulator(s) equal to or exceeding 11/2 inches (40 mm) shall not require a strainer. Such regulator(s) shall control the pressure to water outlets in the building unless otherwise approved by the Authority Having Jurisdiction. Each such regulator and strainer shall be accessibly located aboveground or in a vault equipped with a properly sized and sloped boresighted drain to daylight, shall be protected from freezing, and shall have the strainer readily accessible for cleaning without removing the regulator or strainer body or disconnecting the supply piping.
Pipe size determinations shall be based on 80 percent of the reduced pressure where using Table 610.4.
An approved expansion tank shall be installed in the cold water distribution piping downstream of each such regulator to prevent excessive pressure from developing due to thermal expansion and to maintain the pressure setting of the regulator. Expansion tanks used in potable water systems intended to supply drinking water shall comply with NSF 61. The expansion tank shall be properly sized and installed in accordance with the manufacturer's installation instructions and listing. Systems designed by registered design professionals shall be permitted to use approved pressure relief valves in lieu of expansion tanks provided such relief valves have a maximum pressure relief setting of 100 psi (689 kPa) or less.
608.3 Expansion Tanks, and Combination Temperature and Pressure-Relief Valves
A water system provided with a check valve, backflow preventer, or other normally closed device that prevents dissipation of building pressure back into the water main, independent of the type of water heater used, shall be provided with an approved, listed, and adequately sized expansion tank or other approved device having a similar function to control thermal expansion. Prepressurized water expansion tanks shall comply with IAPMO Z1088. Such expansion tank or other approved device shall be installed on the building side of the check valve, backflow preventer, or other device and shall be sized and installed in accordance with the manufacturer's installation instructions.
A water system containing storage water heating equipment shall be provided with an approved, listed, adequately sized combination temperature and pressure-relief valve, except for listed nonstorage instantaneous heaters having an inside diameter of not more than 3 inches (80 mm). Each such approved combination temperature and pressure-relief valve shall be installed on the water-heating device in an approved location based on its listing requirements and the manufacturer's installation instructions. Each such combination temperature and pressure-relief valve shall be provided with a drain in accordance with Section 608.5.
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jar546
Forum Coordinator
Expansion control is required regardless of the size of the storage water heater. An expansion tank is ONE METHOD, there is more than one way to accomplish this. Almost every structure in the US has a backflow preventer at the water service or at least a check valve at the well tank/pump system. If you can't fit a tank, there are approved valves used in many jurisdictions.
Just to be clear though, a standard TPR valve on a water heater is not an approved method.
ICE
Oh Well
The contractor’s address was a clue. I had to call a Washington State phone number to explain the value of requesting an inspection.
That’s a fair assessment.
It’s not like I never ask for an expansion tank. Sometimes there’s a long run of pipe in an attic or even on a roof. Are you sure that a standard pressure regulator prevents excess back-pressure from dissipating into the water service pipes? I don’t have that answer but given that .001% of the water heaters are equipped with an expansion tank, I suspect that there is an accommodation built in.
This is an apartment building. The pipe to each unit is on the exterior. An expansion tank was required...maybe more than one. I was only there because the plumber lit the place on fire and that city's inspector wasn't available. I probably shouldn't say that he was a plumber.....he more likely identifies as an electrician.
On a sunny day it might take a while to get cold water at the shower head.
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jar546
Forum Coordinator
You are correct.
jar546
Forum Coordinator
This is one of the approved devices.
www.sharkbite.com
Thermal Expansion Relief Valve
Replaces an expansion tank, shut-off valve and fitting when installing or servicing a water heater.
www.sharkbite.com
jar546
Forum Coordinator
Here is another one that we have approved for use in lieu of an expansion tank.
jar546
Forum Coordinator
And there are even more that we have approved in lieu of the old expansion tank method that takes up too much space.
Remember. The code says expansion control required, not expansion tank required.
Remember. The code says expansion control required, not expansion tank required.
ICE
Oh Well
If there is no outward sign of a mechanical control and also no outward sign of a problem....what then? How do we justify adding an expansion control in the face of thirty years of nakedness? Oh but there is a code you say! My bad, I'm so sad, I wish you had expansion control.
jar546
Forum Coordinator
ICE
Oh Well
Southern California has expansive soil and it appears that Florida has expansive water.…or is it an expansive code. I hear your argument for strict adherence to written code which would force me to argue with decades of success.
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Inspector Gift
Sawhorse - Made in USA
Our town has grown so fast that the Public Works department has raised the water supply pressure to keep up with the demand. The PW Department has also changed all the water meters to allow remote monitoring. All the water meters now have internal check valves. Consequently, we have witnessed many new homes with supply water pressures that were over 100psi, and a handful around 130 psi. We now require PRV's (Pressure Reducing Valves) at all new homes. However, we have not required older homes to install PRVs or Expansion Tanks.
I have seen homes with PRV's that also had the tell tale signs of leaking Temperature/Pressure Relief (TPR) valves at the water heater due to no expansion tanks. And over the years, more than a dozen people have complain of the toilets valves frequently relieving the pressure, usually in older homes that did not have expansion tanks. After the expansion tanks were installed, the problems went away.
IMHO, the Myth Busters Video is not applicable to this OP's question. I was given to understand that water expansion tanks will NOT prevent a water heaters from exploding. That is the function of the TPR valve.
But maybe things work differently in IPC land. ;^ )
I have seen homes with PRV's that also had the tell tale signs of leaking Temperature/Pressure Relief (TPR) valves at the water heater due to no expansion tanks. And over the years, more than a dozen people have complain of the toilets valves frequently relieving the pressure, usually in older homes that did not have expansion tanks. After the expansion tanks were installed, the problems went away.
IMHO, the Myth Busters Video is not applicable to this OP's question. I was given to understand that water expansion tanks will NOT prevent a water heaters from exploding. That is the function of the TPR valve.
But maybe things work differently in IPC land. ;^ )
jar546
Forum Coordinator
We too had a requirement for PRVs in homes with pressures that exceeded 75psi. The Federal Clean Water Safety Act, I believe all State Statutes and the Plumbing code all required protection of public water systems and backflow preventers are one of the most common methods used. If a home is protected with a backflow preventer then a storage tank water heater requires expansion control.