water heater expansion tank

[daniel nantell]

when Inspected a hot water heater that does not have a expansion tank installed, is it correct to recommend a expansion tank be installed for safety and proper operations, some communitys require a tank added when the older water heater is replaced.

[Jim Luttrall]

It depends on the code the water heater is under. IRC only requires an expansion device when there is a closed system (check valve.) If no closed system, no thermal expansion device is required, of course if you live in the land of slab foundations with pressure regulators buried in the yard it is really difficult to know.
I always measure the static water pressure and recommend installation of a pressure regulator and expansion tank if the pressure is more than 80 PSI.

[Gunnar Alquist]

when Inspected a hot water heater that does not have a expansion tank installed, is it correct to recommend a expansion tank be installed for safety and proper operations, some communitys require a tank added when the older water heater is replaced.

Like Jim said. I believe it is also required when the house is on a well. Maybe not if it is gravity fed, but when there is a bladder tank. This would be true with homes that have a booster pump as well.

[Bruce King]

I can't think of the right term, but if the system has a small bleeder valve with a small clear hose usually to the exterior this takes the place of the expansion tank. I see these on many new homes.

[Scott Patterson]

I can't think of the right term, but if the system has a small bleeder valve with a small clear hose usually to the exterior this takes the place of the expansion tank. I see these on many new homes.

It is an expansion valve, it is less expensive than a tank and it's purpose is the same as a tank. You just need to have a place to put the water that comes out of the valve(tube). On my home it goes outside, right next to my TPR discharge line.

[Paul Johnston]

Like Jim said. I believe it is also required when the house is on a well. Maybe not if it is gravity fed, but when there is a bladder tank. This would be true with homes that have a booster pump as well.

If you have a well, bladder tank and no check valve why would you need an expansion tank?

[Mike Schulz]

You have a foot valve but that is before the bladder and you would think the bladder tank would be the same as a expansion tank. From what I have read a 40 gallon water tank will expand a half gallon.

So what's the verdict plumbers, do you need a expansion tank on a well system?

[Fred Weck]

Per the IRC an expansion tank is not needed for a water heater, whether there is a well, or it is city water. An expansion tank is required for a boiler as a part of a hydronic heating system:

M2003.1 General. Hot water boilers shall be provided with
expansion tanks. Nonpressurized expansion tanks shall be
securely fastened to the structure or boiler and supported to
carry twice the weight of the tank filled with water. Provisions
shall be made for draining nonpressurized tanks without emptying
the system.

M2003.1.1 Pressurized expansion tanks. Pressurized
expansion tanks shall be consistent with the volume and
capacity of the system. Tanks shall be capable of withstanding
a hydrostatic test pressure of two and one-half times the
allowable working pressure of the system.

M2003.2 Minimum capacity. The minimum capacity of
expansion tanks shall be determined from Table M2003.2.

First post, be kind!

[John Arnold]

From a thread in the archives:

IRC P2903.4 Thermal Expansion. In addition to the required pressure relief valve, an approved device for thermal expansion control shall be installed on any water supply system utilizing storage water heating equipment whenever the building supply pressure is greater than the required relief valve pressure setting or when any device, such as a pressure reducing valve, backflow preventer or check valve, is installed that prevents pressure relief through the building supply. The thermal expansion device shall be sized in accordance with the manufacturer's installation instructions.

[Fred Weck]

That section has been amended in the 2006 IRC:


P2903.4 Thermal expansion control. A means for controlling increased pressure caused by thermal expansion shall be installed where required in accordance with Sections P2903.4.1 and P2903.4.2.

P2903.4.1 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.

P2903.4.2 Backflow prevention device or check valve. Where a backflow prevention device, check valve or other device is installed on a water supply system using storage water heating equipment such that thermal expansion causes an increase in pressure, a device for controlling pressure shall be installed.

[Scott Patterson]

Just take a few seconds and think about the water heater and what is connected to it. If the water inlet line has any device that has a "check" valve or device that keeps the water from backing up the line then you need to have an expansion tank or valve on the line.

The water expands in the water heater, it has to go somewhere so it can't then you need something that will allow it to expand.

[Mike Schulz]

Scott,
So if I am reading into to this right, if it's on a well and there is no check valves after the bladder tank a Expansion tank is not needed........

A bladder tank has lots of room for expansion does it not?

[Fred Weck]

Mike, use this link: http://www.blueridgecompany.com/documents/Watts-ThermExpansion.pdf
It shows installation requirements for when a tank is required, it also shows a cut away of expansion tanks, a well pressure tank is constructed the same way as a expansion tank. I think your covered unless a check valve is installed between the pressure tank and the water heater.