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Michael LeavittExpansion tanks have proven themselves to be a great solution for thermal expansion. They are reliable, easily identifiable, and do not cause a bleed-off of expanded water. Watts BRVThat’s right, expansion tanks are the most water conserving solution for thermal expansion.

Watts Description: Series PLT Potable Water Expansion Tanks are designed to absorb the increased volume of water created by thermal expansion and to maintain balanced pressure throughout the potable water supply system. Series PLT tanks feature a pre-pressurized steel tank with an expansion membrane that prevents contact of the water with the air in the tank. This prevents loss of air to the water and ensures long and trouble-free life for the system. These tanks may be used with all types of Direct Fired Water Heaters (gas, oil or electric) and hot water storage tanks. IAPMO listed and ANSI/NSF 61 certified. Maximum Pressure: 150psi (10 bar)


QUESTION #1: Is an expansion tank/valve required? On homes with a closed plumbing system, yes. On homes with an open system, no. Do you know if your home has a closed or open system? If not, call the city building officials and maybe they can help. The water department is a great resource as well. If you have a newer home and live in a metropolitan area, then you can bet that you have a closed system and you need a thermal expansion device. If you have an older home, then it probably started out as an open system, but the water department may have installed a backflow prevention device in recent years to help protect the public water supply. If they did, then you now have a closed system and thermal protection is needed.

Apollow Pressure RegulatorQUESTION #2: If I have a pressure regulator (pressure-reducing valve) installed, but the plumbing system is still an open system to the water main at the street, then do I need a thermal expansion device installed? Yes, unless your state, municipality, or water department has some definitive statement directing otherwise. Since 2003 the International Residential Code has been very clear on this point.

2003 IRC"...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 exceeds the pressure-reducing valve 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..."

Here is the modified 2006 verbiage...

P2903.4 Thermal expansion control.
2006 IRCA 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.

QUESTION #3: Where can I install the expansion tank? Manufacturers are in agreement that they should be installed on the cold water side between the water main shut off and the water heater. They are usually found installed near the water heater, but they do not have to be installed near the water heater.

Watts PRV

LOCATION NOTE: Some states require the expansion tank to be installed within 5’ of the water heater. Check with your building department for your local requirements.

QUESTION #4: Does the expansion tank have to be installed with the label right side up? Check with the manufacturer first, but every professional installation spec I have read says they can be installed in any direction if they are properly supported. Units sold at home centers usually tell homeowners to install them in the vertical downward position because homeowners are lousy at securing and supporting the units into position. They will install them upwards and when the unit is half filled with water then there is extra strain on the securing pipe joints. Remember, if the unit is secured and supported adequately, then they can usually be installed at any angle. If they are not secured adequately, then it is best to install them so they hang straight downward.

AmtrolQUESTION #5: Does the expansion tank have to be secured when installed on a horizontal angle? “I’m surprised I have to splain this to you Lucy!” But sure enough, fellow inspector Michael Wicklund from Puyallup, Wa. stressed that an expansion tank was needed during a home inspection so the installer placed it horizontal with no securing strapping. AmtrolGravity is not a good friend in this situation. The expansion tank was made by Amtrol and their installation documentation only shows up and down installations being suspended from above. I called the Amtrol tech support department and explained the installation Michael encountered and asked for their guidance to which they assured me that you MUST secure their units as needed to take strain off the piping system. This seems like a no-brainer, but installers need to see it in writing before they take any needed steps to comply with logic, so I made the request for Amtrol to put it in writing... HERE IS THE LINK TO VIEW IT IN WRITING (NOTE: Watts shows in their graphic the need to support the unit when installed in the options horizontal position VIEW GRAPHIC).

QUESTION #6: How do I test my expansion tank to see if the internal bladder has failed? Expansion tanks are adjusted during their installation to have similar pressure to the static water pressure. This is done by way of the schraeder valve stem that looks just like the valve stem on a bike tire or car. If you suspect a failed tank, then tap it at both ends. One side should sound hollow and the other should make a thud sound. If the entire unit thuds like it is full of water, then depress the valve stem and see if water comes out. If it does, the bladder has failed and you need to replace the expansion tank.

QUESTION #7: How do I set the pressure of the bladder inside the expansion tank? First check the manufacturer’s guidelines. The short answer is to turn the water off and open a hot water faucet to relief the water pressure. Now test the air pressure... Yes, you should have tested your water pressure first to know what you should have in the expansion tank. If you are doing this yourself, then don’t just buy a tank and install it. If it is not adjusted to your water pressure, then it will not work effectively and will fail prematurely.

From the Watts PRV installation specs...

Watts PRV


Expansion Tank
Pressure Regulators
Thermal Relief Valve
Watts 80M2


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