Home » Hot Boiler Expansion Tank: Troubleshooting

Hot Boiler Expansion Tank: Troubleshooting

by Kamal Salar

Have you ever wondered why it is necessary to install an expansion tank with a furnace? There is a simple fact; water expands when it is boiled. So if you have not installed an expansion tank, relief valve is surely going to be blown off with the pressure built inside the tank by expanded water.

How does an expansion tank work?

Expansion tank absorbs the pressure. The process is simple. The air inside the boiler lets the expanding water in the tank to compress. This prevents the tank to regulate the pressure building up inside the tank by heating and cooling of water. If the relief valve is removed or plugged in, it might only not jeopardize the person doing it and the system as well. Removing or plugging in the relief valve causes great pressure inside the system, which might cause huge explosion and damage to water heaters, fittings and lines. Relief valve is a diaphragm which has partial air inside it. This air pressure inside the diaphragm is adjusted according to the pressure and expansion of water inside the tank.


Image credit: Brian Snelson

What problems can occur inside the tank?

Ideally hot boiler water tanks work excellent for 6-10 years. But when the tank start wearing out, it becomes necessary to change the fittings. Usually when a tank wears out it starts leaking. Fixing the leakage problem is not very difficult, you can simply do it yourself. You can buy the fixtures and fittings online easily simply by going to www.autopecasstore.pt.

How to fix the leakage problems in the boiler expansion tank?

The first step is to find the source of leakage. Locating a leak is easy. If you are unable to find the point of leak, take soupy water in a bowl and pour it over the wet areas. The point of leakage will start bubbling. After locating the source you can start repairing work.

Before starting repair, ensure you have cut off gas feeders, disconnected all electric plugs, and turned off the water valves. Turn off the hot water circulating pump and bring the valve to return line. Connect drain valve to the drain hose to remove some water, which might be causing pressure inside the tank. Now see if the pipes are leaking. To repair the leaks, you would need to open the pipe connections and clean the joints. You can use any plastic scratch pad. Assemble the pipes together and wrap a clean plumber tape around the connections. Turn the water boiler on and ensure the pressure reading is 10-12 PSI. In case you don’t get this reading, there is another leak in the tank.

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