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How to Properly Adjust the Pressure in our Expansion Tank?

Every closed system has an expansion tank. We will see how to properly adjust the pressure in our expansion tank so that our system works properly. The first step is getting a water pressure gauge like this and opening a hose bib or water spigot that is regulated, meaning it's the same system that's in your house, not the one from the road.


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We dial the gauge in at about 65 psi so now we need to adjust the expansion tank to be 65 psi as well. We go ahead and turn off the water and disconnect this pressure gauge and then the next step is draining the water from this bib.

 

On the bottom of the expansion tank there's a plastic cover that unscrews and reveals a valve stem. We're going to check the pressure in our tank but first to do that we need to turn off the main cut-off valve for our home and drain all the water using the spigot outside  The purpose of this system is whenever the water expands from being heated in the water heater it can overflow into the Expansion Tank. Since we have a closed system that water has no way to get back through these valves into the main water system. So there is a diaphragm inside that takes up about half of the tank and we need to make sure that the psi in that diaphragm matches the psi in our water system.

 

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We take a standard air gauge and see that the air pressure is very low there. It should have been around 40 psi.

 

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So we take an air chuck connected to a compressor and put some air in the tank. If you don't have an air compressor you can use a bicycle pump. We continued adding small amounts of air to the tank until we got up to 65 pounds of pressure.

 

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Lastly, we just need to screw the protective plastic cap back onto the valve stem so the expansion tank doesn't get damaged.

How to Properly Adjust the Pressure in our Expansion Tank?