Ask Boiler or System Questions. Leave CommentsHow to drain you expansion tank
I would like to start by saying you should not have to drain your expansion tank if properly installed. For proper installation see the link. The easiest way to determine if the tank needs draining is to monitor the pressure while the boiler is running. The pressure should not change much from a cool start to a hot shutdown. The pressure should not change more than 5 psi. When draining the tank, you must always completely drain the tank of water to get the proper air charge
How to drain the tank.
1. Turn the boiler off
2. Close the valve to isolate the tank from the system (1)
3. Connect a hose to the tank drainer (2) or drain valve if no tank drainer
4. Open valve
5. Drain until the water stops draining and open the vent on the side of the drain valve (3). If there is no vent, loosen the hose slightly to allow air to get into the tank. If that doesn't work, drain the tank with a bucket to allow air to enter and break the vacuum.
6. When the tank is empty, remove the hose. I like to do this before closing the tank valve to verify that the tank is completely drained. Close the tank valve.
7. If you removed the plug, replace the plug, verifying it is tight so no air will leak out of the tank when the tank is pressurized.
8. Open the system isolation valve slowly to allow the tank to refill. You should hear the auto-feeder start to feed if you have one. The water pressure should shut down somewhere around 12 psi for a two-story home or less. Never operate below 12 psi. For three or more stories, you will need higher water pressure.
Note: If the auto feed valve does not feed make-up water, it may need to be serviced or replaced. If you have a manual valve, you may feed the water in with that to 12 psi.