Maintenance and repair of the expansion tank

Maintenance of the expansion tank

Every six months, check for external damage, corrosion, dents, and leaks. If external damage is found, identify and eliminate the cause.
Every six months, check the initial gas pressure Pг to ensure it matches the calculated value. The initial gas pressure can be calculated in the Calculation section of the website.
Every six months, check the membrane integrity, and if damaged, replace it (if it is replaceable).
If the expansion tank is not used for a long period, store it in a dry room after draining all water from it.

Checking the initial gas pressure in the expansion tank. To check the initial gas pressure, disconnect the tank from the heating system, drain the water, and connect a pressure gauge to the gas chamber valve. If the pressure is below the set value, pump the tank using a compressor (possibly a car compressor) through the same valve.

Checking the membrane integrity. If, during the gas pressure check, air escapes through the drain valve after draining the water, and the gas chamber pressure drops to atmospheric, the membrane is punctured.

Possible expansion tank malfunctions

Malfunction	Possible cause	Solution
The pressure in the heating system fluctuates and even at low temperatures exceeds the allowable limit	Lack of compressed air (nitrogen) in the expansion tank	Pump air with a car compressor
-	Damaged membrane	Replace the membrane with the original one (recommended by a service center)
-	Damaged tank body	Repair the body to ensure airtightness (recommended by a service center)
-	The gas chamber valve is not airtight	Blow through the valve and restore the calculated pressure in the gas chamber
-	Insufficient expansion tank volume	Check the Expansion tank volume calculation
Water leakage from the air valve	Damaged membrane	Replace the membrane with the original one (recommended by a service center)
Water pressure is below normal (the heat carrier does not reach the upper point of the heating system)	Lack of compressed air (nitrogen) in the expansion tank	Pump air with a car compressor

Replaceable membrane of the expansion tank

Expansion tank repair. If membrane damage is detected during diagnostics, it must be replaced. Gluing the membrane is not recommended, as the cyclical stretching and compression are destructive to glued joints.

Membrane replacement procedure

Disconnect the expansion tank from the heating system and drain it.
Reduce the gas chamber pressure through the valve at the top of the tank.
Disassemble the membrane flange located near the pipe connection flange. Unscrew the nut at the top of the tank (if present) to release the membrane holder.
Remove the membrane through the hole at the bottom of the tank body.
Check the inner surface of the tank for contaminants and corrosion, remove them, and rinse with water if necessary. Then dry the tank body.
Remember, the membrane is not oil-resistant, so oily substances should not be used for corrosion protection of the inner tank surface.
Insert the membrane holder into the hole at the top of the membrane (if the tank design includes a holder). Tighten the bolt in the membrane holder, insert the membrane into the tank, and place the holder into the hole at the bottom of the tank. Secure the holder with a nut.
Reassemble the membrane flange on the tank body.
Set the initial air pressure in the expansion tank. Check for leaks and reconnect the tank to the heating system.

Attention!

It is best to fill the air chamber with an inert gas such as nitrogen.

Before releasing the gas from the air chamber, the water should be drained from the tank.

The expansion tank’s service life decreases under maximum load and outside the specified temperature range.

Replacement parts should only be original manufacturer parts.