the small tank is the feed and expansion which keeps the boiler and radiatiors full.two common things that can happen:
1) F&E short of water
(which you say it isn't, presumably you have pressed the ball down and water squirts in, like in a WC cistern? there should be no noticeable sign of water movement in the F&E at any other time)
2) blockage in F&E feed pipe which prevents water going down to refill the system (this is very very very common)
Is the bottom of the F&E thick with rusty mud?
If you bleed the highest radiator in the house, does water squirt out vigorously, with no drop in pressure as you vent it? What colour is the water?
(this is easier and quicker than drawing off a bucket of water from the drain cock and verifying that an equal amount of water is drawn down from the F&E)
I am just a householder but have experienced both these probs
Please note that this involved merely observing, i.e. looking, and not any action, like pushing.The first action is to check that there is sufficient water in the F&E cistern.
If you don't know what that means, please ask.
Am I observing the water level in the large F&E tank or the small one.
The first action is to check that there is sufficient water in the F&E cistern.
If you don't know what that means, please ask.
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