The hot water pressure has always been weak compared with the cold water from the mains, but the boiler "valiant" was able to cope with it and start.
Now on Saturdays and Sundays the pressure of the mains drop as usual (bit I can't really tell if it is dropping more than before), I can't really see any difference in the cold water pressure. It looks like the water going through the boiler to be heated is not strong enough to start it any more. When I turn on the hot water, the boiler doesn't start, but if I push the switch in the boiler that usually is pushed by the pressure of the water, the boiler starts and heats the water.
Is there a way to increase the pressure of the water going into the boiler?