Our Vokera combi boiler is working fine. The heating is working and the water heating fine, but the hot water pressure is too slow taking about 25 mins to run a bath. i have checked the pressure on the boiler which is fine and the mains water is on full. I am aware that the hot water slows in winter as the external water temp is much lower, but it doesn't usually take this long to run a bath.

michael., October 2008

Assuming that the cold water inlet tap to the boiler is fully open it could be that the thimble like filter on the inlet to the manifold that houses the domestic hot water diaphragm is blocked, or that the valve thing behind the domestic water diaphragm is blocked/stuck (take the diaphragm out and you will see it, it is made of white nylon with a spring loaded central element. It unscrews from the brass body, if it is partially blocked then all the water will have to pass through the small metering jet).

See the exploded diagrams at the back of the boiler manual.

If you are unlucky your secondary heat exchanger could be furred up, but that would take a while getting gradually worse.

c, October 2008