I have a strange problem with my kitchen mixer tap. I have a gravity-fed system with tank in the loft and indirect cylinder in the upstairs airing cupboard. There is a whole-house pump on the floor of the airing cupboard. Upstairs the hot water to bath, basins and shower work fine. Downstairs there are two mixer taps; one in a cloakroom and the other in the kitchen. The hot supply to the cloakroom is also working okay. However, when turning on the hot tap in the kitchen, there is either a long delay (>30 secs) before any water comes out or else the hot doesn’t work at all. That is, unless the cloakroom hot is briefly turned on first, in which case the kitchen flow starts immediately. I assume this is sufficient to get the pump working. Does anyone have any ideas as to the cause of this problem and how to cure? Thanks!