Odd hot water problem

[Summersport]

For a few weeks our shower has been temperamental, only getting hot when the shower room sink tap is running too. We had the boiler checked out, but nothing was found. Then the kitchen sink started doing the same thing, only getting hot when the shower room tap was running. And today we have no hot water at all; even the magic tap trick isn’t working anymore. Does anyone have any clues as to what is going on?

Either insufficient flow through the tap/shower, or the flow switch in the boiler is not detecting the tap is on.
It's not an expensive part but the fitting will be a couple of hours I'd have thought

Thank you, Johnd2.

Do you mean that in either case ( insufficient flow or lack of detection) I might need a new flow switch, and that this would take a couple of hours to fit?

You've got a combi, haven't you?

Yes, it might be the flow switch, or it could be poor flow.

Does the hot bath tap have the same problem? Baths taps are (should be) bigger and have greater flow.

Run the shower into a bucket, time it to full, calculate litres per minute.

If the shower head is clogged with limescale, it will reduce the flow, so measure it again with the head taken off. If the head is the problem, unscrew it and immerse in a bowl of descaler fluid, or throw it away and buy a new one with rubbery jets.

You've got a combi haven't you?

I was just coming on to say the same thing. Ours does it too. Randomly. It is a pain in the neck.

Thank you Piglet John, we do have a combi; but give it’s the kitchen tap as well as the shower that’s not working, so presumably that would rule out a shower limescale problem?

If multiple hot taps in the house are on and plenty of water is coming through, and it's still not firing, then it'll be a problem in the boiler. Probably the flow switch.

If taps are only delivering a light flow then the problem will likely be else w where eg taps blocked with lime scale or some other restriction.

Apparently the boiler engineer is going to put a “turbo-float” into the boiler, but thinks that the shower thermostat might be broken, and that this is affecting every tap in the house. Am hoping that shower thermostats are easy and cheap to fix...?

try the bucket test please. How many LPM from the hot tap? And the cold tap?

He’s turned the hot water off and is coming back tomorrow, so I’ll have to try it then.