No hot water from two downstairs taps

3 Jan 2009
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United Kingdom
Boiler is a Potterton Performa HE30

Upstairs we have;
- Boiler
- (1) Mixer shower
- (2) Mixer tap on sink

Downstairs we have;
- (3) Kitchen mixer tap (9 litres/m - cold)
- (4) Bathroom mixer tap (9 litres/m - cold)
- (5) Bath tap (mixer style but has two knobs) (13 litres/m - cold)

EDIT: I've added my crud measurements for the flow coming from some of the taps above.

The problem we've been experiencing for a while now is sometimes the kitchen(3) and downstairs sink (4) tap don't have any hot water. We had previously noticed this only happened on an evening.

Last weekend I replaced the kitchen tap for a new one as the old one was dripping.

We got sick of the problem, so yesterday a plumber came out and replaced the diaphram on the boiler, this did initially solve the problem (we thought). However this morning we've got absolutely no hot water to taps (3) and (4). If we turns taps (3) and (4) on together, they both then get hot water.

I called the plumber this morning, and he suggested that possibly the mixer shower could be faulty and mixing cold water into the hot. I've been out this morning and bought/fitted a new mixer show. But the problem is still there.

So far we've spent £150 trying to fix this problem and we're out of ideas.

We've had this problem on and off for over a year now, and did have something changed on the boiler a while ago but I don't know what it was. It didn't fix it either.

I'm at a lost as to what the problem might be.

To add, this is the tap I fitted in the kitchen at the weekend;
I've noticed if I remove the aerator from the tap, the water is hot every time from that tap. I've measured flow without the aerator as around 10 litres/m.

Could it be that the water is too restricted on the new tap and the old one was clogged, and maybe the tap in the bathroom is clogged too?

I've also read that the heat exchanger on these boilers get clogged up too?

My plumber tells me that the boiler won't detect water flow below 10 litres per minute, but according to the manual the boiler will work all the way down to 2.5 litres per minute?
Last edited:
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I just wanted to add. I've done further testing tonight. No hot water from kitchen tap, but if I set the heating away by raising the thermostat, then turn the kitchen tap on, we get hot water.

Surely this is a problem with the boiler and not the flow of the taps?

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