Hot water going cold and no hot water from bathroom tap

[ShaunShep]

We've had this combi boiler fitted for the last 7 year or so and never really experienced any issues. However a few month ago we started seeing some problems.

The first, we have a mixer tap in the bathroom which when turned to hot no longer gives off any hot water. The boiler simply isn't firing up. If at the same time we turn on our mixer shower, then the tap and the shower both give off hot water. It's like the boiler isn't detecting that the tap is on. At first we suspected an issue with the mixer tap, but have also started to notice other problems.

If one of us is in the shower, and someone turns on a cold water tap elsewhere in the house, then the shower water goes cold. I've noticed this with other taps too. This hasn't been an issue before, normally if you are in the shower and someone turns on a tap, the pressure drops but it's still hot.

We've recently had the boiler serviced and I raised these issues with the person servicing the boiler. He said that the boiler switches on the hot water when it detects a drop in pressure, which I understand. He didn't think we had a problem and suggested it would the mixer tap in the bathroom that was at fault.

Given the other issue we seem to be having that we've never had before, I can't help but think that something in the boiler is faulty and it's not detecting the change in pressure as accurately as it once was.

I'm wondering if anyone could suggest what the issue may be so I can approach someone to at least attempt to repair the boiler.

 

[picasso]

I could suggest you tell us the make and model of your combi boiler, it really would help.

 

[muggles]

Nope, can't see the make or model of the boiler I'm afraid - you're going to have to give me a clue...

Might be a shower fault, but let's start worth the boiler

 

[TheBinarySheep]

Sorry it's a potteron performs HE 30

 

[DP]

You will see a row of lights marked 30 to 80 behind the flip down cover
Then there are four light below that
One of the lights has a tap symbol

When you run any hot tap, the tap symbol light on the boiler will Illuminate

If your cold supply is poor, there will be a reduction in hot water flow if a hot or cold tap is run elsewhere

For good mains pressure, any hot tap should give you about 11 litres per minute. Run any hot tap full flow and collect water in a bucket aver 15 seconds. What you collect in the bucket, measure that. Four times that is what your boiler is able to supply

If you get hot water elsewhere, not at the bath tap, (check light on boiler), then faulty tap

 

[TheBinarySheep]

I've measured the flow at around 9 litres per minute.

I'm just finding it strange that we've not have any of these problems for 7 year, and now we do. Is it possible the mains supply pressure has dropped recently and that's causing the issues.

It's a right pain, because now if someone is in the shower, we can't use any other taps, dishwasher washer. Where as we could before.

I've done a test this morning where I've put the shower on, and then turned a tap on elsewhere in the house. The 'tap' light on the boiler goes off and the shower goes cold. I've then measured the flow from the shower to be around 7.5 litres per minute.

 

[muggles]

Sounds like a shower problem to me after that description - do you have supply isolators on your shower?

 

[DP]

I've measured the flow at around 9 litres per minute.

Your boiler should be delivering 12l per minute
Boiler will activate for HW when 2.5l is flowing from a hot tap

I think there is a filter on cold water inlet that could be blocked
Hole in the diaphragm could be an issue
The component that creates differential pressure could be goosed

You really need a boiler repairer to have a look at the boiler

 

[TheBinarySheep]

Come to think of it, we do have a lime filter on the cold water feed and I wonder if that's become blocked like you say.