Hot water cutting in / out

StudWall · 11 Oct 2020

Hi all,

hoping someone can point me in the right direction with an issue i'm having with my hot water system.

Boiler is a Worcester combi about 5 years old, never had a single problem until recently.

The shower is built into the bath tap with a lever to switch to shower head, like this one:

Bath-Taps-Wickes-Classic-Bath-Shower-Mixer-Tap-Chrome~GPID_1100203051_00

To get the right water temperature the hot tap goes all the way on and the cold about half a turn. Has always worked just fine.

Recently the boiler has been cutting out after a minute or two. It takes about 15-20 seconds for the water to heat up (normal) then you get about 2 minutes of correct temperature water before it goes freezing (boiler has turned off). Turn the cold tap off for a moment and it comes back to life.

Sometimes it does this just once and sometimes it happens several times.

I've made sure nothing else in the house was running water at the same time and the problem still happens

terryplumb · 11 Oct 2020

Run the shower,and set the two taps to blend to the temperature that you want . When required temp is coming from the shower head, try pushing/ pulling on the tap heads to see if there is any play ,and if the flow from shower head alters.
If it does replace the tap valves.

martyndc88 · 11 Oct 2020

Does your boiler have an LCD display? Id imagine it does. What does the temperature reading on that get to when you're running the hot water

StudWall · 11 Oct 2020

Thank you for the suggestions!

terryplumb said:
Run the shower,and set the two taps to blend to the temperature that you want . When required temp is coming from the shower head, try pushing/ pulling on the tap heads to see if there is any play ,and if the flow from shower head alters.
If it does replace the tap valves.

Nothing untoward on the taps, they feel firm, no movement on the heads.

martyndc88 said:
Does your boiler have an LCD display? Id imagine it does. What does the temperature reading on that get to when you're running the hot water

Yes, i've just given it a try now (the water temp on the boiler is set to 60 which seems to be the maximum)

When running it went up to 68 then slowly came back down over the space of a minute and settled at 64 where it sat for another minute, before i stopped. My assistant noted the water stayed warm.

Think i'll have to try it a couple more times and see if i can catch it out.

I have just been reminded that i replaced the shower head a few weeks ago ... wonder if that has anything to do with it

martyndc88 · 11 Oct 2020

I would imagine that you're restricting the flow on the hot water so much that it can't modulate down low enough to keep a constant temperature.

StudWall · 11 Oct 2020

martyndc88 said:
I would imagine that you're restricting the flow on the hot water so much that it can't modulate down low enough to keep a constant temperature.

Good shout, sounds logical. Might be explained by these modern water saving shower heads. I took the hose off and noticed the inlet hole was quite small so I've drilled it out to 10mm.

Will see if that makes any difference

Bodd · 11 Oct 2020

Sounds like the heat exchanger on the combi

terryplumb · 11 Oct 2020

Is it only the shower ? When that mixer is used to fill the bath ,does boiler give constant temperature hot water ?

StudWall · 11 Oct 2020

As far as I know it's only the shower, I dont use the bath and it usually runs long enough to fill the sink up for a shave so showering is the only time I notice it

terryplumb · 11 Oct 2020

If all hot taps give constant hot temp when left running your boilers ok,and the bath/ shower mixers the issue.

Bodd · 11 Oct 2020

Its normally the shower that we discover the problem as we are under it.
We leave the bath to run and the sink to fill. and have a quick wash at the basin

StudWall · 14 Oct 2020

martyndc88 said:
I would imagine that you're restricting the flow on the hot water so much that it can't modulate down low enough to keep a constant temperature.

Seems like that was the issue, I drilled out the flow restrictor on the shower head and also fitted a new hose with a much larger bore and now the shower is much better, and also the hot doesn't seem to be cutting out.

Thanks!

diynot

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Hot water cutting in / out

Bodd

Bodd

Similar threads