Hot water pressure issue

[ajt2018]

I have a Worcester heatslave 15/19 oil fired boiler. The expansion tank was recently replaced however I am still having issues where the hot water pressure is not consistent.

Examples being you run the kitchen tap and it seems to take a while for the hot water to come out but then when it does come out it runs hot and is fine.
In addition we have an oldish triton shower which has a thermostatic mixer the water from the shower will run hot for a while then runs cold and goes in this repeated pattern. I am confident that there is no issue with any fault on the shower, when the shower is running you can feel the hot water pipe elbow joint next to the shower unit and can feel the pipe going from hot to cold in sync with the hot and cold water coming out the shower head when it should just be consistently hot.

All the radiators were bled after the expansion vessel was fitted and the bled valves on the boiler have also been bled. The motor is fine therefore after doing lots of research on the net so far I am still trying to find out what could be causing this.

Any suggestions would be appreciated. Thanks

 

[SimonG]

So is the issue pressure or flow or temperature?

 

[ajt2018]

So is the issue pressure or flow or temperature?

Simong - thanks for responding. From what you have said the flow of the water doesn’t change the temperature just drops. When you feel the shower pipe you can feel the temperature very quickly dropping from hot to cold and then the reverse about 5-10 seconds later. Thanks

 

[SimonG]

It's the shower.

 

[ajt2018]

It's the shower.

Simong ok thanks will look into it further

 

[oilman]

I have a Worcester heatslave 15/19 oil fired boiler. The expansion tank was recently replaced however I am still having issues where the hot water pressure is not consistent.

Examples being you run the kitchen tap and it seems to take a while for the hot water to come out but then when it does come out it runs hot and is fine.
In addition we have an oldish triton shower which has a thermostatic mixer the water from the shower will run hot for a while then runs cold and goes in this repeated pattern. I am confident that there is no issue with any fault on the shower, when the shower is running you can feel the hot water pipe elbow joint next to the shower unit and can feel the pipe going from hot to cold in sync with the hot and cold water coming out the shower head when it should just be consistently hot.

All the radiators were bled after the expansion vessel was fitted and the bled valves on the boiler have also been bled. The motor is fine therefore after doing lots of research on the net so far I am still trying to find out what could be causing this.

Any suggestions would be appreciated. Thanks

 

[oilman]

I think the heatslave 15/19 might be a combination boiler. This could be a diverter valve problem or scale. Please confirm The one you have is a combination boiler.

 

[SimonG]

It is a combi. If it was scale you would have reduced flow. If it was divertor than hot water isn't affected but you would get warm rads with heating off.

 

[ajt2018]

It is a combi. If it was scale you would have reduced flow. If it was divertor than hot water isn't affected but you would get warm rads with heating off.

The diverter valve cartridge and the actuator were both replaced not that long ago for a different issue.

 

[ajt2018]

It is a combi. If it was scale you would have reduced flow. If it was divertor than hot water isn't affected but you would get warm rads with heating off.

Simong- we definelty have no issues with warm radiators they get hot as normal.

 

[SimonG]

Definitely the shower

 

[ajt2018]

Simong ok thanks will look into it further

In relation to this old post we ended up gutting the bathroom as it needed doing and replacing everything. We have put a new triton shower in and had a plumber move the pipe work from under the floor to where it is accessible. Upon using the shower we are still getting intermittent hot and cold water. This doesn’t happen on any of the taps. This leads me to believe the problem has to be with the boiler.

 

[LGriffiths]

Could be a blocked plate heat exchanger causing the boiler to overheat and fire intermittently

 

[Ben-gee]

Are any of the other taps mixer taps, specifically ones where the hot/cold freely mix within the body as opposed to one’s where a divided flow is maintained until the end of the spout?

 

[ajt2018]

Are any of the other taps mixer taps, specifically ones where the hot/cold freely mix within the body as opposed to one’s where a divided flow is maintained until the end of the spout?

Hi, none of the taps in the house are mixer taps.

 

[Harvest Fields]

Is the new shower a bar mixer? Sorry if this has been asked not read all posts.

 

[Ben-gee]

If all hot taps are fine and only shower doesn’t work it doesn’t seem likely that the boiler is faulty.

Either faulty/ non-existent non return valves for shower?

Or flow through shower is not enough to keep boiler firing. This could be a number of reasons......

Blocked inlet filter to shower hot

Restrictors in shower supplies ( these often have to be removed for a Combi

“Eco flo” setting on shower , remove stop in flow handle.

Restrictive hose/head .....,

Or possibly new shower is faulty.

Get plumber to look at all of above ; if it’s a bar mixer it is trivial to swap it out for another known to be working one to eliminate boiler.

 

[ajt2018]

Is the new shower a bar mixer? Sorry if this has been asked not read all posts.

Hi, it’s a Tritan Verne mixer shower from screwfix. It slots onto the cold pipe and hot pipe which feed into the mixer.

 

[ajt2018]

If all hot taps are fine and only shower doesn’t work it doesn’t seem likely that the boiler is faulty.

Either faulty/ non-existent non return valves for shower?

Or flow through shower is not enough to keep boiler firing. This could be a number of reasons....

Blocked inlet filter to shower hot

Restrictors in shower supplies ( these often have to be removed for a Combi

“Eco flo” setting on shower , remove stop in flow handle.

Restrictive hose/head ...,

Or possibly new shower is faulty.

Get plumber to look at all of above ; if it’s a bar mixer it is trivial to swap it out for another known to be working one to eliminate boiler.

Hi, many thanks for the above reply appreciate everyone’s time and answers. I think will arrange for a plumber to look at it. Thanks

 

[Tea-Break]

Hi,
I would agree with Ben-gee. Very unlikely to be a boiler fault.
The length/size of the pipes could have an effect on both flow and temp.
Personally, I would have advised a good electric shower. Thus ensuring hot water for washing in the event of a boiler fault (combi).

 

[WHPES]

It sounds like the boiler is not able to keep up with the demand being placed on it by the hot water draw off for some reason, assuming you are meaing it goes from hot to cold and remains cold until water turned off, rather than cycling between hot and cold whilst running. If it were the heat exchanger then apart from the initial few seconds burst of hot water, it would never deliver hot water to the shower.

I suspect the shower remains hot if not turned on to full capacity. If so, a quick fix might be to change the shower head to an eco water saving version.

 

[ajt2018]

It sounds like the boiler is not able to keep up with the demand being placed on it by the hot water draw off for some reason, assuming you are meaing it goes from hot to cold and remains cold until water turned off, rather than cycling between hot and cold whilst running. If it were the heat exchanger then apart from the initial few seconds burst of hot water, it would never deliver hot water to the shower.

I suspect the shower remains hot if not turned on to full capacity. If so, a quick fix might be to change the shower head to an eco water saving version.

Hi, it alternates between hot and cold so it might warm up then stay hot for 30seconds to a 1 minute then it will gradually go cold for the same amount of time then go gradually hot again it’s like a rotation. We tested it again yesterday and it seems that it will stay consistently hot if you don’t touch the temperature gauge on the shower. But if the next person gets in who wants the temperature slightly lower and they turn the knob this then makes the shower then run hot and cold throughout the use of the shower for that period of time....

 

[Harvest Fields]

Sounds more like a cartridge/filter/non return issue.

 

[John.g]

Hi, it alternates between hot and cold so it might warm up then stay hot for 30seconds to a 1 minute then it will gradually go cold for the same amount of time then go gradually hot again it’s like a rotation. We tested it again yesterday and it seems that it will stay consistently hot if you don’t touch the temperature gauge on the shower. But if the next person gets in who wants the temperature slightly lower and they turn the knob this then makes the shower then run hot and cold throughout the use of the shower for that period of time..

Can you measure the flow rate from the shower when its "consistently hot" and then again when when running hot&cold, if the 15/19 boiler gives say ~ 17kw on hot water then you should get ~ 10 LPM at 40C .

 

[WHPES]

Does it stay the correct temperature if you run a hot tap slightly elsewhere to increase the demand? If so, I'd be looking at a flow switch fault