1/4 turn taps pain the backside

[diyguy123]

Are these taps prone to making the hot water run cold on a combi ? i have had to turn them back slightly from full to keep the water running hot.

i shower mostly but they are irritating when i do fancy a bath

can i just change the cartridges to full ones will these from toolstation work ?

this is what they have already.

Made4Trade Threaded Tap Glands 8mm spline With Threaded Collar | Toolstation

• Threaded tap glands to fit most 1/2" taps • 20 teeth on the spline • Code 55418 is suitable for taps that require a threaded collar

www.toolstation.com

 

[terryplumb]

Running hot taps at full flow will reduce hot water temperature ,changing the valves in the tap are not going to change that. Depending on your boiler ,if you have a dial to increase domestic hot water temperature ,you could turn that up higher when running a bath ,may allow increased flow and better temperature.

 

[diyguy123]

Running hot taps at full flow will reduce hot water temperature ,changing the valves in the tap are not going to change that. Depending on your boiler ,if you have a dial to increase domestic hot water temperature ,you could turn that up higher when running a bath ,may allow increased flow and better temperature.

The hot goes cold i have no idea why nowhere else has a problem.

 

[terryplumb]

Do you mean the tap gives hot water when turned on ,but then runs stone cold ,or just not as hot ?

 

[diyguy123]

Do you mean the tap gives hot water when turned on ,but then runs stone cold ,or just not as hot ?

yep runs cold unless you roll it back a bit

 

[terryplumb]

Can you turn up boiler tap water temp ,as suggested ?

 

[diyguy123]

Can you turn up boiler tap water temp ,as suggested ?

its not that as its been ok in the past, i changed them to full turn cartridges and the flow is much better but did not solve the issue.

i have a boiler plan and they have replaced the heat exchanger on the boiler the cheaper plate one, but tried to run a bath and it still goes cold after half full. will need to get them back again.

 

[Madrab]

The bath tap will be a much higher flow than your other sink/basin taps, by increasing the flow to the bath tap you have also increased the cold flow through your boiler and now your combi boiler can't keep up.

The combi is set to give a certain amount of flow @ L/Min at a 35deg rise (see the MI), if you exceed that flow through the boiler it then doesn't have a high enough KW input rating to raise the increased flow of cold water to the same levels, so the HW temp will decrease exponentially, especially in the winter when the mains cold water is anywhere up to 10deg cooler than in the summer.

 

[diyguy123]

The bath tap will be a much higher flow than your other sink/basin taps, by increasing the flow to the bath tap you have also increased the cold flow through your boiler and now your combi boiler can't keep up.

The combi is set to give a certain amount of flow @ L/Min at a 35deg rise (see the MI), if you exceed that flow through the boiler it then doesn't have a high enough KW input rating to raise the increased flow of cold water to the same levels, so the HW temp will decrease exponentially, especially in the winter when the mains cold water is anywhere up to 10deg cooler than in the summer.

true but this is a high flow combi boiler with a built in tank and it worked perfectly for 13 years prior.

 

[Madrab]

high flow combi boiler with a built in tank

Didn't have that key piece of info .... When running a bath it will be using up all the stored water, the boiler should then shift into combi mode. Either it's not keeping up as suggested or if it's cold cold then it may not even be switching into combi mode. What boiler is it?

 

[diyguy123]

Didn't have that key piece of info .... When running a bath it will be using up all the stored water, the boiler should then shift into combi mode. Either it's not keeping up as suggested or if it's cold cold then it may not even be switching into combi mode. What boiler is it?

It`s a Worcester 440 high flow. i would agree after the tank has been depleted it cannot seem to keep up i don't even put the water that hot at setting 2 52c to 54c. plate heat exchanger has already been changed i noticed the central heating is not getting as hot now either on setting 5 as it was before they changed it.

 

[Madrab]

They're usually pretty good even in combi mode, hence their high L/Min figures so it sounds like something isn't right.

 

[Johntheo5]

It`s a Worcester 440 high flow. i would agree after the tank has been depleted it cannot seem to keep up i don't even put the water that hot at setting 2 52c to 54c. plate heat exchanger has already been changed i noticed the central heating is not getting as hot now either on setting 5 as it was before they changed it.

Its easy enough to check your boiler output, once the stored water is used up then measure the "52C to 54C" DH water with a household thermometer, then run that water into a bucket for exactly 30secs and measure it with a 1 litre container or whatever, multipy this amount X 2 to give the flowrate in LPM. multipy this X 60 and X measured temperature minus 8.5 (my mains temperature just now, or measure your own mains temperature) and divide by 860.
So boiler output kw = (LPM X 60 X dT)/860.

 

[Madrab]

Alternatively you could just run the hot water at max rate once the boiler's in combi mode and gas rate the boiler.

Easy enough for a DIY'er to do - https://myboiler.com/calculators/gas-rate-calculator/

Then you could also run the combi mode HW into a weir gauge with a thermometer and check the temp at certain flow rates against the MI documented outputs/flow rates @ 35Deg rise.

That should give you proper comparisons between design and actual ... of course that's all moot if all it tells you is the boiler either is or isn't working properly, you would still need someone in to fix it.

 

[oilhead]

I've yet to see the combi that will deliver hot water to the bath through 3/4" taps ( and probably 22mm pipework) at anything above 1/3rd capacity. Just allow a little more time to fill your bath. If it has been running OK for some years, then you may have reached the point where the hot water heat exchanger has scaled up sufficiently to affect performance.