Hot water problems -boiling kitchen, luke warm bathroom

[Lusi83]

Can anyone explain this to me
Worchester Bosch 35CDII combi boiler - about 10 years old.
Had a few bits replaced in last year....(including a valve to heat exchanger (IIRC) and external expansion vessel)- settings will have been changed - I think maybe water feed pressure increased (we have v high water pressure, have it turned down on stop cock and think it used to not be turned fully on into boiler) - sure it didn't used to be like this....
In Kitchen hot water gets really hot -too hot to bear...(although has had a new cartridge on this tap too...)
In bathroom doesn't need any cold when running a bath...never gets very hot. Just tried to fill a jug of hot water in bathroom and must have run gallons of water ...never got above lukewarm and then went cold.
Boiler is upstairs probably about the same distance from bathroom as kitchen...both (I think) feed to and then from where hot water tank used to be when old boiler was in.
I think feed to kitchen is 22 mm - whereas to bathroom is 15 mm ...
Any ideas?

 

[Breesey]

The kitchen tap is probably 15mm and the bath tap 22mm. The boiler can't heat the amount of water flowing through the boiler to the bath as it can to the kitchen, particularly as the incoming water temp is lower in this weather.

Opening the bath tap less may improve the water temp.

 

[JohnD]

Is the basin tap lukewarm, or only the bath?

Typical combi.

Fill a bucket at the hot bath tap, time it, calculate how many litres per minute it delivers. Too many, I bet.

 

[Lusi83]

I keep trying to get it warmer by reducing the flow upstairs but it seems to then not to be enough to get it to fire up - so it goes cold - the jug was in the bathroom basin - so 15mmm taps....
(actually kitchen tap seems to run fast enough ...but know that isn't fully turned on at its isolator valve)

 

[Lusi83]

Sorry cross post ...what do you mean that the water pressure is too high for the combi?
(I know it was the highest lt per min hot water I could get at the time - so 12 or 15Lt????)
I can't do a bucket now - might wake children up ...but can try tomorrow - do I turn the taps fully on?

 

[Breesey]

It'll only raise about 12l/min by about 35 degrees.

What you need to know is what about 8l/min looks like!!

 

[JohnD]

Yes you turn the taps fully on to measure maximum flow.

Flow is not the same as pressure.

 

[Lusi83]

Ok - that was a bit of faff ...(first attempt bucket overflowed!)
Did it for 30 secs and got just less than 8lt - so approx 16 lt/per min (maybe slightly more than that - coordinating tap, timer and bucket probably lost a second or so at start)
I never turn tap full on to run bath - usually about 3/4 -(12Lt/per min -lukewarm) so can see why bath is not very hot now...
Feed to kitchen is actually 15mm too ( looked at pipes again - think 22 mm is cold feed upstairs)

(also did basin and Kitchen sink - but just for 15 secs - works out at 16Lt/min for bathroom and a bit less for kitchen -but that could just be difference in my reaction times!)
Other thing I noticed is I must really never turn kitchen tap on full blast - (splashes everywhere)...

 

[gas112]

if sink and basin are ok and you are throttling bath tap down to 12l a min and its still luke warm you may possibly have a faulty mixer tap on the bath and its pulling cold in with the hot

 

[Lusi83]

Thanks but unfortunately it is the bathroom basin too ....that was where I was trying to get a jug of hot water from!

We have a separate shower in the bathroom which is a thermostat one (Mira) but isn't designed for a combi. At first the heating engineers who put the central heating in (combi from HW tank) told me it was dangerous to use and I needed a new shower but later fitted two taps to the feed pipes to adjust the hot and cold flow (these aren't turned fully one and marked how many turns etc). That seems still to be working fine...(unless the thermostat evens it out or something)...

 

[Lusi83]

Sorry... children easter hols distraction...but still could do with sorting this out ...
Thinking about this....if I turn the rate at which the water flows into the boiler down for the hot water...
Then turn the isolator on the kitchen tap up ..and the ones on the bath and basin maybe leave or if nec turn down ...will that even it out?

(Suspect the shower is ok cos it has a thermostat on it...)

Thanks for any help....

 

[picasso]

Isolate the shower completely if you can and see if all the hot taps run at the same temp.

 

[TCCHeating]

Isolate the cold water inlet to the boiler, if you then get water flowing through the hot taps then something is passing from cold to hot, showers are norotious for this

 

[Lusi83]

I will try both ....
I don't think it is cold getting into hot in the pipes ...when heating was installed and hot water went onto mains pressure the hot water plastic pipes in the bathroom failed at the joints - flew off spraying water everywhere - we had the hot water off at the boiler until we could get (most) of the pipes replaced with copper...and it is a pretty recent problem -
Unless the plumber who fixed the leak on the boiler managed to do something inside the boiler...

 

[TCCHeating]

I will try both ....
I don't think it is cold getting into hot in the pipes ...when heating was installed and hot water went onto mains pressure the hot water plastic pipes in the bathroom failed at the joints - flew off spraying water everywhere - we had the hot water off at the boiler until we could get (most) of the pipes replaced with copper...and it is a pretty recent problem -
Unless the plumber who fixed the leak on the boiler managed to do something inside the boiler...

what i was talking about is nothing to do with boiler or pipework, probs like this can occur if the shower valve is passing, quite common on thermostatic mixers.