Lower Temp From Bath Tap.

MarkeR · 5 Dec 2019 at 09:07

Bit of a strange situation here.
I have turned my water temp up to max on my boiler, the water temp from the taps in the house all run at the same temp apart from the bath tap.
As a test I put the water to maximum, which would actually scold you if you left your hand under for too long, the bath tap runs comfortably hot.
Is there such a thing as not enough water pressure release fromn the tap to initiate the hot water from the boiler?
I cannot think of any reason why the temps would be so different.

Thanks

Burned_Alive · 5 Dec 2019 at 09:20

It will have a thermostatic mixing valve on it which is preventing the water being too hot by feeding cold water in. It will be situated behind the bath panel most likely.

Is this a new build?

MarkeR · 5 Dec 2019 at 09:32

New bathroom fitted recently.

Trying to get hold of the fitter, but as per they are slightly tardy in returning calls. I still havent paid in full so I have that ging for me.

If there is a valve fitted, can that be removed? I understand why it is there, but I would like my own choice of water temp!

Thanks

FNG · 5 Dec 2019 at 10:07

If you are on a combi system and the tap is a high flow tap it may be that the boiler can not heat it to the higher temperature. Try running it slower and seeing if it gets hotter, that will atleast show that this is the problem.

Semple · 5 Dec 2019 at 11:08

FNG said:
If you are on a combi system and the tap is a high flow tap it may be that the boiler can not heat it to the higher temperature. Try running it slower and seeing if it gets hotter, that will atleast show that this is the problem.

Yep would recommend trying this. Our water flow rate is actually rather good, but if you max out the hot tap the combi boiler struggles to keep up and will then only throw out warm water. Reducing the flow allows the boiler to fully heat all that water.

MarkeR · 5 Dec 2019 at 12:05

FNG said:
If you are on a combi system and the tap is a high flow tap it may be that the boiler can not heat it to the higher temperature. Try running it slower and seeing if it gets hotter, that will atleast show that this is the problem.

Actually tried this before i saw your post, and this is exactly what is happening. Turned the flow down to around 1/3 and the water is at the correct temp..

Thanks guys

a1ex2001 · 6 Dec 2019 at 02:16

MarkeR said:
Actually tried this before i saw your post, and this is exactly what is happening. Turned the flow down to around 1/3 and the water is at the correct temp..

Thanks guys

Always much worse at this time of year as the in coming water is so cold!

2004typer · 6 Dec 2019 at 08:39

It will be a thermostatic valve - presumably the plumber has fitted one by default - they are usually set to 48 degrees maximum.

The question above r.e. the new build was relevant in that Approved Doc. G in the Building Regs. requires these to be fitted in new dwellings to prevent persons running a scolding hot bath - I believe there have been instances where people have died from immersing themselves in water that is too hot, hence this regulation is an attempt to try and prevent this.

dirtychinchilla · 6 Dec 2019 at 12:20

Can I just say that you probably don't need a temp of higher than 50C. You'll just end up mixing it down at the tap and then you've wasted a load of energy heating it up above 50C.

james.miller · 6 Dec 2019 at 12:41

dirtychinchilla said:
Can I just say that you probably don't need a temp of higher than 50C. You'll just end up mixing it down at the tap and then you've wasted a load of energy heating it up above 50C.

you risk the chance of legionnaires' if you don't heat your water up to above 50c. 55c is probably the minimum.

dirtychinchilla · 6 Dec 2019 at 13:19

james.miller said:
you risk the chance of legionnaires' if you don't heat your water up to above 50c. 55c is probably the minimum.

Only if you're storing water i.e. have a hot water tank.

james.miller · 6 Dec 2019 at 13:31

even if you have a combi there is still a risk of bacteria growing in the hot water pipes. Turning the hot water temp down to 50c or below will promote that. It's not worth the risk, IMO.

Abyss · 6 Dec 2019 at 13:47

dirtychinchilla said:
Can I just say that you probably don't need a temp of higher than 50C. You'll just end up mixing it down at the tap and then you've wasted a load of energy heating it up above 50C.

Definitely sounds like a thermostatic mixing valve.
Great idea until you're already in the bath and want to top it up as it's going cold but have to refill half the bath to get it to 38 degrees.

I've set ours at around 55 degrees so no risk of scalding from putting hand under the tap (unless you hold it there for 30 seconds plus) but hot enough to top up a bath.

fadetoblack · 10 Dec 2019 at 17:39

Little test to see if a a TMV is fitted turn the cold water feed off at the boiler. And run the hot water on the bath if a tmv is fitted the hot water will shut off as a safety measure (thermal shutdown)

b0rn2sk8 · 10 Dec 2019 at 20:53

Why are people still posting here.....?

FNG said:
If you are on a combi system and the tap is a high flow tap it may be that the boiler can not heat it to the higher temperature. Try running it slower and seeing if it gets hotter, that will atleast show that this is the problem.

MarkeR said:
Actually tried this before i saw your post, and this is exactly what is happening. Turned the flow down to around 1/3 and the water is at the correct temp..

Thanks guys

fadetoblack · 11 Dec 2019 at 05:31

b0rn2sk8 said:
Why are people still posting here.....?

Maybe because it’s a forum

b0rn2sk8 · 11 Dec 2019 at 08:16

It would be a good point if people actually read the thread before posting.

james.miller · 11 Dec 2019 at 08:26

Clearly, the discussion wasn't done. Anyway, If you want the thread to die then stop posting in it?

Orionaut · 11 Dec 2019 at 14:18

MarkeR said:
Actually tried this before i saw your post, and this is exactly what is happening. Turned the flow down to around 1/3 and the water is at the correct temp..

Thanks guys

This is sort of back to the future, 1960's (even 1980's)

Juggling the water flow through the geyser was a routine thing back in bedsit land days, As was being careful not to actually gas oneself since the geysers were frequently unvented!

rubberduck · 13 Dec 2019 at 01:12

james.miller said:
you risk the chance of legionnaires' if you don't heat your water up to above 50c. 55c is probably the minimum.

This seems absurdly far fetched that you could get legionnaires in such manner from running a bath via a combi boiler. Do the bacteria have time to proliferate in any significant way in the time from when the water goes above 20 degrees in the combi to when the water goes down the plug say 30 minutes later? I suspect surfactant based products I.e soaps and shampoos would further hamper the bacteria in getting a foothold.