Problem with hot water to bath

[Katie McMillan]

I have hot water going to the kitchen sink (downstairs) and hot water going to the bathroom sink (upstairs). Both are flowing well, nice and hot.
However...The hot water to the bath, when the hot tap is fully switched on, is coming out barely tepid. If the hot tap is partially closed, the water will run at the correct temperature. The type of tap is a dual flow mixer tap (I think), i.e. one stream of water, but both hot and cold taps can be turned on at the same time.
The boiler is a Potterton and was fitted 3 1/2 years ago. No faults showing on the boiler and the central heating system is working fine. The problem has only developed in the past few days. No problems previously. Thanks for any advice.

 

[Chalked]

Is it a combi boiler?

 

[Katie McMillan]

Hi,

Yes, it is a combi boiler. A Potterton Promax Combi HE Plus A Range.

Thanks

 

[jtsplumbing]

In some cases your better to fit new bath taps ! depends if the ones you have are expensive or just your average bath mixer, surprising how much time can be wasted just finding the correct part for your tap, sometimes just more cost effective to replace

 

[Katie McMillan]

Thank you for your reply.

Do you think then that the problem is likely to lie with the tap itself as opposed to a more technical problem with the boiler or pipes etc?

 

[jtsplumbing]

Thank you for your reply.

Do you think then that the problem is likely to lie with the tap itself as opposed to a more technical problem with the boiler or pipes etc?

If hot water is ok at other taps !! the fault is with the bath Tap NOT the boiler

 

[gassafe]

Normal operation for a combi & this time of year, flow rate is too fast & the boiler can't keep up... You said yourself the Tap gets hot when flow is reduced!

 

[Katie McMillan]

Thank you for your reply.

Would you suggest then that no action is required? The other taps are working fine, they do not need to be partially closed for hot water to flow. Having to partially close the hot tap is creating a real inconvenience for the tenant.

 

[Katie McMillan]

Thank you,

Is it a particularly big job to replace the tap? What would you estimate the approximate cost for a plumber to do this?

 

[gassafe]

Thank you,

Is it a particularly big job to replace the tap? What would you estimate the approximate cost for a plumber to do this?

Change it if you want. The new tap will do the same tho

 

[gassafe]

Thank you for your reply.

Having to partially close the hot tap is creating a real inconvenience for the tenant.

Really?

 

[Katie McMillan]

Hi gassafe,

It's causing an inconvenience because it's taking nearly 1/2 an hour to get enough hot water into the bath to have a half full bath!

Usually the bath would be full, hot and good to go within about 8 or 9 minutes. It just seems strange to me that a few days ago (and since the boiler was fitted 3 years ago) everything was working as it should be, and now it's not.

I understand what you're saying about the time of year and perhaps the cold weather having an effect, but the bath is situated in the North of Scotland where outside temperatures are usually very cold for at least 6 months of the year and this has never happened before. I was just worried that there might be something wrong with the boiler or perhaps the taps.

Thanks for your replies so far, it is appreciated.

Katie.

 

[stevetheplumber]

i suggest you find out the flow rate of your boiler and test the flow rate on the bath im sure you will find the tap is running to fast when fully open

 

[Masood]

Got to agree with gassafe and Steve here. Unless it's a thermostatic mixer (very unusual on a bath tap) then unlikely to be the tap.

Here's a way of checking:

Get a 1 litre measuring jug. Time how long it takes to fill it at the kitchen or basin tap (wherever the water is coming out hot). Then adjust the bath tap flow so you get the same litre per minute rate. Compare temperatures. That'll answer the question once and for all.

 

[gasmanrob]

run basin tap in the bathroom untill hot and steady temperature then half open the bath tap to where it has been needed to have it hot monitor both bath and basin temps.

both move to tepid excessive flow rate not aided by lower incoming mains temperature.

basin hot bath tepid... faulty mixer or similar and investigation required

 

[Unregistered]

Thank you to everyone for your replies. I will try out the suggestions tomorrow. It's great to be able to ask a question of experienced tradespeople and get helpful advice. Merry Christmas to all.

 

[Allgoode]

Hi,

If you check the diameter of the pipe to the basin and the one's to the bath taps you will probably find a large difference.

Generally you have 15mm to basin taps & 22mm to the bath taps thus the bath taps can deliver a far greater flow than the boiler spec flow rate can cope with at a set temp rise.

For the bath one option is to get some Calflow plus flow regulator with appropriate flow cartridge, this will restrict the maximum flow to the preset flow rate no matter if the bath tap is fully opened.

Also you may find if you have mono basin/sink taps they will be fed through flexi pipe connectors which again are a smaller internal diameter which restrict flow rates but means the water coming out of them is hot.

The boiler specs for the range vary between 9.8 litres per min & 13.5 litres per min at a 35 degree rise.

What this means to someone is if the incoming water is 15degrees during the summer you could reasonably expect it to be 50 degrees at the tap at the above flow rates depending on boiler model.

If as now during the winter the incoming mains is down to say 7 degrees then with the 35 degree temp rise at above flow rates the water will feel noticeably cooler but the boiler will be working within manufacturers specs.

Also you did not say whether the boiler has been recently serviced.

I carried out a service on an older halstead eden cbx 32 boiler recently which had been maintained by British Gas for the previous 7 years and the hot water temps and flow rate where poor.

Post a full service and clean iaw the manufacturers instructions the customer could not believe the difference it made to the temperature and flow rate so you may find that the boiler may be in need of a good service & clean.

Hope this helps,

Andy

 

[dean.diy]

after going through all the posts it seems someone might have had a fiddle.Does happen in rented.

 

[zzzjim]

Change it if you want. The new tap will do the same tho

Or Run slower than the old one and be nice and hot ..like requested

Science / Physics - Cannot be beaten !

 

[SimonG]

Fit restrictor under bath to get the flow right for hot water.

 

[dean.diy]

might already be an iso there , turned the wrong way and left in a panic when it started weeping.