Freezing cold mixer shower :(

Kmodo

Kmodo

Kmodo

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2 Oct 2006
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  • Summer- run full speed with dial on max hot and it comes out pretty hot
  • Autumn- full speed with dial on max hot and it comes out warm
  • Autumn- half speed with dial on max hot and it comes out pretty hot
  • Winter- full speed with dial on max hot and it comes out freezing cold
  • Winter- half speed with dial on max hot and it comes out luke warm
  • Winter- quarter speed with dial on max hot and it comes out warmish

  • Mixer shower on wall in upstairs bathroom
  • Speed and Temperature dials
  • Combi boiler downstairs in kitchen
  • Turned the temperature up to max on the combi boiler made next to no difference

Last winter the same thing happened and this winter I am hoping to try and resolve it. My suspicion is that the cold water coming from the outside is freezing and there is not enough hot in the mixer to do anything about it.

So my question, if I take the mixer shower off of the wall, will there be something to turn that will increase the percentage of hot to cold water? Or could something inside it be degraded and need replacing?

Thanks!
 
Could be a number of things - sometimes the mixer cartridge scales up which can cause problems. Do you get full hot from your kitchen tap?

Is your cold water mains fed or from a loft tank? When you have you shower on does your boiler heat constantly or pulse on and off?
 
garak112 said:
Could be a number of things - sometimes the mixer cartridge scales up which can cause problems. Do you get full hot from your kitchen tap?

Is your cold water mains fed or from a loft tank? When you have you shower on does your boiler heat constantly or pulse on and off?
Click to expand...

Takes a few seconds but kitchen tap is full hot.
I can fill the bath with hot water. The hot water comes out at a constant temperature but it's not as hot as summer hot water (I'm thinking the water the combi boiler is heating up freezing cold water from mains and so does not get as hot as when it heats cold water in the summer time).

Cold water mains fed.

Don't know the answer to the last question over the weekend I'll find out.

So I could need a new mixer cartridge. Do you know if mixer cartridges are pretty generic?
 
Combi boilers have a maximum temperature rise so when the incoming water is colder it will have a lower maximum temperature.

Is it a thermostatic mixer?
 
garak112 said:
Combi boilers have a maximum temperature rise so when the incoming water is colder it will have a lower maximum temperature.

Is it a thermostatic mixer?
Click to expand...

Ahhh yeah that would make sense then.

In answer to the previous question the Mrs says the boiler is constantly running when the shower is going, not pulsing..

I bought the house about 4 years ago and the mixer shower was there before we moved in. I don't know if it is a thermostatic mixer, it looks pretty basic and from reading the description of one I'd say no, it's never been that advanced haha
 




Thought I'd upload a photo of it, it has BRISTAN written on the top.

So pretty sure it's not a thermostatic and is a basic mechanical.
If I take it off the wall on the weekend do you think I be able to decrease the amount of cold water getting mixed?
 
Those do have thermostatic valves in so that's most likely the problem. (Looking at about £50 for a replacement).
 
That is a decent mixer and as has been said, will be thermostatic.

Try and turn down the cold water pressure going into it. There should be a valve somewhere.
 
To me it sounds like your heat exchanger is to furred up with limescale and the heat is not getting to the water adequately! Resulting in you needing to change the speed of the incoming water to give it further chance to get to temperature. The outside water temp is exacerbating the issue.
 
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To test my theory, does the water temperature of the hot water taps all over the house reduce the faster you turn the tap on?

Reducing the cold water from the mixer in the shower will result in a pretty powerless shower as the hot water will be luke warm still.

Heat exchangers are easy to fix, and I don't think a engineer will charge a great deal.

Are you in the South of England by any chance.
 
ChroniC said:
To test my theory, does the water temperature of the hot water taps all over the house reduce the faster you turn the tap on?

Reducing the cold water from the mixer in the shower will result in a pretty powerless shower as the hot water will be luke warm still.

Heat exchangers are easy to fix, and I don't think a engineer will charge a great deal.

Are you in the South of England by any chance.
Click to expand...

Yes in the South West, south of Bristol and West of Bath. What you say about furred up with limescale is a good shout, if you touch the right of the mixer the metal is really hot!
 
Ahhh. Sorry tired and lacking in knowledge. Heat exchanger in the boiler with limescale?

All making sense, I think my radiators have not been as hot as well! Okay first job, sort boiler and then check the mixer as that might also have issues with limescale.

Both combined and then freezing cold outside water equals freezing shower in winter haha?!
 
I'm not an engineer by the way, so it's only a common assumption, it happens to boilers in the South particularly as it's a hard water area. That said I wouldn't want to think id made you pay out for a repair man on my advice, so take it at your own risk. :-D

If your taps seem to have decent pressure then maybe check the mixer first.
 
I have the same problem, and my shower is 2 months old. Same style mixer. I presumed the issue was due to outside water temp meaning that the boiler isn't able to heat the water to a decent level when being fed through the heat exchange. I have to run my shower at about 30% power to keep the flow rate at a level that gives the boiler enough time to heat it. Fully on and the water isn't that hot.
 
Kmodo said:
Yes in the South West, south of Bristol and West of Bath. What you say about furred up with limescale is a good shout, if you touch the right of the mixer the metal is really hot!
Click to expand...

If the hot water part of the mixer is getting really hot and your other taps are putting out water that is also hot then the fault is more likely to be in the thermostatic tap cartridge than the heat exchanger, otherwise you would have poor heat from all your taps (especially the kitchen one which is likely to have the highest flow).
 
I have a very similar mixer shower by Bristan and encountered the exact same problem.

The cause was a combination of the cartridge scaling up/needing greasing and a poor design which means the cartridge struggles to fully open due to the finish of the internal chassis not being great.

I followed the instructions in the manual:

If the cartridge is heavily covered in lime scale, we suggest submerging it in a 50/50 solution of hot water and white vinegar. Leave the cartridge to soak for approximately 4 hours, take out and rinse the solution off with cold water

8. Apply silicon grease (sp-495-0002) with clean hands around all visible black seals as shown opposite, and avoid contact with foreign objects to keep it clean until refitted. Insert the cartridge back into the bar shower valve
Click to expand...

I then also didn't do the cartridge up quite as tight, leaving it half a turn undone making it easier for the mechanism to move to let hot water through but secure enough to not let water out when closed or come undone.

Works a dream now.
 
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garak112 said:
If the hot water part of the mixer is getting really hot and your other taps are putting out water that is also hot then the fault is more likely to be in the thermostatic tap cartridge than the heat exchanger, otherwise you would have poor heat from all your taps (especially the kitchen one which is likely to have the highest flow).
Click to expand...


Abyss said:
I have a very similar mixer shower by Bristan and encountered the exact same problem.

The cause was a combination of the cartridge scaling up/needing greasing and a poor design which means the cartridge struggles to fully open due to the finish of the internal chassis not being great.

I followed the instructions in the manual:



I then also didn't do the cartridge up quite as tight, leaving it half a turn undone making it easier for the mechanism to move to let hot water through but secure enough to not let water out when closed or come undone.

Works a dream now.
Click to expand...


We have a three month old so have a baby bath thermometer.

I decided to use it to test the temperature of the water.

Bathroom
Bath hotwater tap = 38degrees
Sink hotwater tap = 38degrees

Kitchen
Kitchen sink hotwater tap = 44degrees

Is it quite common for a 6 degree temperature difference from downstairs to upstairs?

Either way, I think from the posts it seems like it is pointing back at the mixer shower as a definite issue. It would be a dream to shower in something closer to 38degrees!

I will get that sorted first and then look into the boiler when I have more money :)
 
It's the mixer for sure, I have 2x the same shower units and both have gone. One is stuck in position right now (lucky to the hot position!).
 
Cheers guys I replaced the cartridge and now my shower is nice and hot, even has steam haha!

Although my shower was clearly at fault, during the troubleshooting phase I realised that my hot water is not good enough. Even the Bristan mixer instructions says minimum recommended 50 degrees input from the hot and as my previous posts have mentioned I have 38 degrees in the bathroom.

I've got a powerflush guy (lots of good reviews on checkatrade) coming round next week so hopefully that coupled with changing the heat exchanger will sort out my general boiler on max but hot water not that hot issues :)
 
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