1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

Please help with my mixer shower- runs hot then cold

Discussion in 'Plumbing and Central Heating' started by heathertierney, 28 Feb 2010.

  1. heathertierney

    heathertierney

    Joined:
    28 Feb 2010
    Messages:
    4
    Thanks Received:
    0
    Location:
    Glasgow
    Country:
    United Kingdom
    Hi there,

    I am a complete plumbing novice but hopefully I can give you enough info to help me out.

    I live in a 3rd floor flat, I have a combi boiler (a vokera compact 24) and my shower is a mixer system (a previous plumber called it a Bristan).

    The shower runs hot then cold constantly, gradually changing from luke warm/cold to scalding every few seconds.

    I had a plumber out for a different issue and asked for his advise on the shower, he said that it was either the thermostat within the mixer unit which was faulty or it was because I have "mixed pressures". He advised running the hot tap whilst showering to see if that solved the problem. This hasn't helped.

    My question is does it sounds like I need to:

    A) buy a new mixer shower? - in which case can I just remove the existing unit from the wall and replace it with a new one or is it more complicated than that?

    B) would a new shower not fix the problem? In which case might it be something I can have looked at in the boiler? I read somewhere online about a similar problem being caused by a "fault heat exchanger".

    Any help would be much appreciated before I fork out money on a new shower/plumber to find out it has made on difference.

    Thank you in advance for your help.

    Kind regards,

    Heather
     
  2. Sponsored Links
  3. Agile

    Agile

    Joined:
    26 Jun 2004
    Messages:
    63,560
    Thanks Received:
    4,511
    Location:
    London
    Country:
    United Kingdom
    Your boiler has a different system to the ones you were reading about.

    It may be an interaction between the boiler and shower hence the suggestion of running a hot tap as well.

    Having mixed pressures is never a good idea and may be involved.

    Can you identify the hot water output pipe under the boiler and feel this while running the shower? See if it goes hot/cold as well.

    These can sometimes be difficult issues to resolve.

    Bristan is a very helpful UK based company and might have some suggestions or may send you a new mixer cartridge.

    You are so lucky you dont have a Triton as they are VERY unhelpful.

    Tony
     
  4. heathertierney

    heathertierney

    Joined:
    28 Feb 2010
    Messages:
    4
    Thanks Received:
    0
    Location:
    Glasgow
    Country:
    United Kingdom
    Thank you for getting back to me so quickly.

    I will try to find the hot water output pipe tonight when the shower is running and check that out.

    The plumber who mentioned the mixed pressures tried to illustrate it by running both taps and trying to stop the water flow by putting his finger into the tap, one tap stopped whilst the other was still shooting water out around his finger.

    If I do have mixed pressures is that difficult to resolve?

    I will put another post up once I have checked the hot water output pipe whilst the shower is running.

    Thanks again for your help.

    Kind regards,

    Heather
     
  5. kevindgas

    kevindgas

    Joined:
    28 Mar 2006
    Messages:
    5,743
    Thanks Received:
    478
    Location:
    Hedge End Hants
    Country:
    United Kingdom
    combi and mixer showers do not work together properly if the pressure is greater than the flow through the boiler.
    a pressure equalizing valve can be fitted to the shower supplies to create an equal pressure on the hot and cold.
     
  6. heathertierney

    heathertierney

    Joined:
    28 Feb 2010
    Messages:
    4
    Thanks Received:
    0
    Location:
    Glasgow
    Country:
    United Kingdom
    Right I checked the hot water output pipe which runs from the boiler through the wall to the bathroom. It seems to run hot (extremely hot) whilst the shower is running. I also tried it when the heaters were on and it was the same temperature, it didn't go hot/cold.

    Does that indicate that the boiler is working correctly?

    Thanks again, any advice is much appreciated.

    Heather :)
     
  7. Agile

    Agile

    Joined:
    26 Jun 2004
    Messages:
    63,560
    Thanks Received:
    4,511
    Location:
    London
    Country:
    United Kingdom
    That all depends if you had someone at the shower at the same time to confirm the shower was running hot/cold whilst the boiler output remains hot.

    The initial expectation is that the problem is primarily with the shower unit.

    Tony
     
  8. heathertierney

    heathertierney

    Joined:
    28 Feb 2010
    Messages:
    4
    Thanks Received:
    0
    Location:
    Glasgow
    Country:
    United Kingdom
    Yes I was touching the output water pipe under the boiler whilst my boyfriend ran the shower. The shower ran hot/cold while the boiler pipe was extremely hot.

    What sort of problem do you think I have?

    All help is very much appreciated!!

    Kind regards,

    Heather :)
     
  9. DIYnot Local

    DIYnot Local

    Joined:
    3 Sep 2019
    Country:
    United Kingdom

    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

    Select the supplier or trade you require, enter your location to begin your search.


    Are you a trade or supplier? You can create your listing free at DIYnot Local

     
  10. Sponsored Links
Loading...

Share This Page