Shower suddenly hot when downstairs toilet flushes

[kofi2003uk]

Hi Everyone
I have had this problem since moving into this property and I will like to fix it and need some advice please
The shower in the en-suite bathroom upstairs is nice to use until someone flushes the downstairs toilet. It gets suddenly too hot. I guess the cold water in en-suite bathroom and downstairs toilet use same cold feed pipe.
Clearly the downstairs toilet refilling takes the pressure and literally steals the cold water from the upstairs shower until toilet refills.
My question is how do I fix this and what are my options in fixing this issue please?

I will get a plumber in if I have to as it’s dangerous but will be nice to know the options available.

Thank you all

 

[JohnD]

Have you got a combi boiler?

Is it an electric shower?

Please post a photo of your shower mixer.

How old is the house?

 

[kofi2003uk]

Thanks for the reply. I have a hot water cylinder- unvented. Plus vaillant 418 boiler. No conbi. House was only built in 1999. Thank you

 

[JohnD]

Please post a photo of your shower mixer.

 

[Hugh Jaleak]

Firstly need to know what type of shower you have in order to best advise. Clearly the issue presents when cold water is drawn off elsewhere in the property, but until we know the setup it's impossible to say what might need doing.

 

[kofi2003uk]

Just posted a picture of shower. Thank you both. Yes issue is only when downstairs toilet flushes. Or as Hugh says, when water is drawn somewhere else but I think it’s mainly when downstairs toilet is flushed. Thanks

 

[JohnD]

Looks like the supply pipes are buried in the wall. Are they both accessible anywhere nearby, such as the airing cupboard or ceiling?

 

[Harry Bloomfield]

The shower in the en-suite bathroom upstairs is nice to use until someone flushes the downstairs toilet. It gets suddenly too hot. I guess the cold water in en-suite bathroom and downstairs toilet use same cold feed pipe.
Clearly the downstairs toilet refilling takes the pressure and literally steals the cold water from the upstairs shower until toilet refills.
My question is how do I fix this and what are my options in fixing this issue please?

It reads as if your HW comes under low pressure from the HW cylinder and the cold it mixes with, is from the mains. The easy fix, is to ban anyone from using the cold water/flushing, whilst anyone is using the shower. More involved, you could perhaps have the cold feed to the shower, diverted to run from the cold water header tank in the loft.

 

[JohnD]

It reads as if your HW comes under low pressure from the HW cylinder

He said it is an unvented cylinder. Do you think that might not be true?

@kofi2003uk what colour is it? Please post photos.

 

[Harry Bloomfield]

He said it is an unvented cylinder. Do you think that might not be true?

@kofi2003uk what colour is it? Please post photos.

OK, I didn't spot the OP's later post..

 

[kofi2003uk]

Correct the supply pipes are buried as JohnD puts it. It will be a big and very costly job to change any pipes.
Planning on renovating the bathroom next summer. May have to get some sort of thermostatic valve installed behind the new shower?

 

[kofi2003uk]

Yea unvented. No cold water tank. Previously had a cold water tank in loft but that was replaced with the unvented cylinder in airing cupboard just behind the en-suite bathroom actually. Thx

 

[kofi2003uk]

Pipes are hidden behind wall. Plaster boards as you find in recent builds but will be major work and very costly if I start taking walls down. Hopefully there is a way without making it a ‘big job’
Thanks

 

[Johntheo5]

Why don't you install a valve on the toilet supply and just throttle it, you don't require the toilet cistern to fill very rapidly?

 

[kofi2003uk]

Why don't you install a valve on the toilet supply and just throttle it, you don't require the toilet cistern to fill very rapidly?

Thought about that actually. Only issue is there is no visible pipe to stick the valve on. Toilet is the type that sits flashed to the wall from floor so pipe must be hidden behind . I guess that’s an option if I have no other simple options. Remove toilet, add valve behind it and turn flow down. Might not fix it completely but will reduce the amount of cold water being taken from shower.