Does hot/cold pressure imbalance affect my mixer shower temp?

[HarryHarris]

I have a combi boiler (Vailant ecoplus) and a mixer bar shower. The taps in the rest of the house, including bathroom, get super hot on demand. The pipe behind the mixer shower are very hot to the touch and yet even woth the thermo valve on the mixer at full it is moderately hot at best.

Ive tried taking the head of the thermo valve on the mixer and adjusting the limiter to its max but it seems like its already there.

The guy on the shower provider 'live chat' told me this is an issue of my hot water pressure not matching my cold water pressure. Is this likely? and if so, is there a way for me to adjust these pressures or do I need to call a professional?

(NB sometimes the shower is totally fine and gets up to a good temp, but still has to be on max temp for this, and other times its barely warm. Most of the time its somewhere inbetween. It seems to fluctuate every time)

Thanks for any help or advise.

 

[ShaunCorbs]

how old is the shower/ bart mixer?

sounds like the cartridge is starting to go (regulates how and cold temps)

 

[HarryHarris]

how old is the shower/ bart mixer?

sounds like the cartridge is starting to go (regulates how and cold temps)

Its brand new. Only fitted it a couple of weeks ago.

 

[steadyon]

1. With a combi boiler, hot and cold pressures will be identical to within a very small percentage, unless you have a very unusual setup.
2. If it was fitted professionally, the installer should have set the output temperature as part of the installation. Normally set to maximum 38 degrees unless the customer asks for something different.
3. Are you sure the hot and cold connections are the right way round?
4. What mixer shower is it?

 

[Plumbstar Tom]

you will find it is the flow rates, the combi will be slowing the hot water flow down in order to heat it. The shower should have had flow limiters on the inlets fitted, but it sounds like there weren't

Can you check the fitting instructions for the shower? What make and model is it?

 

[HarryHarris]

Its a Larkin Bar Shower mixer from Betterbathrooms.

betterbathrooms.com/showers/shower-valves/larkin-bar-shower-valve/

I fitted the shower myself, replacing the old mixer bar on the existing inlets. Should I have added flow limiters to the inlets? I made sure I bought a mixer labelled as suitable for combi boilers and low pressure systems.

Ive tiled over the plumbing behind the wall where the shower is now, so getting access to the pipes again is going to require a bit of smashing. Thanks for your help

 

[HarryHarris]

I only bought the house a few months ago, boiler seems ok generally, all other rads and taps get plenty hot, but I have no idea who fitted it. (The old house owner was a bit of a cowboy by the state of his other electrics/plumbing so I wouldn't be surprised if he fitted it himself)

I'm sure the hot/cold is the right way round.

its a larkin bar mixer.

Thanks

 

[Plumbstar Tom]

try turning a few taps on and then the shower at its hottest setting. any good then?

 

[HarryHarris]

Yes Tom, just tried it, the shower was luke warm,but when I turned the cold taps on in the bathroom it got much hotter. Assuming this is a cold water pressure issue then?

I still dont understand why the thermo valve in the mixer cant be adjustable to allow more hot water and less cold through, like the mixer on my taps? Do they set an upper limit of say 80%Hot 20%cold even at max temp. I would expect when I turn the valve fully I would get 100%Hot 0%Cold.

 

[ShaunCorbs]

does the boiler fire just with the shower running?

 

[Plumbstar Tom]

No, thermostatic always mixes water, no matter what setting. You will ideally need flow limiters in there to sort the issue. To be honest decent manufacturers normally put them in the box.

You might be able to use something like this:

https://www.bes.co.uk/shower-flow-l...-Syy9hJz9i-I8WVMvOCFwOeqKfcTfGRmnuRoCa5rw_wcB

 

[HarryHarris]

does the boiler fire just with the shower running?

yes

 

[HarryHarris]

No, thermostatic always mixes water, no matter what setting. You will ideally need flow limiters in there to sort the issue. To be honest decent manufacturers normally put them in the box.

You might be able to use something like this:

https://www.bes.co.uk/shower-flow-l...-Syy9hJz9i-I8WVMvOCFwOeqKfcTfGRmnuRoCa5rw_wcB

Thanks Tom, I'll try something like that. Fingers crossed.

 

[HarryHarris]

Just to be clear. Do i need to put the limiter on the cold inlet before the thermostatic mixer valve? Or just generally reduce flow overall by putting it after the mixer on the hose outlet?

Thanks

 

[Chalked]

You need to fit the flow limiter to the cold inlet.