Plumbing Question - Shower not hot

[brianmoooore]

The boilers you list are conventional , not combi rubbish, so it looks like you probably do have a gravity hot water system, fed from a tank in the loft. Hopefully, the cold water supply to the shower is also from the same tank.
The problem is almost certainly that the new shower has a higher minimum pressure requirement than the original.
It is becoming almost impossible to find taps, mixers, showers, etc. with really low minimum pressures since the rise of the combi boiler and a regulation change some years ago that replaced a minimum flow rate with so called water saving specification.
To make this work, I suspect a shower booster pump will have to be fitted.

 

[plugsandsparks]

There is the other think to check and thats the source of the hot and cold. Typically gravity fed shower mixers require that the cold supply also comes from the same header tank as the hot supply. Its possible that the mixer is not suitable for gravity supply and if the cold is coming directly from the mains it may be pushing past the mixer thus diluting the incoming hot even from the mixer is on full hot.
Suggest ask plumber whether mixer is even suitable for the install..

 

[LukeD]

YOu sure there is a Hot water tank in the loft ??

 

[Mark Wright]

Water tank in loft
Hot water tank upstairs
Boiler Kitchen
Shower down stairs.

 

[brianmoooore]

In that case, the 0.4 bar version may have been fitted. Can you determine the exact model?

 

[LukeD]

Here is a "tangent " to the debate ..... !! Ive seen the very reverse . And a child was badly injured .The water came from the shower at full temp causing the child to "throw itself through a shower door . NO matter what .There should be a "master " control that limits showers and taps in homes . I use valves to ensure when taps are open the volume of water entering a basin etc is not to much and sprays all over the place .But also to ensure that people dont get scalded .

 

[Mark Wright]

Thanks guys again for all your input.

Here is a link to the manual. If you can't download let me know
https://tinyurl.com/3p6un49r

Better upload https://tinyurl.com/49rfynrd

 

[mainline]

We still don’t know if this is gravity fed or not as it could be an unvented tank and the header tank could be for central heating.

Run a hot water tap and check if the header tank ball cock starts putting water in.
Then do the same with shower just using cold.

 

[LukeD]

Can you

We still don’t know if this is gravity fed or not as it could be an unvented tank and the header tank could be for central heating.

Run a hot water tap and check if the header tank ball cock starts putting water in.
Then do the same with shower just using cold.

exactly .....And God bless the King !

 

[brianmoooore]

The manual confirms you have the version with a min pressure of 0.4 bar, so it's odds on that this is the problem.
Manual also confirms that there are inlet filters (part #3).
The filter also incorporates check valves, which aren't needed if both hot and cold supplies come from the same header tank. Removing the hot one may solve the problem, to a degree, at least.

 

[Mark Wright]

The manual confirms you have the version with a min pressure of 0.4 bar, so it's odds on that this is the problem.
Manual also confirms that there are inlet filters (part #3).
The filter also incorporates check valves, which aren't needed if both hot and cold supplies come from the same header tank. Removing the hot one may solve the problem, to a degree, at least.

Isn't 0.4 very low already? Would I find a shower designed for even lower pressure. Also I should mention in the kitchen the Tap did need replacng cos it wasn't correct bar and just came out as a trickle when hot.

Pretty sure its gravity fed but ill do some investigating.

 

[brianmoooore]

Some years ago, I used to get promotional literature from the manufacturers along the lines of "our new tap/mixer/shower is the highest flowing on the market.
Cue the rise and influence of the tree huggers.
Now I get literature "our new tap/mixer/shower is the most economical and water saving on the market" which translates as "our new tap/mixer/shower is the lowest flowing on the market".
This is called progress.
Used to be no trouble finding stuff down to 0.1 bar, but these are few and far between nowadays. Still 0.2 bar stuff around, but even then it'll be a poor flow compared to what is considered normal these days. A double ended automatic shower pump is the usual solution.

 

[DPG]

Some years ago, I used to get promotional literature from the manufacturers along the lines of "our new tap/mixer/shower is the highest flowing on the market.
Cue the rise and influence of the tree huggers.
Now I get literature "our new tap/mixer/shower is the most economical and water saving on the market" which translates as "our new tap/mixer/shower is the lowest flowing on the market".
This is called progress.
Used to be no trouble finding stuff down to 0.1 bar, but these are few and far between nowadays. Still 0.2 bar stuff around, but even then it'll be a poor flow compared to what is considered normal these days. A double ended automatic shower pump is the usual solution.

I've had a few beers tonight with the Mrs, but full marks to Brian for knowledge of showers and BMWs!

 

[mainline]

The manual confirms you have the version with a min pressure of 0.4 bar, so it's odds on that this is the problem.
Manual also confirms that there are inlet filters (part #3).
The filter also incorporates check valves, which aren't needed if both hot and cold supplies come from the same header tank. Removing the hot one may solve the problem, to a degree, at least.

Only one degree that's not a lot

 

[Mark Wright]

Another note: I ignored this but she said the shower is hotter when the hot water is switched on at the programmer and yes it does seem to be. Again the hot tap a meter away is not affected as long as the hot water came on in the morning it has hot/boiling water but the shower having the hot water does make it better.
Any ideas?

 

[brianmoooore]

There's absolutely no point in doing so when a pump isn't involved, but the hot water for a shower is often taken from a slightly lower point in the cylinder than the rest of the hot water, to avoid problems with water being sucked down the cylinder vent pipe and air being drawn into the pump.
This arrangement leads to the hot water to the shower 'running out' a little before the hot water to the rest of the house, which would fit with the shower being a 'little better' with the boiler on.
A pic of the cylinder would confirm.
Are you sure that there isn't a shower pump somewhere, that may be switched off or otherwise not working for some reason?

 

[Mark Wright]

Thanks again for talking me through - Again I do feel this might have happened since the new boiler but I could be way off.

Is this what you want?



and do you know what this is> it's in a cupboard near the shower room?



If you want higher def pictures let me know.

 

[Avo Mk8]

Are you sure that there isn't a shower pump somewhere, that may be switched off or otherwise not working for some reason?

Looks like pump connections at the bottom of the pic?!

Mark Wright - would you mind taking a pic showing the flexi connections (to a pump?) down the bottom please?
And PS the 2nd pic is a programmable thermostat

https://www.underfloorheating-uk.co.uk/Cache/Downloads/devireg-User-guide.pdf

 

[Mark Wright]

Ok

Just so anyone knows I have nothing! to do with the wiring.

 

[Mark Wright]

This?