Plumbing Question - Shower not hot

LukeD · May 6, 2023

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 · May 6, 2023

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 · May 6, 2023

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 · May 6, 2023

Can you

mainline said:
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 · May 6, 2023

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 · May 6, 2023

brianmoooore said:
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 · May 6, 2023

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 · May 6, 2023

brianmoooore said:
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 · May 6, 2023

brianmoooore said:
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 · May 8, 2023

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 · May 8, 2023

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 · May 8, 2023

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?

[ElectriciansForums.net] Plumbing Question - Shower not hot

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 · May 8, 2023

brianmoooore said:
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