Plumbing Question - Shower not hot

Discuss Plumbing Question - Shower not hot in the Central Heating Systems area at ElectriciansForums.net

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.
Click to expand...
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.
 
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.
 
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.
Click to expand...

I've had a few beers tonight with the Mrs, but full marks to Brian for knowledge of showers and BMWs!
 
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.
Click to expand...
Only one degree that's not a lot :)
 
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?
 
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?
 
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?

1.png

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

2.png

If you want higher def pictures let me know.
 
Last edited:
Its a temp controller for underfloor heating systems. But can still be used
Mark Wright said:
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?

View attachment 107969

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

View attachment 107970

If you want higher def pictures let me know.
Click to expand...
temp control unit designed for underfloor systems .But its fine
 
ill have a feel of those flexi pipes and see if they get hot?

I think that pump was fitted/replaced when the boiler was. So if the pump comes on with the shower and not the tap - the shower is fed from a different source?
 
Last edited:
The feed for the shower hot does come from a special fitting that draws the water from slightly down the cylinder, and that is most definitely a shower pump on the end of the pipe that feeds from it.
Follow the flex from the pump to where it connects to a FCU, and see if it is switched on.
Also, check that the gate valve with the red wheel handle, near the top of the cylinder is fully turned on.
 
Last edited:
brianmoooore said:
The feed for the shower hot does come from a special fitting that draws the water from slightly down the cylinder, and that is most definitely a shower pump on the end of the pipe that feeds from it.
Follow the flex from the pump to where it connects to a FCU, and see if it is switched on.
Also, check that the gate valve with the red wheel handle, near the top of the cylinder is fully turned on.
Click to expand...
Hi yes the pump comes on with the shower. I posted a video above but it's probably not showing :(

With the shower running the two flexi pipes at the front of the pump are warm but not hot
4.png
 
The gate valve is open full - I closed it to see what would happen and it was still slightly warm? maybe cos the pipes were warm.

So I'm guessing something is not right with the feed to the pump. But cant understand why the tap is hot because it's from the same tank.
 
The immersion heater would normally be switched off. It's only there to a) block up the big hole in the cylinder, and b) as an emergency backup if the boiler is out of order.
The problem with the shower is definitely the non working of the shower pump. Everything that has been discussed before is now irrelevant.
Do you have a non contact voltage detector (Volt Stick)? If so, wave it around the pump cable to see if it is live.
 
brianmoooore said:
The immersion heater would normally be switched off. It's only there to a) block up the big hole in the cylinder, and b) as an emergency backup if the boiler is out of order.
The problem with the shower is definitely the non working of the shower pump. Everything that has been discussed before is now irrelevant.
Do you have a non contact voltage detector (Volt Stick)? If so, wave it around the pump cable to see if it is live.
Click to expand...
The OP said that the pump comes on with the shower #66
 
Ah, so that's what that short video was about. Doesn't come over very well on a laptop without sound. Listened to it on my phone now, and it doesn't sound very happy, but having been asked many times to diagnose car faults from videos, I know that's the norm.
The black connectors at the top of the pump flexible pipes often have quarter turn isolator valves built into them. If they are present, are they all fully on?
I've also come across pumps where there are little mesh filters built into the rubber washers between the nuts at the bottom of the flexible pipes and the pump.
All comments about the shower valve having a to high minimum pressure requirement are now invalid. Something's blocking the hot water flow.
 
Knob position needs to be sorted ASAP, then. That's why I said to mark the original position of the shaft.
Stored water temp. should be near enough the same whether heated by the immersion heater or the boiler. There's a thermostat under the cover of the immersion heater (electricity OFF), which may be marked in degrees, although they haven't been calibrated for many years. If it's an uncalibrated one it left the factory with the dial locked in place by a blob of sealant. Check for it having been 'got at', or it could just have gone wrong of course. if it has a calibrated dial, it should be set at 65 degrees.
The hot water temp, if the water is heated by the boiler, is set by the thermostat that can be seen strapped to the front of the cylinder. This should be set to 65 degrees as well. Can just make out the knob position in the pic, and it doesn't look far out.
The boiler flow temp. must be set slightly higher than the 'stat on the cylinder, otherwise the boiler will cycle on and off after the cylinder is 'full'. I suspect many boilers now suffer from this problem, following the misinformation put out by the government green brigade.
 
Not much to go wrong with them, other than build up of scale.
First priority is to work out why there's a big difference in hot water temperature between that heated by the immersion and that heated by the boiler.
It would be interesting to disconnect the feed to the hot water side (at the front in the pic.) and see if you get a decent flow there.
Check than 'in' and 'out' are the right way around on the pump. Ignore that. I can see they are correct in one of the pics.
 
Still so puzzled -
The tap gets hot
The shower doesn't
The hot water from the Shower goes through the pump
But both come from the same source
The flexible cables entering the pump aren't hot but warm
With the immersion heater on the shower gets hot.

But I think they did replace the pump and do some work on the S plan when the boiler was replaced - and I had a feeling this all happened when the boiler was replaced. I think they should come and fix it for her but they've already told here it was the shower and she had a new shower fitted on there advice.
 
I’ll refer to my post #4

It could be that with the higher water temperature, the Shower thermostat valve is opening.

When the valve isn't allowing a hot flow, your in and out of the pump is going to be cooler as there is little flowing though it.
 
I think ill leave it tonight. I've turned the thermostat at the front of the tank up to 65 it was at about 59.
I'll go back tomorrow and have a look - maybe one last go - and maybe I'll advise here to get them out to fix it.
But thanks again I really feel like this has helped and if they do come back I can mention the pump etc. I'm not looking forward to it I know there be all defensive etc.
 
Must admit, i am getting confused myself following this but do hope you get it sorted. At the moment i cannot fathom whether the pump runs both for hot water at the tap and shower.
1. Try run hot tap until water is hot, check temp at pump is it the same temp
2. Shut off hot tap and run shower until it is at its hottest, is the temp at the pump the same as the shower or same as when you ran the tap.

Reason i am confused is that there is talk of the shower take off from the cylinder being lower than the top take off and there is talk of the pump running when either tap or shower are running.
 
I know, is confusing now 9 pages

But the pump is only used when the shower is on - So this has ruled out other things such as pressure issues.

Also the Shower only gets proper hot with the immersion heater element switched on.
 
plugsandsparks said:
Reason i am confused is that there is talk of the shower take off from the cylinder being lower than the top take off and there is talk of the pump running when either tap or shower are running.
Click to expand...
There's a Suffolk flange fitted, so the shower hot water comes from about three inches lower down the cylinder than the rest of the hot water. This shouldn't make any difference to comparative water temperatures until the hot water is nearly all used up.
It would be very unusual to feed downstairs taps from the same pump that feeds the shower, but not impossible.
 
mainline said:
I wonder how the OP is getting on.
It's always nice to have an update on the outcome.
Click to expand...
I hate that when they just disappear ;)
Sorry, as you know I turned the thermostat up on the tank and yes it is warmer but it's not right and I do feel this has led me in the right direction because I did feel it wasn't right from when the boiler was changed.


I would like to get a thermometer suitable to measure the temp if anyone could recommend one?

Another thing if I quickly turn the temp right down and right up it is hot for like a second.

Also this has made me what to learn S and Y plan etc I've been putting it off - I'll probably start another thread at some point.

But I'll say it again this is a great forum with some really helpful people.
Mark.
 
I think the problem may be the shower mixing valve is designed for mains pressure and the OP has only tank gravity pressure, or the pump may be caput and will not operate correctly with the pressure now available with the new boiler, which again may be designed for mains pressure and only has gravity pressure, both need checking, whatever is causing the problem seems to be a disparity between the boiler, shower pump and tank pressure differentials.

The lack of gravity pressure equipment is a continuing problem for older house's and installations.
 
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Mike Johnson said:
I think the problem may be the shower mixing valve is designed for mains pressure and the OP has only tank gravity pressure, or the pump may be caput and will not operate correctly with the pressure now available with the new boiler, which again may be designed for mains pressure and only has gravity pressure, both need checking, whatever is causing the problem seems to be a disparity between the boiler, shower pump and tank pressure differentials.

The lack of gravity pressure equipment is a continuing problem for older house's and installations.
Click to expand...
The shower valve in question is designed for a minimum pressure of 0.4 bar.
It is fed from a purpose designed shower pump which should be capable of providing a pressure of 1.5 bar - 3.0 bar, depending on the exact model, so it should work properly.
The design and layout of all the plumbing we can see in the pics is OK, although a little odd in places.
There's something that has failed, is not set up properly, or is partially blocked.
I'm still unclear if the shower worked properly when the water was heated by electricity, or was just 'better'.
 
This is so simple..... get the temp of the hot water tested as close before the mixer as possible . If its as hot as expected .Buy a new mixer ..... !
 
Anyway like I said I feel I've been put on the right track - for some reason the water entering the pump isn't very hot, unless I use the Immersion. I think I'll measure the temp(i.need a thermometer) and just go to the company that fitted and say look this is the temp here's what I found, fix it.
 
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