shower temperature control issue

mickdw

Just had a new shower fitted. It has a grundfos pump in hot press pressuring the hot and cold feeds to the shower unit.
The shower is typical enough with a turn dial for on and off and another for temp.
The issue is that the temp will be at full hot then if turning it down in small increments, it won't change at all until it will then suddenly go full cold at some random position.
So say there are 10 temperature positions. It will be full hot from 10 down to maybe 4. I would then expect that it would go full hot again at 5 but no, to get heat again I would have to move it to 8 at which point it goes full hot instantly.
Any ideas?

Sleeper12

What does the installer have to say about it?

Try running it with the pump turned off. This will give you some indication if the pump is causing the issue.

It could be a blocked filter in the pump or in the shower. It could be a faulty cartridge.

I'd definitely get the installer back to give his opinion

mickdw

He is just going to say faulty pump or faulty shower. That is why I was trying to get an opinion here hoping Someone might have seen it before.
The install looks okay according the pump installation instruction however the instructions do suggest that pipework should where possible run up and over to get to shower whereas in our case, it loops down under the floor from the pump to the shower. Pump is located beside cylinder in hot press.

Dardania

Is it possible the installer put the hot pipe to the cold inlet and vice versa?

You can check that by looking at the shower manual, which should indicate which is which, and then running the shower and seeing which pipe is hot.

Sleeper12

mickdw wrote:

He is just going to say faulty pump or faulty shower. That is why I was trying to get an opinion here hoping Someone might have seen it before. The install looks okay according the pump installation instruction however the instructions do suggest that pipework should where possible run up and over to get to shower whereas in our case, it loops down under the floor from the pump to the shower. Pump is located beside cylinder in hot press.

Pump has no warranty if its not piped to manifacture spec's. They aren't a suggestion, they are instructions.


A friend replaced a Salamander pump last year. Like for like so he didn't do the original pipe work. Pump failed & Mt Agencies sent out an engineer to repair under the warranty. Engineer took one look and said that he couldn't look at it till it was piped correctly. Pipes had to go straight up as far as I know. Engineer was very good and didn't charge a call out but it shows the importance of following instructions provided by the manufacturer

K.Flyer

Stuart Turner are the same, the flexi connection pipes must be straight up, but after that the pipework can go whichever way is required.
As said above, I would check that it is piped correctly and that hot water is going to the hot side of the valve.
Does the pump service bathroom taps as well and is the pressure even on both sides?
Most likely the shower valve is a thermostatic valve, check temperature of the water at a basin tap and compare the reading to the manufacturers data, if the temperature is excessive, the cartridge may be closing and restricting the flow of hot water.

mickdw

Sleeper12 wrote: »

mickdw wrote:

He is just going to say faulty pump or faulty shower. That is why I was trying to get an opinion here hoping Someone might have seen it before. The install looks okay according the pump installation instruction however the instructions do suggest that pipework should where possible run up and over to get to shower whereas in our case, it loops down under the floor from the pump to the shower. Pump is located beside cylinder in hot press.

Pump has no warranty if its not piped to manifacture spec's. They aren't a suggestion, they are instructions.


A friend replaced a Salamander pump last year. Like for like so he didn't do the original pipe work. Pump failed & Mt Agencies sent out an engineer to repair under the warranty. Engineer took one look and said that he couldn't look at it till it was piped correctly. Pipes had to go straight up as far as I know. Engineer was very good and didn't charge a call out but it shows the importance of following instructions provided by the manufacturer

They actually are a suggestion from the wording in the installation manual.
It says, where possible, pipework should run up and over.
I should have mentioned that there are vertical flexible sections installed at the pump then it runs horizontal into side attic and down under first floor.
Hot and cold being mixed up at the show sounds like a good shout though too.