Shower Mixer not mixing water

[Ambaz79]

Hello

 

We have 3 Thermostatic showers that are fed by a 300L Presurerised Cylinder.  Water is heated by Ecodan ASHP but not sure this make any difference.  For some reason the showers will only give hot water or cold water.  If we are on hot and turn the Thermostat the water stays same temp to a certain point and then switches to total cold water if we turn it anymore.  

 

We have tried to swap the pipers for the hot and cold water into the shower but this has done nothing and the hot is still coming from the same side.  

 

Would you say this is a issue with all 3 shower Thermostats or a plumbing problem where the shower is not compatible with the water pressure? 

[markc]

First thought was that H and C were the wrong way but if you have tried swapping them over it has to be a pressure related problem … insufficient for that particular mixer design maybe

[markocosic]

What temperature are you storing the hot water at?

 

Cheapo mixers need a headroom of 5-10C for the hot water temperature and the mixed temperature. And a minimum about of cold water at part of the mix for stable operation.

 

If your heart pump is heading there tank to too low a temperature you can observe this behaviour.

 

Non thermostatic mixers (kitchen tap etc) won't do this.

[Temp]

6 hours ago, Ambaz79 said:

We have tried to swap the pipers for the hot and cold water into the shower but this has done nothing and the hot is still coming from the same side.

 

Can you elaborate on what you mean by "still coming from the same side"? If the same pipe into to the mixer is hot then either they wernt swapped over or something else is going on.  

 

Do the mixers need non-return valves on them? Check the instructions. I think most that need non-return valves are supplied with them fitted but best check.

 

[Big Jimbo]

I'm no plumber however, if the OP's water is coming from a presurised tank, then would both the hot and cold not be delivered to the shower mixer at the same flow/ pressure ? If both the supply pipes are the same size ?

[dpmiller]

8 hours ago, Big Jimbo said:

I'm no plumber however, if the OP's water is coming from a presurised tank, then would both the hot and cold not be delivered to the shower mixer at the same flow/ pressure ? If both the supply pipes are the same size ?

depends if the PRV/ safety group was fitted correctly.

[Conor]

We have 4 mixers in total in our house. Three work perfectly, the fourth won't do cold water, we have it all the way across on the cold setting for a comfortable shower.

 

Are all three of your showers the same make / brand? In that case I'd say the hot water isn't hot enough. Try setting your tank to 50c.

[Ambaz79]

15 hours ago, markocosic said:

What temperature are you storing the hot water at?

 

Cheapo mixers need a headroom of 5-10C for the hot water temperature and the mixed temperature. And a minimum about of cold water at part of the mix for stable operation.

 

If your heart pump is heading there tank to too low a temperature you can observe this behaviour.

 

Non thermostatic mixers (kitchen tap etc) won't do this.

On day one we were storing water at 50C however as this did not mix it was too hot to have a shower as a temporary fix I have dropped it to 42C.  The problem is there in both cases. The lowest the HP can heat the water from the settings is 40C so we are not far off that now. Yes the problem is only the shower mixers.  Taps around the house are not affected at all and work fine. 

[Ambaz79]

14 hours ago, Temp said:

 

Can you elaborate on what you mean by "still coming from the same side"? If the same pipe into to the mixer is hot then either they wernt swapped over or something else is going on.  

 

Do the mixers need non-return valves on them? Check the instructions. I think most that need non-return valves are supplied with them fitted but best check.

 

So when we turn the thermostatic controller clockwise its giving the hot water.  when I switched the pipes going into the shower it stayed that we need to turn clockwise to get the hot water.  Im not sure if they did require non return valves.  All the pipework is in the wall so would not be able to check.  The way I switched the pipes is from the loft as we have access there to the pipework where it T's down to the shower.  Can I fit a non return valve there? Also would it go on the hot or cold side? 

[Ambaz79]

14 hours ago, Big Jimbo said:

I'm no plumber however, if the OP's water is coming from a presurised tank, then would both the hot and cold not be delivered to the shower mixer at the same flow/ pressure ? If both the supply pipes are the same size ?

For hot water we have a 22mm pipe ring and we have T'd down to the shower with a 15mm Pipe.  The 22mm Pipe then returns back to the tank where we have a Circulating pump to keep the water warm in the pipe.  Even with the pump off it makes no difference. 

[Ambaz79]

5 hours ago, dpmiller said:

depends if the PRV/ safety group was fitted correctly.

Yes this was fitted by our installer for the air source heat pump.  He installed the HP and all the bits that go with it and then my builder ran the pipe work.  

[Ambaz79]

5 hours ago, Conor said:

We have 4 mixers in total in our house. Three work perfectly, the fourth won't do cold water, we have it all the way across on the cold setting for a comfortable shower.

 

Are all three of your showers the same make / brand? In that case I'd say the hot water isn't hot enough. Try setting your tank to 50c.

Yes Showers all the same Although they are not any major brand.   

[dpmiller]

do these mixers have one or two knobs?

[Temp]

15 hours ago, Ambaz79 said:

So when we turn the thermostatic controller clockwise its giving the hot water.  when I switched the pipes going into the shower it stayed that we need to turn clockwise to get the hot water.  Im not sure if they did require non return valves.  All the pipework is in the wall so would not be able to check.  The way I switched the pipes is from the loft as we have access there to the pipework where it T's down to the shower.  Can I fit a non return valve there? Also would it go on the hot or cold side? 

 

No they would need to be on each mixer.

 

Im not sure this is the problem but I've heard that when the valves are missing water can sometimes flow down a hot (or cold) pipe, through a mixer that is OFF and back up the other pipe the wrong way. From there it goes to another a mixer that is ON. So the one that is ON effectively has two hot feeds or two cold feeds. 

 

Perhaps try allowing all mixers to cool down fully then turn one on full hot. While that's running hot go to the other mixers and feel them to see if they are heating up. Don't turn them on just feel the mixer to see if its getting obviously hotter when it's been off for ages. 

[markocosic]

1 hour ago, Temp said:

 

Im not sure this is the problem but I've heard that when the valves are missing water can sometimes flow down a hot (or cold) pipe, through a mixer that is OFF and back up the other pipe the wrong way. From there it goes to another a mixer that is ON. So the one that is ON effectively has two hot feeds or two cold feeds. 

 

This can absolutely happen where pressures are imbalanced in any shape or form. Very common issue in apartment buildings with shared hot water systems.

 

Incorrect plumbing for the cold feed (taken from the non pressure balanced side) and no non return valves on the mixers would lead to this.

[markocosic]

Could also be crud in the valves. Here was our shower following some repairs to the apartment building...

 

 

The muck holding those check valves open caused backflow of cold water into the hot water system...much to the annoyance of our neighbours. 🙂

 

[Ambaz79]

Problem solved.  When I switched the pipes in the loft it turns out I switches the pipes for the Sink not the Shower Mixer.  What I did was from the wall switch the shower mixer upside down so the pipes then 100% changed and the mixer started working.  Now we just need to locate where the shower pipes come from maybe under the loft boards but not a major job to change.  Plumber coming in next few days to sort it out.  

 

Apologies for wasting everyones time!

[Mr Punter]

You can get shower valves for when the plumber has mis-piped the hot and cold.  I think Grohe do them.

 

https://www.showerspares.com/search/grohe_thermostatic_1_2_compact_cartridge_reversed_inlets_47175_000/

Edited September 13, 2023 by Mr Punter
link added

[Temp]

7 hours ago, Ambaz79 said:

Problem solved.  When I switched the pipes in the loft it turns out I switches the pipes for the Sink not the Shower Mixer.  What I did was from the wall switch the shower mixer upside down so the pipes then 100% changed and the mixer started working.  Now we just need to locate where the shower pipes come from maybe under the loft boards but not a major job to change.  Plumber coming in next few days to sort it out.  

 

Apologies for wasting everyones time!

 

With some mixers you can just take the cartridge out and put it back in a different position without redoing plumbing. This might be useful if only one mixer not all are wrong.

[Ambaz79]

Thanks for this!

 

Had an amazing hot shower that was thermostaically controlled.  All working fine now!