New Shower mixer airlock help

[Wictod]

Hi,

Recently had a horizontal bar mixer fitted at my daughters house shower as part of a bathroom refit. Having trouble getting the plumbers back round and we have an issue with getting any water out of the shower. I have had the mixer off the wall and replaced and it then works ok for about a week but it's stopped again.

The hot water is fed to the shower by a pump (1.5bar grundfos under the bath) from gravity fed tank and the cold water appears to be mains pressure.

All we are getting is a few drips out of the shower head on both full cold and full hot settings on the control handle.

Does this sound like an airlock or faulty cassette.

Thanks

 

[footprints]

Does the water drop down to the mixer if so the elbow above is the most common place for an air lock, is there any means of venting?
Is the pump kicking in?
Unusual to have pumped hot and cold main.

 

[Wictod]

From what I remember the connection to the mixer is straight from the wall but will check.. not sure about the venting sorry?
The pump kicks in but will not kick in by just using the mixer water control.. we have to run the hot water tap in the bath with the shower set to on then back off hot water tap and then the shower suddenly comes to life.. This was how it operated on the old setup which worked ok. Not ideal way for it to work I know.
I"m assuming it's mains fed cold due to the pressure of the cold water, it's considerably more powerful that the hot even when the hot pump is working.

Currently can't get any water out of the shower regardless of whether it's full hot or full cold setting on the mixer control.
Thanks

 

[footprints]

Did you have to turn off the mains when you removed the shower or just the tank supply?
It also sounds as though you might not have enough head of water to trigger the shower pump flow switch.
How many connections on the shower pump two or four?
I know it is a pain but it really is something the plumber should fix for you, it sounds like there is a fundamental problem with the installation rather than just a faulty component.

 

[Wictod]

Thanks footprints.. I isolated both the hot and cold from underneath the bath with those lock off valves on both feeds.

The shower pump has just two connections in and out for the hot..

Update; I've just been round there after reading your first post and with the water on undone one the big nuts (the hot side) that connect the shower to the wall... obviously a lot of water started running out then the pump kicked in and quickly tightened the nut back up and the water started flowing through the shower head. I'm assuming this might be the airlock you mentioned in the elbow joints.. If it is, how do you overcome this issue?

Thanks

 

[footprints]

At a guess it sounds to me like there is not enough head to overcome the resistance put up by the shower.
Head is the pressure exerted by gravity due to the distance between the water level in the tank and the shower head there needs to be enough to move the switch in the pump to start it.
Out of interest try laying the shower head in the bath when turning on it might just be enough to get the pump started.

 

[Wictod]

I've tried that with the shower laying in the bath but doesn't have any effect. I think you"re right about the head pressure. I've got a feeling the unit they fitted is a 2bar pressure requirement. I've seen units that operate between 0.1 - 5 bar, reckon I need a lower pressure one.. thanks

 

[terryplumb]

You need to verify if cold is from mains. If it is ,the mains pressure may be keeping the non return valve on the hot side closed ,preventing hot water flowing into the mixer valve. Never a good idea to supply a thermostatic mixer valve with hot and cold at different pressures.
If you turn off the cold supply isolator and set the temp to hot ,does the pump run when turning the valve on ?

 

[Wictod]

terryplumb, I'm almost certain it is mains fed cold but will verify when I go round the daughters house again tomorrow.. I'll isolate the cold feed, set to hot and see if it flows once the pump engages.. makes sense this test.. Thanks

Is there any mileage in trying to balance the cold feed with the hot by closing off the cold feed isolator slightly?

 

[terryplumb]

That will not alter pressure at all. It would restrict flow only. Have you checked the filters on the Inlet ports of the valve ?

 

[Wictod]

Ahh ok, thanks for clarifying that..

I've had them out of both sides a week ago (if you mean the hot and cold inlet feeds to the mixer bar), the hot was clear but the cold had some minor contamination most likely from a rough cut of the plastic speedpipe they fitted on the cold side.. only a few tiny bits of crap though no blockage.

Thanks

 

[terryplumb]

Just re read your earlier posts ,and I doubt the cold is from the mains. As you stated that when the mixer valve is set to coldest setting ,no water comes from the shower head. If it was fed from the mains ,cold water would flow strongly. You would not get an airlock on the mains cold.

 

[Wictod]

I may have misled you there although I can't be certain until I verify whether it is mains fed... There were occasions when trying to get this working where the cold wouldn't work as well as the hot.,, however, this morning when I popped round there the cold was working but not the hot... I almost certain it is mains fed cold but will double check..

Thanks

 

[terryplumb]

Does the pump supply hot exclusively to the shower ,or also the bath /basin/sink ?

 

[Wictod]

The pump is a grundfos SSR 1.5 and only supplies hot to the bath tap (which is a standard tap physically separate from the cold tap) and the shower mixer. From under the bath you have the gravity fed hot feed coming into the pump then the pump output is connected to a T piece with one leg going to the bath tap and the side off to the shower mixer. To get the hot to run out of the shower (when it works ) is to turn the shower on.... some drips then start coming out the shower head... then turn the bath hot tap on to activate the pump, then back off the hot bath tap to a dribble with the pump still running then the hot water suddenly comes out of the shower head and you can control the require heat from the temperature control.. I know it's a crap setup, I'm not a plumber obviously but I think the installers just done a like for like replacement without considering how this should work effectively. Thanks