Low pressure on Mira Combiflow shower

[richardc1983]

I'm getting 10l/m on our Mira Combiflow shower done via the bucket test both with and without the shower head attached. We get 12l/m on all other taps hot and cold through the house.

Mira came out and replaced the cartridge under warranty and cleaned the filters out. Any flow reducers or savers have been removed so I am not sure why the flow is still down, this makes the shower just that little bit less pleasant. All cut off valves etc are fully open. The only thing left is the filters but they are clean and the shower cannot be fitted without them. I www thinking of drilling a hole through the filter to allow water to pass through?

Any ideas? This is the manual http://www.mirashowers.co.uk/onlinecatalog/pdf/p4479_2.pdf

Regards

 

[longdogs]

Are the isolation valves full bore?

 

[richardc1983]

Are the isolation valves full bore?

How do you mean full bore?

 

[longdogs]

Are the isolation valves full bore?

How do you mean full bore?

http://www.screwfix.com/p/15mm-isolating-valve-pack-of-10/32802

http://www.screwfix.com/p/15mm-full-bore-isolating-valve/46860

Notice that they are slightly different shapes and full bore are slightly bigger. A non full bore can reduce the flow (not pressure)

 

[richardc1983]

Think they are full bore.

 

[Madrab]

If you drill the filters then there's no point in them being there. They're there for a reason.

Running through the restricted spaces of the pressure balancing valve and water channels and the action of the mechanism itself, I would always consider a small reduction in flow compared to a tap normal TBH.
Unless you have seen a drop in performance from when it was first put in then I would consider that being what the shower may flow.
The pressure of the water is a different subject if that's what you talking about

 

[richardc1983]

If you drill the filters then there's no point in them being there. They're there for a reason.

Running through the restricted spaces of the pressure balancing valve and water channels and the action of the mechanism itself, I would always consider a small reduction in flow compared to a tap normal TBH.
Unless you have seen a drop in performance from when it was first put in then I would consider that being what the shower may flow.
The pressure of the water is a different subject if that's what you talking about

Mira said it should be capable of a much higher flow. I tried again today and I'm getting just over 10l a minute flow wise.

 

[Madrab]

What is the rated max flow rate, did they give you a figure?

Remember that no matter how high the flow, if the pressure isn't reasonable then it won't 'feel' any better? You can have a great shower at 8 l/min because the pressure's excellent so it 'feels' great.

How is the shower fed? Un-Vented HW? Pumped?

 

[richardc1983]

What is the rated max flow rate, did they give you a figure?

Remember that no matter how high the flow, if the pressure isn't reasonable then it won't 'feel' any better? You can have a great shower at 8 l/min because the pressure's excellent so it 'feels' great.

How is the shower fed? Un-Vented HW? Pumped?

It's direct from the combi boiler, not sure of the flow put remember him saying 20l/m

 

[Madrab]

What boiler model do you have?

 

[richardc1983]

What boiler model do you have?

Glo worm 30cxi

 

[Madrab]

OK .... soooooooo ..... process of elimination -

Boiler flow's 12.3L/min @ 30deg rise
Taps flow 12L/min @ 30deg rise

Only thing that's left is supply pipes or shower that's restricting flow.
Only way to really test is to take the shower off the supply pipes, do the pipes flow 12L/min? if so, the shower's where the restriction is, either within the body or the pipe.

Unfortunately it the only way to be sure really if an extra few L/min is what you're looking for.

 

[richardc1983]

OK .... soooooooo ..... process of elimination -

Boiler flow's 12.3L/min @ 30deg rise
Taps flow 12L/min @ 30deg rise

Only thing that's left is supply pipes or shower that's restricting flow.
Only way to really test is to take the shower off the supply pipes, do the pipes flow 12L/min? if so, the shower's where the restriction is, either within the body or the pipe.

Unfortunately it the only way to be sure really if an extra few L/min is what you're looking for.

The bath taps are fed off the same pipes as the shower directly above and I get 12l/m there from both hot and cold. The new cartridge in the shower is the same as the other one they replaced. Only thing I can think is the flow cartridge that wasn't replaced but I guess that only controls if the shower is on or off. My shower isn't a true mixer shower. I found this info:

"The shower control mixes hot and cold water to the desired temperature and automatically compensates for variation in supply pressures. A ceramic based mixing cartridge is backed with a separate pressure-balancing cartridge. However, it will not compensate for changes in either of the temperature of the hot and cold water supplies. With its ultra-stylish contemporary looks and powerful water flow, its high-pressure mixer valve uses the latest technology, and you can adjust both temperature and flow with just one easy-to-use control."

 

[Madrab]

Yep, you don't have a thermostatic mixer there, is a pressure balanced manual shower, so maintains a balanced pressure from both supplies through the Pressure Balancing Cartridge (PBC).

You control the temperature manually and it's reliant on the flow temp staying the same to avoid a rise/fall in outlet temp

There are 2 cartridges, the flow cartridge and the PBC, they replaced the latter did they? The former is the one that controls the flow?? I would be looking there and would have expected Mira to have started there too given that controls the amount of water flowing through the shower??

 

[richardc1983]

Yep, you don't have a thermostatic mixer there, is a pressure balanced manual shower, so maintains a balanced pressure from both supplies through the Pressure Balancing Cartridge (PBC).

You control the temperature manually and it's reliant on the flow temp staying the same to avoid a rise/fall in outlet temp

There are 2 cartridges, the flow cartridge and the PBC, they replaced the latter did they? The former is the one that controls the flow?? I would be looking there and would have expected Mira to have started there too given that controls the amount of water flowing through the shower??

Yes I might ring them again tmrw and speak with them as something isn't right is it.