Low water pressure in bath mixer tap for shower head?

[christoperrobinspipe]

Hello - am hoping someone out there can offer some advice...

I've been living in a split level 1st & 2nd floor masionette for two months, which was built in the 60's.

Heating is provided via combi boiler. Water for kichen is fed straight from the mains supply (both hot and cold), however, we have separate bathroom and WC upstairs with setup as follows:

Hot water (bath and sink) is fed via mains/combi - water pressure is excellent.
Cold water (bath, sink and toilet) is fed by a cold water tank in an elevated water tank cupboard/loft space in the bathroom - water pressure is poor.

Our toilet takes over 8minutes to fill. The water pressue in the bathroom sink is poor.

The strange thing about the bath (which is a mixer tap with shower head hose connected) is that the pressure via the cold and hot water taps (when running just a bath) is almost identical, and I can balance the hot vs cold nicely for desired temperature. However, when you run the shower the water pressure is great if solely running the hot tap (as you would expect as its fed off of the mains water supply), but as soon as I dial in some cold, the water pressure is so poor I simply don't use cold water anymore whilst running a shower. So I am basically reliant upon the hot water temperature set on my combi boiler to act as the max temperature for my shower hose.

I don't know enough about bath mixer taps, but it just seems odd that the water pressure for both hot and cold on the main bath taps is fine. But as soon as you activate the shower... the cold water is pretty much unsuable.

I know the immediate solution would be to simply connect all my cold water supply to the mains. But this still doesn't explain why the water pressure for my shower is so poor the moment the cold water tap is turned on. I understand gravity, elevation etc, but then wouldn't the bath cold tap have poor water pressure too, as that is still getting the water from the tank above?

Does anyone have any ideas? Any help would be greatly appreciated

 

[Ben-gee]

You are confusing pressure and flow.

Your system is behaving exactly as one would expect.

And yes the solution is to make all the cold water mains pressure- luckily this is a trivial thing to do.

 

[christoperrobinspipe]

You are confusing pressure and flow.

Your system is behaving exactly as one would expect.

And yes the solution is to make all the cold water mains pressure- luckily this is a trivial thing to do.

Re "your system is behaving exactly as one would expect" - I can't imagine this pipework has been set up by design, and the various occupiers living here since 1961 have not used cold water when using the shower due to the significant reduction in pressure/flow? You literally cannot have a shower if you turn the cold water tap on. It's like somone standing over you with a watering can. But with less water!

 

[Ben-gee]

Yes but as it is now, with mains pressure hot from a combi and gravity cold from the tank.
In 1961 the hot would also have been gravity fed and all would have been fine with equal pressures. Someone has “improved” it along the way - but unfortunately didn’t finish the job if what you say is correct.

 

[christoperrobinspipe]

Yes but as it is now, with mains pressure hot from a combi and gravity cold from the tank.
In 1961 the hot would also have been gravity fed and all would have been fine with equal pressures. Someone has “improved” it along the way - but unfortunately didn’t finish the job if what you say is correct.

I think that is most probably the case. I was hoping someone might say "there is an issues on the mixer tap and you need to do x/y/z". I'll be getting someone out to take a look/quote in the next few weeks hopefully.

 

[Ben-gee]

It’s just a case of empty the cold water storage tank, cut the gravity cold water feed where it comes out of the tank, cut the cold mains feed that used to fill the tank - and join the two together - then all the cold will be on mains pressure.

 

[adomas]

You are confusing pressure and flow. Your system is behaving exactly as one would expect. And yes the solution is to make all the cold water mains pressure- luckily this is a trivial thing to do.