New Bathroom, new taps, poor flow!

[thewelshman]

Hi, I have fitted a new bathroom, and have just fitted the new bath/shower mixer and the flow is terrible. The taps I have are rated for 0.5 bar pressure.

I am running off a traditional gravity system.

The shower has a pump which (when connected) should provide ample pressure but the bath is bugging me.

Now I can easily up the cold water pressure by running mains pressure to the bath (there is a mains cold nearby, but if I connected this whilst leaving the hot feed on gravity, what would happen? Would I still get hot water through the tap?

Any help/suggestions appreciated.

I have thought of moving the shower mixer to power the whole bathroom but this would be very complicated.

 

[thewelshman]

Just read this post:

I have seen check (non return) valves in monoblock taps - little plastic things which you should ditch immediately. They sit in the tap just inside where the flexies/pipes screw in. They're a cone against a seat, held by a spring, which almost stop all flow!

Seen flow restrictors in a shower mixer too. Better out than in, unless you have multiple showers etc..

My tap is not monoblock, but is a shower/mixer, are these non-return valves likely to be in it? If so, should I remove them?

 

[thewelshman]

These are the taps

http://cgi.ebay.co.uk/ws/eBayISAPI....40028334786&rd=1&sspagename=STRK:MEWN:IT&rd=1

 

[TicklyT]

Is the tap suitable for the pressure you have available on your hot water supply?

Quick back of an envelope type calculation like:-

1 bar = about 10 Metre head (vertical distance between storage tank and tap outlet)
0.5 bar = 5 Metre head required by tap.

A typical setup with bathroom on 1st floor and storage tank in loft above would give about 2.5 Metre head or about 0.25 bar of pressure....

Unbalanced pressures for the feeds to the mixer may result in cold water back feeding to the hot supply unless a check valve is fitted in the hot supply, which could further reduce the hot feed rate. It may also be impossible to regulate the temperature at the mixer.

If it's any consolation I've fitted a kitchen tap requiring 0.5 bar minimum pressure, which I have just about got on the ground floor with a gravity feed, but the flow rate is still disappointing. I'm considering either changing the tap or pumping the hot water for the whole house.

If your booster pump is single ended you may get away with using it to boost the hot pressure, but double ended shower pumps are set up differently to whole house pumps. there's always a flow on both hot and cold sides of a shower pump, but whole house pumps are set up with a bypass. This means if only one tap is opened the other side isn't pumping against zero flow, causing cavitation and damaging the impeller.

 

[thewelshman]

That's the problem in a nutshell, taps are rated 0.5 bar, but I only have 0.3 bar pressure.

Looks like I may have to live with it until we change to a combi.

 

[djbobbins]

We had identical problem when we had our bathroom fitted and the man (can't bear to call him a plumber) fitted quarter turn ceramic disk taps to a gravity fed system with about 4 feet of head.

1930s taps = fine

2000s taps = useless flow on hot alone, excellent flow on cold (mains pressure). When both on, cold back-flushed up the HW pipe.

Solution we came up with was maybe a bit excessive - sold the house three months ago...

 

[JohnD]

That's the problem in a nutshell, taps are rated 0.5 bar, but I only have 0.3 bar pressure.

Looks like I may have to live with it until we change to a combi.

it would be cheaper to buy different taps.

edited - curses, i didn't notice the q was posted last October. i don't suppose he's interested now.