Reduced cold water flow to bath

Hi all. I've recently had a bathroom refitted by contractors. The original bathroom, probably fitted in 1980s, had a "telephone" type bath/shower mixer which (as my bath cold water is mains supply), worked very well with plenty of force in the water.

Since resiting the bath at right angles to its original position, and installing a new "Tre Mercati" bath/shower mixer, the force has reduced considerably. The plumber replaced the isolation valve with a lever type which apparently allows a larger aperture, but it's still rubbish. He assures me that there is nothing further he can do, and it must be resistance in the taps.

On poking around, I notice that though the hot water supply to bath is in 22mm, the cold is in 15mm. Before I make a tit of myself by raising this, could anyone let me know if this is normal practice with a cold mains feed to a bath?

The contractors had the old pipework and taps away before I could blink, so I can't confirm whether it was originally in 22mm. Also - the whole thing has now been beautifully tiled over, so I can't look under the boards.

Any help would be really appreciated - I'm desperate to get back my basic but very efficient shower.

what is the hot flow like ?
is the hot mains or gravity ?

Hi

The hot is gravity from a cylinder on the same level about 30 feet away. It seems to be more or less the same as it was before the work. Thanx

Oops - sorry - make that about 15 feet away, for the hot water cylinder to the bath taps.

it should still be good even though its on 15mm as it is from the mains.
is it slower than than hot ?

It's difficult to judge by hand, but I would say the cold is just fractionally faster than the hot - there's really not much in it.

if the taps are 3/4" i can't see that he reduced it to 15mm, i would of said it was like it before he changed the taps.

If that's the case - any ideas on what else might be causing such a significant drop in flow? The bath/shower mixer taps were medium/expensive and the tech support at the manufacturers said there should be no problem. The bath itself hasn't been moved very far - just pivoted 90 degrees. All valves are fully open - so I'm a bit stuck!

Was the shower mixer designed to work on low pressures?

It is not unusual for brassware to be designed for a minimum water pressure greater than 1 Bar. Gravity system pressures may be as low as 0.1 Bar.

Hi, the fitting is one of those telephone type standard bath shower mixers, and both the plumber merchant I bought it from and the technical bods at the manufacturers have confirmed it's a basic tap - not high pressure or anything. Also - the cold fill is on the mains anyway. My suspicious are still lurking with the 15mm pipework - especially as cold fill has 90 degree elbow at floor level.