Water pressure help!

[Faffandahalf]

We’ve been renovating a house and been through 2 sets of builders.
First set did most of the plumbing.

We have a mega flow tank and a valiant boiler in the utility next to main bathroom ok first floor

The water pressure is all over the place.

Kitchen fine
Downstairs loo fine
Loft sink fine
Main bathroom shower not amazing but passable.

However main bathroom sink and loft shower is ridiculous. Very very slow flow. Shower would be impossible to use. Sink is usable but definitely not normal.

Second set of plumbers have refused to do anything saying it wasn’t them that did the work and they have no idea what’s wrong.

Any ideas? We really really cannot rip up anything and start again!

"We really really cannot rip up anything and start again!"

You can, you know, if you want it fixed.

Probably it is a combination of small-bore pipes and constricting valves. If they are under the floor you will have to take them up and have a look. If you think that flooring is in some way permanent and can never be lifted to get at the pipes and wiring, you will soon know better.

however

You need to know the facts. Get a bucket. Fill it at each hot tap, each cold tap, and each shower in the house. Accurately measure how long it takes. Calculate litres per minute. You will then be able to describe the problem.

It is especially important to know the lpm from the kitchen sink cold tap, and the garden or utility room tap if you have them, since this is likely to be the best flow your house can have.

How old is the house?

Do you think the incoming watermain (between the meter or stopcock under the pavement, and the one in the house, is copper, lead, iron or plastic?

Is it the size of your finger or the size of a banana?

Are any of your taps flashy stylish little Italian mixers with tails the size of pencils, and a ceramic cartridge operated by a joystick?

Are you in a town?