Mains pressure issues

[Lambed84]

Hi all.
I've inherited a job that's the customer has spent a small fortune on and needs rectifying.
So the layout is as follows.
System boiler.
Unvented cylinder.
Mains static 1.5bar
Dynamic 0.5bar
Flow rate 8LPM
5 mixer showers, 4 of them ensuite.
1 bath.
Secondary return.
Issue is they can't have more than 1 outlet open at a time due to the poor flow rate/pressure.
have checked combi valve and incoming main at point of exterior and interior stop tap.
The water main is new from outside stop tap.
So, I'm left with either 1) the new main has a blockage. 2) pump the mains supply.
Previous engineer has attempted to solve via fitting a GWS 1000L vessel, which seems to do nothing. It appears he's missed the pump bit.
In finality, my question is what would you do to solve the above. Advise they start from scratch or fit a booster pump to the vessel that's already in situ?

TIA

 

[ShaunCorbs]

Need a break tank and pump as you need to boost the pressure have a look at the dab easy sys

 

[EvilDrPorkChop]

Have you had Water board out to check the supply and make sure there's no issues in the street?

My parents had an issue once, and turned out they hadn't turned the main stopcock on at the top of the street!

 

[Lambed84]

Have you had Water board out to check the supply and make sure there's no issues in the street?

My parents had an issue once, and turned out they hadn't turned the main stopcock on at the top of the street!

As stated, has been checked. Its the new style plastic tap.
Thanx.

 

[Lambed84]

Need a break tank and pump as you need to boost the pressure have a look at the dab easy sys

Thanx.
Having had a quick look on their website they di a lot of gear!
The NBB range us what I'd be looking at?

 

[ShaunCorbs]

ESYTANK | DAB Pumps

480 liter tank provided with e.sydock for quick installation. It is suitable for potable water and is equipped with filling valve from the water supply (complies with UNI EN 1717), with AG type overflow system, suction hose with bottom valve and discharge hose. The tank is suitable for...

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