New unvented system - rubbish pressure

[bexxxxx]

Hi,

I am a newbie and know nothing - please keep it simple

Had a new unvented oso super s 300l (huge thing) fitted (unsed to have a gravity fed system - plumber suggested I can it changed when we had the aga removed and the immersion tank needed replacing, the loft tanks need removing also because they were unsafe).

He said it would be worth upgrading the entire system and that mains unvented would be an improvement and would remove the unsafe tanks in the loft.

Well it isn't an improvement - we have lost all our pressure and it cost a fortune to have much worse pressure than we had before - it almost dribbles out of some taps! Plumber has said that there isn't anything he can do about it and that he is only allowed to let 3bar into the property beacuse of regs or something?

The mains pressure must be good as we had really fast pressure before the supposed upgrade!

Is there anything that can be done about it - can it be improved?

Also should the shower slow down when water is run elsewhere - the plumber implied that one of the benefits of our new system was that the pressure wouldn't drop in the shower when water was used elsewhere?

Please help - I am fed up with waiting 20mins to run a bath!

 

[Youllneverguess]

From your limited information...

Poor street pressure
Inadequate pipe size
Idiot installer.

Not in any particular order.

Measure your mains water pressure and tell is what it is, along with the size of your supply pipe.

 

[leakydave]

Dirt / Debris in the filter gauze? as mentioned, before, cold pressure and flow rate would be useful to start with.

 

[bexxxxx]

The street pressure has been fantastic for years, it used to knock your head off when you opened a tap, you know the one - taps which drench you if you turn them on too fast.

The taps not changed only the system feeding it - so I suspect it's not rubbish mains pressure. Our cold used to come off the mains to the kitchen taps and was great - I thought that an unvented system used mains to feed the cold taps and so I wasn't expecting any change?

Does an unvented system use mains cold?

Sorry I am not good with plumbing - hence the limited information.

Managed to dig out the paperwork I have from the plumber which states the following:
I have had an expansion tank fitted.
The incoming static cold is 3.2bar (is that good or bad?)
The pressure reducing valve has been set to 2.5 bar
The operating pressure reducing valve is on the cylinder???
Hot water temp is 56C
OSO model SC300 - unvented
Says it is a sealed system with boiler flow temp of 72C
All the new pipe work is 22mm

Is any of the above any use? Or do I have to live with rubbish pressure - also should putting on a tap effect the shower?

 

[bexxxxx]

I have had alot of debris in the filters in the taps - do you think debris could be the cause?

Would that cause the drop in shower pressure when the tap is run?

 

[Youllneverguess]

Clogged filter on cylinders pressure regulating valve. And/or inadequate supply pipe.


Do not confuse pressure and flow.

 

[Youllneverguess]

Static pressure is not as important ad dynamic pressure. 3.5 bar is fantastic depending on where you are. In London yes, where I live, no.

 

[bexxxxx]

sorry you've all lost me?

Please explain - 'Static pressure is not as important ad dynamic pressure' and 'Do not confuse pressure and flow'.

I have 3.2bar static cold apparently (whatever that means?) and a 2.5 regulator - should the water be dribbling out the taps and should the shower pressure decrease when the taps are turned on?

I don't want to call the plumber out to fix it if there's nothing he can do about it?

 

[Youllneverguess]

You need to know the pressure in the system with water running. If it plummets the moment you turn on a tap then you have a blocka, restriction, inadequate supply pipe.

The installer should have sussed this out before starting.

 

[bexxxxx]

Ok - so how do I find out the pressure in the system with the water running?

 

[bexxxxx]

when you say inadequate supply pipe do you mean to the house or to the system, tap?? I don't know which supply pipe you are referring to?

 

[Youllneverguess]

You find out the pressure by using a pressure tester.

Your supply pipe is the water main, from the street to the cylinder.

But frankly, you are going to have to call a professional in.

 

[bexxxxx]

So I should probably ask the plumber to come back?
He'll just try and fob me off again..

What should I be asking him?

 

[Youllneverguess]

To see his g3 qualifications.
What the dynamic pressure is.
How big the supply pipe is.
Has the inlet filter on the regulator been checked and cleaned.

 

[Agile]

Better to call it dynamic flow rate.

Thats the flow rate whilst say 1.0 Bar pressure remains in the pipework.

Whilst 1.0 bar is a minimum pressure used for shower installation assessment a higher pressure is desirable with an unvented because the pressure reducing valve loses some pressure. Many would look at the 1.5 Bar dynamic flow rate hoping for at least 22 litres per minute.

Tony