Poor water pressure in pressurised system!

[Ula NI]

Help figuring out why the water pressure is poor?
Pressurised heating system in the house, built 20 years ago out in the country.
Upstairs water pressure is poor in bathroom, it was never great, but livable (would always have known if someone turned on a tap downstairs when you were in the shower!)...last few months it has been alot worse, when in shower, or turn on bathroom taps, the pressure will go from poor to weak back to poor. Bath has standing tap, it would take an hour to fill. All taps upstairs are mixer.

Plumber not sure of reason, but was going to start with replacing pressure reducing valve under kitchen sink where water comes in? He replaced gauge under sink already which sits just under 2 and drops to 1 whenever a tap/ other is turned on? But this is very tight space with little room for manoeuvring pipes which he says will be expensive (photo)?
Can you think of anything else that could be wrong?

On a side note, we had a leak in the bath tap too, but pressure had been bad before that. Plumber has replaced with new fixture from underneath (photo) as ceiling is open at the min, waiting on plasterer, but pressure is pathetic for bath. Also, boiler room aqua system white small expansion vessel was replaced.
Sorry for essay, and appreciate any advice.

 

[Johntheo5]

Assuming the mains supply is from the stop cock (blue piping) tothe left of the PRV, then that supplies 3 other items??, what are these 3 items? what does the PRV supply?, did the plumber take static and dynamic pressures from before the PRV? say at a (the) outside tap?.

 

[Madrab]

Just to get an understanding of your system, can you confirm ..... a guesstimate that the unfettered supplies from the mains in PIC 1 are -

Downwards - appliance supply, then an outside tap then into PRV for the rest of the house
Upwards - Up to the sink tap

Pic 2 - is that the shower outlet?

Pic 3 - boiler and Unvented (UV) with another 2 PRV's - higher PRV covering the CH so the system pressure is maintained - IMO that's a terrible cop out that could be a coverall for a system that may be losing pressure over time
2nd PRV covering the unvented.

If you are getting an initial drop in pressure and it then returns then it could be one of 3 things - The mains PRV getting tired or conversely, the UV's PRV getting tired - have they checked the pre-charge on the UV too?

 

[Ula NI]

Just to get an understanding of your system, can you confirm ..... a guesstimate that the unfettered supplies from the mains in PIC 1 are -

Downwards - appliance supply, then an outside tap then into PRV for the rest of the house
Upwards - Up to the sink tap

Pic 2 - is that the shower outlet?

Pic 3 - boiler and Unvented (UV) with another 2 PRV's - higher PRV covering the CH so the system pressure is maintained - IMO that's a terrible cop out that could be a coverall for a system that may be losing pressure over time
2nd PRV covering the unvented.

If you are getting an initial drop in pressure and it then returns then it could be one of 3 things - The mains PRV getting tired or conversely, the UV's PRV getting tired - have they checked the pre-charge on the UV too?

Yes to pic 1 description, pic 2 is the new 'easy plumb' bath tap fitting put in from underneath as the below room ceiling is currently open.
Kitchen tap has no issues, 2xoutside taps have no issues.
Pic 3, boiler room, forgive me for not knowing everything you're asking-
Both the small white expansion vessel (3 weeks ago) and red expansion vessel are not failing (sound hollow).
Can I ask what you think the cop out is?

 

[Ula NI]

Assuming the mains supply is from the stop cock (blue piping) tothe left of the PRV, then that supplies 3 other items??, what are these 3 items? what does the PRV supply?, did the plumber take static and dynamic pressures from before the PRV? say at a (the) outside tap?.

Yes blue is mains, 3 others are outside tap, dishwasher, kitchen sink.PRV then goes to boiler room (&possibly utility?) Dynamic and static pressures, not sure.

 

[Johntheo5]

The HW cylinder (seems) has its own PRV fed via the pipe with yellow handled lever valve, is this supply from the mains or from the other PRV and is the HW flow also poor?

 

[Ula NI]

The HW cylinder (seems) has its own PRV fed via the pipe with yellow handled lever valve, is this supply from the mains or from the other PRV and is the HW flow also poor?

Not 100% , but most likely coming via prv under kitchen sink. Hot water is as poor upstairs as the cold. All mixer taps/fittings. Is 2bar sufficient pressure coming into house @prv under sink? It drops to 1bar when water is called for anywhere other than kitchen.

 

[Johntheo5]

Not 100% , but most likely coming via prv under kitchen sink. Hot water is as poor upstairs as the cold. All mixer taps/fittings. Is 2bar sufficient pressure coming into house @prv under sink? It drops to 1bar when water is called for anywhere other than kitchen.

2.0bar after the (main) PRV is a bit on the low side (3.0bar is obviously better and the standard) but fairly acceptable if (2.0bar) maintained dynamically at say a flowrate of ~ 20LPM but yours is falling to ~ 1.0bar at probably a much lower flow rate, this could obviously be a faulty PRV or dirt in its strainer and that's why the pressures (both static and dynamic) should be taken upstream of this PRV, if the upstream (mains) pressure is say still 4.0bar with the PRV showing 1.0bar at say 15LPM then obviously a PRV problem but if the mains pressure at this ~ 15LPM is also only 1.0bar then a problem somewhere in the mains or simply the supply pressure is too low, thats why you should take both static and dynamic mains pressure at 15/20LPM.
The HW cylinder PRV should, ideally, also be fed from the mains.

 

[Ula NI]

2.0bar after the (main) PRV is a bit on the low side (3.0bar is obviously better and the standard) but fairly acceptable if (2.0bar) maintained dynamically at say a flowrate of ~ 20LPM but yours is falling to ~ 1.0bar at probably a much lower flow rate, this could obviously be a faulty PRV or dirt in its strainer and that's why the pressures (both static and dynamic) should be taken upstream of this PRV, if the upstream (mains) pressure is say still 4.0bar with the PRV showing 1.0bar at say 15LPM then obviously a PRV problem but if the mains pressure at this ~ 15LPM is also only 1.0bar then a problem somewhere in the mains or simply the supply pressure is too low, thats why you should take both static and dynamic mains pressure at 15/20LPM.
The HW cylinder PRV should, ideally, also be fed from the mains.

Thank you for all the advice, I'll ask the plumber to take the static and dynamic pressure and go from there.

 

[Madrab]

Can I ask what you think the cop out is?

The PRV that looks like it's maintaining the CH system pressure.

All CH systems should have a removeable braided filling loop that is protected by a double check ISO valve and another ISO valve, one at each end. This valve is manual and the braided pipe removeable for a reason.

Your system seems to have a PRV, that will probably be set to 1.5bar, and what may be a check valve after it - if it's an ISO then that's different but cant see from the pic though. If it's not an ISO then any time the CH system pressure drops, this PRV will top up that system pressure. This is not a good setup IMO. If the CH system has small leaks anywhere this system will automatically keep adding water to it to maintain that 1.5bar. Most times I have seen this done, it's when there is a persistent pressure drop that couldn't be for

2 fundamental issues with that IMO.
1- If there is a burst in the CH system at any time, that valve will just keep feeding the pipework until it's stopped potentially causing a mega amount of damage
2- if there is a small leak at any time this valve will keep on topping up the system with fresh oxygenated water, accelerating system corrosion.