What is this pressure valve I've got on my mains?

[indus]

Hello I have an adjustable valve on my mains pipe that says 'Caleffi series 355'.

It is set to 3bar but can be adjusted from there up or down.

What is the point of this, what is it meant to do?

Thanks

 

[transam]

Pressure reducing valve . In order to limit high water pressure to some thing !

Often found on un vented cylinders ( non adjustable ) to limit water pressure to 3 or 3.5 bars !!!!!!!!!

 

[indus]

Pressure reducing valve . In order to limit high water pressure to some thing !

Often found on un vented cylinders ( non adjustable ) to limit water pressure to 3 or 3.5 bars !!!!!!!!!

Thanks. I don't have an unvented cylinder though, I have a thermal store.

To confuse the issue more, today I measured the pressure from my outside tap which comes off the mains before this valve. It measures 3 bar, so if the pressure is already 3 bar why then install a valve that limits it to 3 bar??

( The whole system was installed by my plumber about 6 years ago. He has now emigrated so uncontactable!)

 

[Onetap]

To confuse the issue more, today I measured the pressure from my outside tap which comes off the mains before this valve. It measures 3 bar, so if the pressure is already 3 bar why then install a valve that limits it to 3 bar??

( The whole system was installed by my plumber about 6 years ago. He has now emigrated so uncontactable!)

Probably fitted to make the system more user friendly, e.g., wash your hands without getting a shower.

The mains pressure usually goes up at night.

 

[SimonH2]

...I have a thermal store.

It may well be that the manufacturer specified installation of a PRV if your mains pressure is likely to exceed 3 bar. Plate heat exchangers also have pressure limits, hence a PRV is common upstream of a combi boiler (or a heat bank).

When I bought the flat, the PRV had failed (the valve seat had eroded, and so it didn't properly shut off). With no water being drawn, the pressure would regularly be off the scale which stopped at 6 bar. The PHE in the combi survived it though.

And as Onetap wrote, it can make the system more user friendly be reducing the tendency for the taps to do an impression of a crowd control water cannon