Question on how a PRV works (single unit for two residences)
We have a 1" water line with 90-100 PSI from the city coming into the main house that goes into a PRV set to 60 PSI. It splits off into two 3/4" lines (feeding the main house, and a guest house).
If the main house has a shower + sink going, and the guest house has a shower + sink going.
Does the PRV compensate to ensure that we're always getting 60 PSI across 2 showers / 2 sinks? So the pressure stays the same.
OR
Does it set the PSI to 60 PSI, and that is shared statically across the two lines (i.e. say shower uses up 20 PSI and sink uses up 5 PSI). So shower turns on and pressure is now 40 PSI. Someone turns on the sink and then we're at 35 PSI. So when someone is tries to shower in the guest house their water pressure is trash.
Thanks!
Posted Feb 25, 2023, 4:25 AM UTC
When you use water you get whats called "residual pressure", that means the pressure while the system is in use. The PRV keeps the static pressure (as in the pressure that is constant with no fixture use and held in the system) at 60 PSI (OR whatever you want to set it at).
The PRV isn't there to compensate for residual pressure, that pressure is dictated by the source. The source doesn't supply at the constant pressure
Would you suggest going 1” to a T that splits to 3/4” and PRV at the ends (2 PRVs vs 1 PRV)?
Size changes volume of water not pressure, and I doubt to his would solve anything for you as it sounds like your pipes inside are under sized. If you truly have 90+ psi coming in before the PRV you wouldn't notice any drop in pressure even with 3 showers running, you would feel a drop in volume if the pipes were undersized though and the average person would call it the same thing because they don't recognize the difference between volume and pressure.