Reccommended water pressure in a building

[Luc]

Hello,

What would be the reccommended water pressure in an institutional building which can accept 60 people? We have a submersible pump in a water tank that feeds three 2'' water pipes. One of the pipes is uses for the D.H.W. heater. The other two cold water pipes go in two different directions. They cover about 150' distance with basement, main floor and first floor.

We had set the pressure switch at about 65 psi. While doing the routine verification the other day, we found that water pressure was over 90 psi. Someone had changed the pression switch setting because there was not enough pressure. Is 90 psi too much? My guess is that the submersible pump could not give enough water and the pressure decrease to 40psi during high demand.

Thanks,
Luc

 

[Valveman]

65 is a lot of pressure for one floor. The more floors you have, the higher the pressure needs to be. It doesn’t do any good to set the pressure switch to 65 or 90, if the pump cannot produce enough water to keep the system at 40 when there is a demand. Flow from the pump must be at least as high as the demand, to be able to keep the pressure up.

 

[Sponsor]

 

[NHmaster]

Tough question and one that to be absolutely sure of the answer you would have to run a bunch of numbers. Problem is, in a commercial building you probably have toilets and urinals with flush valves and they take big volume. And then there's the whole developed length of the water line an branch sizing.

 

[Luc]

Thank you both for the reply.

My main question was to know if the high pressure could damage anything.

Luc

 

[Upper]

Velocities coud reach a level as to have water hammer.Then yes it could do damage...Upper

 

[Rutherfordman]

80 psi is the maximum (plumbing code) you want to have in the distribution system. Greater pressure can cause fixtures to leak prematurely. If you have flush valves in lieu of tank type toilets then they require a greater pressure (27 psi min.) and as I believe was stated more volume (larger water line size).
With decent water pressure (65-80 psi) we can usually feed up to 4 stories without a booster pump. If you have a kitchen with a commercial dishwasher it may require a greater pressure than 27 psi but usually not more than 50 psi.

 

[Luc]

Thanks everyone for the input.
Luc