# Booster Pump?



## Rix (Jul 25, 2017)

We've been renovating a 6-story office building, including some additions to the first floor, for over a year. City just told them to install a backflow before they could close out the building permit. We installed it and the pressure on the 6th floor dropped from an already low 35psi to 25 resting. The original master of the job, my old boss, said we could possibly put a pressure tank on the 6th floor. I want to give the building a quote on having a booster pump installed. The owner of my company, an a/c guy, wants nothing to do with it. I'm curious as to what problems the low pressure would create...I know the flush valves need about 35 psi to operate properly (there are 4 per floor) 

I know this seems crazy but this was a building from 1968 and the engineer definitely did the building owners a disservice on multiple accounts. And the plumbing has been grossly neglected by the owners and even my own company...we had all the chillers, and duct work installed before I ran one water line. Oh and the master who quoted the job left the company in may. 

Looking for advice because we just ran into this Friday and my owner comes back from vacation tomorrow. I'm under the impression than a booster pump can be set to increase the pressure about 20 psi throughout the building which would give us about 75 on the 1st floor and 45 on the 6th. The 1st floor has about 40 fixtures and then floors 2-6 are identical with 1 hose Bibb, 1 kitchen sink, 1 urinal, 1 mop sink and 3 WCs. I don't know their usage as they are only just now getting to capacity. The incoming city pressure is roughly 58psi. 

Thank you.


----------



## GAN (Jul 10, 2012)

The design on the original was lacking. Consider your water tower supplying the building would need to be about 30 feet or so above the top floor to provide 45 or so PSI at the top floor.

Projects like this pump the water up to the top floor to a holding tank if the building is of any size, then let water fall down to provide pressure with pressure reducing valves on the lower floors to get by without pumps.

You pressure loss across the backflow preventer will be around 10 PSI, so as you stated limiting the pressure right out of the box. If you do add the booster pump I would do it after the backflow preventer so you negate the loss of pressure across the springs. You could then (if you isolate each floor) install a PRV to even out pressures in case a large volume is needed on the first floor you won't get as bad a pressure drop on the top floor.

Outside of required pressure for flush valves to operate in Illinois your only really required to provide 15psi at a device. They may not like it but it would be code compliant, of course at these low pressures flush valves, etc. will be affected and you start getting your complaints.


----------

