Tap off of domestic water in place of jockey pump

[jar546]

I always see and am accustomed to inspecting jockey pumps for fire sprinkler systems. I’m starting to see more situations like this that are existing where they are tapping off of a domestic line 2 the fire sprinkler system in lieu of a jockey pump. Do you see this often? Is this an approved method?

 

[e hilton]

Does that go to a pump, or are they relying on domestic pressure to provide enough flow?

 

[Yankee Chronicler]

Without opening any code books to verify, my recollection is that tapping the domestic water supply is only allowed for NFPA 13D systems and for limited area sprinklers systems.

 

[jar546]

Does that go to a pump, or are they relying on domestic pressure to provide enough flow?

No jockey pump. In place of the jockey pump is the domestic water pressure of 52psi,

 

[TheCommish]

Is the 52 psi sufficient to keep the system at pressure to prevent the main pump from coming on unnecessarily? Keep in mind that jocky pumps do not have to be fire service rated, if and when th3 jocky pump fails the main pump will come on and bost the press and should keep running until shut off manually.

 

[e hilton]

Is the 52 psi sufficient to keep the system at pressure to prevent the main pump from coming on unnecessarily? Keep in mind that jocky pumps do not have to be fire service rated, if and when th3 jocky pump fails the main pump will come on and bost the press and should keep running until shut off manually.

I read it as there is no pump. No jockey, no main. Only city pressure.

 

[Yankee Chronicler]

I don't have a current copy of NFPA 13, but I doubt the water supply requirements have changed much. Regardless of how water is supplied to the system, it has to provide sufficient pressure at the head with the highest elevation, and it has to supply sufficient volume to satisfy the hydraulic demand based on the number of heads required for the hazard. This is from an older copy of NFPA-13:


Jockey pumps, in my experience, are usually used to supplement either pressure or volume. I don't see how tapping off a domestic water line would increase either pressure or volume, so it would seem that tapping off the domestic line isn't so much to avoid a jockey pump but rather to avoid running a separate sprinkler main.

 

[Yankee Chronicler]

No jockey pump. In place of the jockey pump is the domestic water pressure of 52psi,

52 pounds measured where? What's the rise (and pressure loss) between the point where the 52 psi is measured and the highest head, and what pressure does the specified head require?

 

[TheCommish]

The function of the fire pump, not the jocky pump is to bost pressure so then most hydraulically challenge or furthest sprinkler demand has sufficient flow and pressure to deliver the need sprinkler density. The function of the jocky pump is to maintain the desired system pressure so the main line pump does not run to make up slow pressure loss.

If street pressure and flow is sufficient to supply the design area adequately you don't need a jocky pump.

 

[jar546]

The function of the fire pump, not the jocky pump is to bost pressure so then most hydraulically challenge or furthest sprinkler demand has sufficient flow and pressure to deliver the need sprinkler density. The function of the jocky pump is to maintain the desired system pressure so the main line pump does not run to make up slow pressure loss.

If street pressure and flow is sufficient to supply the design area adequately you don't need a jocky pump.

Yes, if the pressure is too low, the fire alarm panel lets us know.

 

[TheCommish]

JAR, I haven't look, however I don't think the set up would be prohibited

 

[e hilton]

JAR, I haven't look, however I don't think the set up would be prohibited

Does the designer of the sprinkler system have calcs that show the min required psi and gpm? Can the archirect show that the city water supply meets that?

 

[TheCommish]

NFPA -20, 2025 edition