How to Set Jockey Pump Shutoff Pressure?

2/10/2022

Hi everyone - I need advice about jockey pump sizing.

The system we have has a city supply plus a booster pump. The city main shut-off pressure is 42 psi (2.9 bar) and the booster pump shut off pressure is 27.5 psi (1.9 bar).

So, combined, the pressure is 69.6 psi (4.8 bar).

The jockey pump pressure should be about 10 psi (0.7 bar) higher than the booster pump pressure. So, the jockey pump shutoff pressure should be 27.5 psi + 10 psi = 37.5 psi (1.9 bar + 0.7 bar = 2.6 bar)?

Is this correct, or is the jockey pump shutoff pressure the combined 69.6 psi + 10 psi (4.8 bar + 0.7 bar)?

Thanks in advance.

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12 Comments

Nick D

2/10/2022 08:17:09 am

Your jockey pump stop pressure should be set at 69.5 psi. This is based on:
maximum city supply + rated pump shutoff pressure

You would want your jockey pump to start at 10 psi lower (59.5 psi) and then you fire pump to start to start 5 psi lower than that (54.5 psi).

Of course this is just best practice, but has worked for me in the past.

Glenn Berger

2/10/2022 08:17:19 am

See NFPA 20 A.14.2.6 (4)(f) for additional information. The pump starting pressure should be 10 psi different, not the stopping pressure.

Colin Lusher

2/10/2022 09:32:15 am

Nick is correct:
Jockey pump stop should be 69.6 psi.
Jockey pump start should be 59.6 psi.

Main pump stop should be 69.6 psi
Main pump START should be 54.6 psi, however, it's not uncommon to drop that another 5 psi to 49.6 psi (10 psi below JP) if you have trouble with the main pump starting during normal day to day pressure fluctuations.

Alex

2/10/2022 09:37:26 am

Nick outlined the requirements well above.

For a code outline of start and stop points, refer to NFPA 20 (2016) A.14.2.6 (4)(f)

Jesse

2/10/2022 09:38:13 am

Hopefully this helps from 2016 NFPA 20 A 14.2.6 (4)

(4)
Fire Pump Settings. The fire pump system, when started by pressure drop, should be arranged as follows:

(a)
The jockey pump stop point should equal the pump churn pressure plus the minimum static supply pressure.

(b)
The jockey pump start point should be at least 10 psi (0.68 bar) less than the jockey pump stop point.

Franck

2/10/2022 11:07:53 am

All the above mentioned settings are correct.
It looks like there is a confusion in wording in your question.
What you call city water shuttoff pressure is probably the static pressure of the city water.
And what you call booster pump shutoff pressure is the churn pressure (pressure delivered at no flow).
While the booster pump shutoff pressure is the pressure at which your jockey pump should stop. In other words, the pressure you need to maintain in your sprinkler system downstream the booster pump.

Franck

2/10/2022 11:27:38 am

Just a correction to my message (this is what happens when you answer with your phone, sorry for that…) for the last sentence
You should read :
« While the Jockey pump shutoff pressure is the pressure at which your jockey pump should stop ».

The purpose of the jockey pump is to maintain a pressure in your system close to the pressure that will be delivered when your booster pump will start.
The different settings (difference of 10 psi and then 5 psi) is to limit a possible waterhammer effect when the booster pump starts (which could happen if the fire pump starts at a very low pressure compared to the one that will be delivered by the pump).

Jake

2/10/2022 11:52:33 am

Hi! I am glad that the issue sparked a debate.
English is not my native language so some of the terms may be wrong. thank you for correcting.

So when the static pressure of The City Water is 2.9 bar and the booster pump churn pressure is 1.9 bar. Compined 4,8 bar.

And same static pressure of The City main
affects to the Jockey pump so 2,6 bar churn IS enough for it? Compined (2,9+2,6) 5,5 bar.

Theres no need to calculate IT like this:
Static pressure of The City Water+ Booster pump churn+ static pressure + 0,7 bar..

Franck

2/11/2022 10:43:30 am

English is not my native language as well ;)

Jesse

2/10/2022 02:25:05 pm

Thanks for the clarification. I kinda wondered about the "shutoff" comment too.

HAHANE AROMA

5/22/2023 11:12:42 pm

Should the jockey pump be left on manual switch on/off. The property owners that I am dealing with have always been switching the pump on when they see the pressure is low and switch off when the pressure reaches the level they have marked.

Please advise if this is OK.

lalith ramachandra

4/28/2024 07:58:17 pm

Given that water is incompressible, as soon as a hydrant is opened, the water pressure in the whole system will drop to the standing pressure?

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How to Set Jockey Pump Shutoff Pressure?

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