Jockey Pump in Combined System

[Saber Elkassas]

I working on designing a combined raw/ fire water system. The installed jockey shall be used for raw water supply and system pressure maintenance. The jockey pumps are supplied by a storage tank with 60% fire water reserve.

The main issue here is the case when all the raw water is consumed and only the 60% fire water capacity is remaining, if the jockey pump is kept in operation the users shall consume the fire water reserve as well and if the jockey pump is stopped, the fire water system will not pressurized any more.

So, how to control the jockey to keep the 60% fire water reserve capacity and the system is always pressurized?

 

[LittleInch]

You can't.

Which is why common supply systems like this are not normal unless you can segregate the users, I.e two sets of pipes and two pumps or one pump with an actuated valve on the feed to the raw water system.

Make sure you always have more than 60% in your tank is the only other way.

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