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jorge54 · May 18, 2010, 06:15 AM

I can't find a pump with 18 lps capacity, 4 - 5 bars at 80 meter head, so pump suppliers is giving me a pump with capacity of 18 lps at 80 meter head but with a pressure rating of 12 bars. So in order to use this pump, I want to have a PRV installed after the discharge line. Is this possible and how much distance from pump discharge line for the PRV to be installed which is allowed for the pump to operate properly.

Widdershins · May 18, 2010, 03:21 PM

I'm not sure I understand why it is you want to reduce the pressure.

Exactly what is the application here?

jlisenbe · May 18, 2010, 04:23 PM

12 bars of pressure converts (according to the internet) to about 175 psi. That's a lot of pressure, not to mention 18 liters per second being a fairly good deal of volume, so I'm assuming this is not for a residence. And, since you want to reduce the pump's pressure, I'm going to guess you are not pumping into a pressure tank. So, as Widder asked, what is the application?

jorge54 · May 18, 2010, 08:52 PM

Originally Posted by Widdershins

I'm not sure I understand why it is you want to reduce the pressure.

Exactly what is the application here?

The application is a combination of domestic and fire water line. Existing installation of fire pump which was used for fire water line and domestic water line. Before the jockey pump was working as domestic water supply and the jockeey pump was worn out. I want to replacee the jockey pump with a booster pump in line with the fire pump. The problem if they are operating in parallel, there come a point that the operating pressure is up to 12 bar when the fire pump starts. I could not separate the two system now, so I planned to replace the defective jockey pump with a booster pump.

jlisenbe · May 19, 2010, 03:48 AM

Jorge, I have no idea what a "jockey pump" is, but if you are referring to a two pump system, one for fire and one for the home, and they are installed in parallel, which is to say independent of each other, then how will the operation of the fire pump influence the residential pump? You would simply install a check valve before each pump, which would prevent any backpressure from one pump to another. Is that what you are referring to?

Booster pumps are generally installed in series, which is to say they take water already under some pressure and "boost" that pressure higher.

I'm still not just real clear what you are after here. Are you pumping from a well (That's what is sounds like.) or are you coming off an existing municipal water line?

jorge54 · May 19, 2010, 05:51 AM

The system is that the whole water system for sports complex, fire and domestic water is being pumped out be fire water pump with a jockey pump. The jockey pump serves the doemstic water requirement and the fire pumps runs when pressure runs low when fire water demand is needed for the fire fighting line. Now, the jockey pump has been worn out and instead of changing the jockey pump, I want to replace it with a booster pump composed of duty/stand by. The problem, whenever the water demand requires the fire pump starts and lots of breakages along the line. Fire water pipe lines uses UPVC with a pressure rating of 16 bars. Due to old installations, more than 10 years already, whenever the fire pump starts, breakages occurs. I intend to install a PRV but it defeat the purpose because the selected replacement booster pump has a pressure up to 12 bars. Domestic operating pressure is only from 3 - 4 bars.

Widdershins · May 19, 2010, 07:02 AM

Originally Posted by jorge54

I intend to install a PRV but it defeat the purpose because the selected replacement booster pump has a pressure up to 12 bars. Domestic operating pressure is only from 3 - 4 bars.

How is the domestic/potable side of the system protected from siphonage from the fire suppression system?

Is there a Reduced Pressure Backflow Preventer or Double Check installed?

As for the CPVC fire piping, most municipalities require the piping to be able to withstand a 200psi static test -- This is not its normal operating pressure, by the way, just a test to ensure it can withstand pressure surges.

Without actually seeing how the system is put together, my gut tells me you do likely need a PRV installed on the discharge side, but depending on local requirements, you may also need a second PRV installed on the fire suppression system.

jorge54 · May 19, 2010, 08:58 PM

There are PRV going to each toilet but our site engineers are afraid to run the fire pump in auto mode. So, I decided not to install a PRV right after the booster pumps which has a head pressure up to 12 bars. I instructed them to install the selected booster. Pumps with pressure switch, Double backflow preventer or double checck valve are installed after the fire pumps.