How to determine the Booster pump size for irrigation system

[Saad]

Hi Pros,
I purchased 7 oscillating sprinklers for my back yard and would like to buy a booster pump for my irrigation system to avoid any low pressure or malfunctioning of the system knowing that I will be turning it on automatically after midnight in order not to affect the house water supply.
I have attached the diagram showing everything needed to determine the required booster pump.
So, i would really be grateful if someone could have a look at it and help me select the right pump (e.g. produce XX GPM and required peak flow at XX feet)
Thank you in advance

 

[Valveman]

It won't matter how large a booster pump you have if the well pump cannot supply enough to start with. And if the well pump can supply enough, you most likely do not need a booster pump. How large is the well pump?

 

[Sponsor]

 

[Saad]

It won't matter how large a booster pump you have if the well pump cannot supply enough to start with. And if the well pump can supply enough, you most likely do not need a booster pump. How large is the well pump?

Hi Cary,
Thank you for your replay.
The current well pump like you said will most likely have to be replace, the current one is at 12gpm and 1/2 HP. So, Knowing that the pressure tank is set between 30-65PSI, I'm planing to get a new well pump with 27GPM and 1 HP. Should I do so and knowing all of the given factors, what's your advice on the required booster pump please?
Thank you
Saad

 

[Valveman]

If your water level is less than 10' deep, a 25 GPM, 1HP pump will produce 25 GPM at 60 PSI. You won't need a booster pump. If your water level is deeper than 10', or your irrigation needs more than 25 GPM at 60 PSI then you need a larger well pump than 1HP, but still not a booster pump.

 

[Saad]

If your water level is less than 10' deep, a 25 GPM, 1HP pump will produce 25 GPM at 60 PSI. You won't need a booster pump. If your water level is deeper than 10', or your irrigation needs more than 25 GPM at 60 PSI then you need a larger well pump than 1HP, but still not a booster pump.

The water level is around 3'. In that case, and given all the factors I put in the initial design (7 Oscillating sprinklers @4.62GPM each, lenght of hoses...) what well pump should I buy then? I mean the required GPM and PSI please?
Thank you very much

 

[Valveman]

7 X 4.62 is 33 gpm. Will your well make 33 gpm? If so, you will need about a 1.5HP pump. But you don't have to run all 7 at the same time?

 

[Saad]

7 X 4.62 is 33 gpm. Will your well make 33 gpm? If so, you will need about a 1.5HP pump. But you don't have to run all 7 at the same time?

We will run 4 sprinklers at a time and 3 others later as we have a programmable irrigation system. so, in that case we will have 4x4.62 is 18.48 GPM. I will check with the guy who digged the well if it will make 18gmp. Other than that, the length of hoses doesn't matter? if the sprinklers will need 18.48gpm, then what is the recommended well pump specs (GPM and HP) please?
Thank you

 

[Valveman]

A 3/4HP in 18 or 20 GPM series will do 18 GPM at 50 PSI. However, when you only use 3 sprinklers the pump will cycle on and off, which isn't good. You will either need to make every sprinkler zone 18 GPM or use a Cycle Stop Valve to keep the pump from cycling when using less than 18 GPM. Then when you have a CSV, you have more choices of pumps. You could even use that 1HP, 33 GPM, Hallmark pump, which is way less expensive than any other pump I can find that will do that job.