I am purchasing a small "high pressure" centrifugal water pump to run some irrigation sprinklers.
I have a 20' tall hill overlooking a flat that will be irrigated. I have a water tank up on the hill.
Assuming line loss is not an issue, would the pump have to work harder if it were placed at the tank, or the bottom of the hill?
With pump at top of hill:
Pressure at pump = 53 psi
Pressure at sprinklers = 60 psi
With pump at base of hill:
Pressure at pump = 61 psi
Pressure at sprinklers = 60 psi
The pressure difference at the pump is caused by the elevation difference (20' x .43 psi/ft)
The difference is probably minimal and this is more for discussion purposes.
Line loss shouldn't be an issue, unless you run through a series of 90å¡ pipes. Seems to me that the pump is working the same at the top or the bottom.
It appears that the pump is simply adding say 53 PSI at what ever location it is placed.
0 psi at intake +53 psi from pump + 8 psi from gravity = 61 psi at sprinkler
8 psi from intake gravity + 53 psi from pump = 61 psi at sprinkler.
So if you took that to the extreme and had say 50 psi from gravity (instead of 8), does the pump have to work any harder to go from 50 psi to 103 psi rather than 0 psi to 53 psi at the top?
Forgive my ignorance, I know very little about fluid dynamics.
I wonder if the pump would even function properly under 50 psi intake?
OK - so I got a response from an engineer at Honda. They said that that the pump would have the same load either way. However the pump parts are only rated for 55 psi, so it would be better to place the pump at the tank to reduce the pressure that the seals are subject to.
So in my extreme example, it is clear that the pump should not be placed at the bottom of the hill where it would be subject to the additional gravitational pressure.
EDIT: They also said that the pump would be under very little load either way because it is only running a few sprinklers. Looking forward to getting this pump (WH15 Honda).
