Sprinkler Pump: 10 GPM @ 30PSI (seem low?)

[Tomas]

I have a Myers 1.5HP well pump for my sprinkler. It's about 10 years old. Sitting outside in the elements, I cannot read too much on it anymore. Seems to me that 10GPM is extremely low. Is it and if so, could it be due to the pump being old? Could it be due to the well - not supplying enough water. I'm in central Florida if that matters and no rust from the well water. I have no idea how deep it is. It looks like it's being fed with a 2" pipe.

Pressure and GPM were measured just after the pump out of a 3/4" opening. It took 29 seconds to fill a 5 gallon bucket. 30PSI was measured from the same spot. Although, 4 sprinkler heads were "spraying" water down at the end of the run if that matters.

On a side note, it ran at least a couple of times for a few hours without water - lost its prime somehow. It still functions though.

[Gil]

To determine the pump's capacity you need to take a few things into consideration. For example, the 30 psi you mention - was it taken from the discharge side of the pump? If so, it would be the pump's 'residual pressure' with a flow of 10 gpm. If this is the case, then the pump is still capable of a higher gpm flow. You could try using two discharge points of the same size and note the residual pressure while flowing. As the pump reaches its gpm capacity the residual pressure will start decreasing and the water being discharged will be considerably more.

From what you described I would think your pump is capable of pumping considerably more than 10 gpm. All you have done so far is determine that the pump is capable of pumping 10 gpm through a 3/4" outlet with a residual pressure of 30 psi.

Keep in mind that the 'residual' 30 psi pressure is not the flow pressure. There are other factors such as the depth the pump has to draw the water up from, the distance from the pump discharge to the outlets, the number of elbows or right angle turns that may be in the line feeding the outlets, etc.

[Tomas]

All measurements were taken on the discharge side (see arrow on pic). I have an existing sprinkler system that is about 10 years old and failing (poor coverage from original design). I'm filling out a design sheet from Rain Bird and calculated PSI and GPM per their instructions. I currently have 4 zones setup, but I think my yard should have 5 (125' X 80' lot). At the end of the day, I may need an new system installed so I'm trying to work this out before I send in the paperwork to Rain Bird. I don't want to end up with a band-aid - I want a nice functional system.

[Tomas]

All measurements were taken on the discharge side (see arrow on pic). I have an existing sprinkler system that is about 10 years old and failing (poor coverage from original design). I'm filling out a design sheet from Rain Bird and calculated PSI and GPM per their instructions. I currently have 4 zones setup, but I think my yard should have 5 (125' X 80' lot). At the end of the day, I may need an new system installed so I'm trying to work this out before I send in the paperwork to Rain Bird. I don't want to end up with a band-aid - I want a nice functional system.

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[trader4]

You think just maybe the water that was flowing through those 4 sprinkler heads should be counted into the flow rate?

[Tomas]

Yes, actually, I had considered that. The new measurements are 35PSI and about 12GPM, which is a bit better and might still be suitable for my needs.