well water pressure/volume question

I am trying to figure out what causes our water to lose pressure. Just using it for the house ie showers washing etc it seems fine but when watering with a hose for a length of time the pressure drops quite a bit. It makes our sprinkler system useless. The work fine for a few minutes then the pressure drops and they wont work.

How can i diagnose this problem. Is our pump to small or does our well water level drop? Or is it some other issues. We dont ever seem to run out of water though.

As you pump, you are lowering the water level in the well. A good pump man can test the recovery rate of the well to determine if a "bigger" pump can be installed without over-pumping the well.

Could be you've pumped the water down to the pump intake level and the pump is only giving you what the recovery rate of the well is.

Pump GPM runs on a curve based on how high it needs to lift the water. When drawing faster than the pump can produce, the pressure drops.