We have a shallow well with a 1/2hp pump, a sand filter and water softner. Our problem started a couple of months ago and seems to be getting slowly worse. Our pump is set at 40/60 and cycles I think ok. The water pressure starts out ok when you turn on any faucet or shower but if you run the water open for more than a few minutes the water pressure drops alot. If trying to use a lawn sprinkler, it will work ok for a few minutes and then the pressure drops low enough that the sprinkler will not function. If using the washing machine it is now impossible to shower or even wash dishes because the water pressure will drop to a bit more than a slow stream. I don't know where to start, can you help me?