My foot valve is at 190' and the venturi is at 160'. Allparts were replaced in the pump and the venturi. The foot valve was changed. I still can not pressure up the system. Max to 20 or 25psi then drops down to 0psi, why? Is there anyway a drop in the water table would effect function of the system?

Not super familiar with these systems, but going down close to 200' is a stretch for a jet pump system. Assuming you have at least a four inch bore, have you considered a submerged pump?

Thanks for the input. I already considered a submersible pump. The jet pump system is 40 plus years old. The pump runs but I believe there is not enough zing to suck up the water at the correct rate. The so called pros I have helping me are in denile and I need some evidence to sway the pros.can a pump suck water at half the rate it once did?

Wish I could be of more help. I would think that a drop in the water table would have an impact, especially if it got down close to the 160' level where your venturi is located. What are the pros saying?