Hi, I had a 1/2 hp convertable jet pump at my cabin for 18 yrs. I have a shallow well with a max depth of 10ft from ground to bottom of well. Pump is in my camp about 4ft above ground level. Recently my pump would kept running and would not shut off unless I cut the power to it. Never had an issue with the system before. I changed the pressure switch which was 20/40 to a 30/50. (the only one I could buy) I readjusted my pressure tank up to 28 lbs when empty. Pump would still keep running so I took the end off of my the pump and made sure the nozzle and venturi were clean. This also made no difference. I decided the pump must be at fault so I replaced the pump with a new 1/2 hp shallow well jet pump. Now I can still only get pressure to build to 43lbs. I have replaced the foot valve on my "older" 1" underground PVC waterline with a new 1" one. This line has a pitless adapter on it at the well. Still no difference. I purchased a new 1" PVC line and new foot valve which I just dropped into my well. Still no difference in the amount of pressure. My old pump had a 1" inlet on it, my new pump has an 1 1/4" inlet on it which I have reduced down with a metal bushing to accept a 1" waterline and it has a 1" outlet. All of the plumbing guys who I know that does this work for a living tell me that's acceptable and should not affect the operation of the pump. It is a single line from the pump to the pitlass adapter/well, a distance of about 60ft. I have replaced the seal on the adapter. Once I cut power and read my pressure gauge, the pressure holds which tells me there is no leak in the system. I can shut off the main line in my cabin about 10ft away from the pump and there is no leaks from the pump to there either. Also as I mentioned I have tried it with a brand new suction line with same result. Here is a link with the specs of the new pump. Its called a Little Giant. 1/2 hp wired for 115v http://littlegiant.com/media/130632/995259.pdf My old pump is a GSW CJC50 313501(313 series)(501 1/2 hp) Why does my pump not reach cutoff pressure?