I could write a novel on this but I will try to keep it short.
I have recently been trying to help a friend with some irrigation issues. His pressure really sucked, I guessing 25psi max. He ran a 1/2hp centrifugal pump 50 foot from his 110ft deep 2" well. A 1" suction line was used for the entire length pump to well, then dropped 40' with a check valve screwed on the end. So here is what I have done and results..
1. Installed a new(slightly used) 1 1/2hp centrifugal pump.
*Results were about the same, if not worse.
2. Ran a 2" suction line from pump to well. Added 2" check valve @ top of well, then ran a 1 1/4" drop line 30' down well w/no foot valve. (All in an effort to reduction section head).
* Pump cavitates pretty bad, psi fluctuates between 8 to 30 psi. I can get it to level out somewhat by regulating discharge with a gate valve on the discharge line, putting the pressure at the pump about 30 psi, but much less in the field. Also, if I stop all discharge flow, the pressure at the pump will never rise over 30.

Is the pump just not getting enough water? Could it be too much suction head still?? Resting water level in the well was @ 10 ft below ground. I am not sure if it is drawing down while the pump is running and if so at what rate. I dont believe to suction line should be much of a restriction anymore now that the size is much bigger. Not sure where to go with this. Any help or thoughts would be much appreciated. Thanks.

 

Water at 10' is no problem. Water at 20'+ when pumping is a problem, and is probably what is happening. If that is the case, you need a two pipe jet pump or bigger casing so you can use a submersible.

 

I think your right, its 10' static @ rest, but I have no idea how much it draws down while pumping. I guessing a lot. Our water tables are rediculously low right now, I am wondering if it is something that will improve once we get some rain (if ever). Was thinking of getting w/ a well guy I know of and asking of there was anything he could do short of digging a new well. Thanks for the response.

 

if pump is cavitating, i'd bet u have a suction leak or two that you arent aware of. a check valve up top will work fine if everything is tight, but a 1.25" foot valve 30' down the well on the bottom of the drop pipe would be my choice for best results (especially longterm) in a 2" well.. and if you replaced a good cast iron 1/2 pump with a cheap plastic 1.5... you probably didnt help much (not saying u did, but i see it alot).

just fyi, i happen to be a direct descendant to original florida cracker cowboys in NE florida. (in case of any confusion, they were the guys that "cracked" the whips while running cattle through the florida swamps).

 

while I cant say 100% that there isn't a suction leak, I am pretty darn sure I do not, I have been over it a multitude of times because it is what I originally thought was the problem. I am really thinking the well just cant keep up with the demand. I was going to put a vacuum gauge on the suction line (as soon as i get one) and see what it reads. I think someone told me it should'nt read over 15lbs?? or I have a problem. If it does I think this would confirm too much draw down. Only one other variable I can think of at the moment. Does the top of the 2" well need to be airtight where the drop pipe is inserted?? This one is not.
As for the pump, the .5 was a goulds, however the new(er) 1.5 is a sta-rite, which I believe to be pretty good,not some cheap H.D. model.
As far as the florida cracker goes, you taught me something new, I just picked it as the first name off the top of my head.
Thanks for the reply.

 

sta-rite is a good pump. i cant see where the output should be fluctuating. even if the well couldnt "keep up".. with the 30' drop pipe installed, the pump should pull the water level down to 25 or so, then pump a steady stream of whatever the well will make.

i think u got other problems.... suction leak my guess. easy to do with all those 2" connections and fittings. if you really wanted to increase volume you coulda ran a wire in the ditch and hooked the pump up at/by the well.