Jet Pump loses prime overnight

I have an old sandpoint well (unknown depth) with a 25' 1 1/4 in pipe. (There is no casing...just the driven pipe.) The static water level is at 12 feet. I don't know if there is a foot valve. I have replaced an old 1 HP Fairbanks pump with a new Flotec 1 HP convertible jet pump. The new pump has a check valve built into the jet assembly attached to the pump. The pump works fine all day when used for the house or general irrigation....but loses prime (or suction) overnight. The pressure at the pump is the same in the morning as it was when we went to bed......but in the morning...when it drops to the cut in level (currently set at about 32, it doesn't draw water. It just starts using from the pressure tank (28 pounds above bladder)...and pressure starts down from there. All it takes to re-set it is (to draw water again) is to flip the power to the pump off...and then back on. I have tried every combination I can think of. My best guess is very small holes in the suction pipe between the water level and the pump...but I've even tried a smaller pipe down the main pipe (with its own foot valve)...and it still does the same thing. Thanks in advance for any help.

 

I would guess that you have small holes in your pipe. How old is your pipe?
You must be getting air somewhere.
I assume you have a well point screen on the bottom, so you would not have a foot valve. The check valve is above ground at your pump.
Vey can give you much more info, as he knows more about these shallow wells. Hopefully he will see this post.

 

"The new pump has a check valve built into the jet assembly attached to the pump."

In the jet assembly? Or in the pump? If it is the pump, it is probably crap. If so, you should put in a real check valve, preferably brass. The plastic ones are pretty crappy, too.

It is pretty easy to check foot valves (valve at the bottom of the well) by just disconnecting the pipe from the pump, fill the pipe with water, leave over night and check in the moring. If the water level has gone down, the foot valve is leaking.

 

And if you think the pipe has leaks, then fix 'em.

 

Thanks for your help. I don't believe that there is a foot valve...but I've put an additional check valve in-line behind the pump (which has its own check valve)........and it still loses its prime overnight........or in just an hour or so. The water level in the well is at 12'. I can't find any suction loss above ground. The pump check valve seems to operate fine...but what if.........? I may be all wet (pun intented) and I'm probably over-analyzing this mess....but I'm at my wits end! Please bear with me. ** If there are small holes in the well pipe between the 12' water level and surface (I can't just pull this out and check it. It's been in there about 50 years and I'm afraid of what I'll get into without help) and the water escapes ...dropping the water level down away from the check valve (or valves)....and the water pressure on the output side is still between 30 and 50 lbs.....wouldn't the check valves be in the open position? If this is the case...and the water level has fallen on the suction side....when the pump comes on.....would the valves be partially open...with an air gap behind them (on the well side).....so there's no suction to pull that water? I guess the valve would have to leak water back into the well pipe slower than the water level recedes in the pipe....and then... When I turn the pump off.....the valves close tighter because of the reduced pressure....and a new vacuum is able to form.....bringing up the water again. Is this possible. My wife thinks I need adult supervision. She's probably right.
Of course I'm looking for an easier (cheaper) answer. Ha. Thanks again.