new pump jet vs. sub

I am plumbing in a cistern on a sloped site. Our cistern is slightly below level to the house. The house is built on poles, 1st floor 8ft above grade at high end where the plumbing enters the house. (In hindsight, would have put the plumbing at the other end of the house, just stuck with layout). I found in a post in this forum that the supply line cannot slope up and down with a jet pump.
So, the pump I have currently plumbed in will not prime. It is a 1/2 hp jet/tank system. My supply line drops approximately 8ft over a 50ft run before running straight up 8ft to the pump. Would I be better off with a submersible in the cistern? Any other advise?

Submersible pumps are more reliable and more efficient. A 1/2 HP submersible will provide pressure and flow like a 3/4 HP (or in some cases a 1 HP) jet pump. However, they also cost more than a jet pump.

If you buy a submersible you should find one where the pump is matched to the pressure requirement of your system. Most submersibles off the shelf in a Big Box store are for moderately deep wells and will provide more pressure and less flow than a properly sized submersible for your application.

The suction line of a jet pump should not run up then down because it will almost always get an air bubble at the high spot. You can eliminate that with a lot of trouble but it is not reliable.

The suction line down then up is a different situation. IF THE AIR CAN ESCAPE AT THE INLET END it is possible to get reliable operation if the suction pipe goes down first, then up, because the air can escape at both ends. If I had that situation with a jet pump from a cistern I would put the check valve at the pump rather than as a foot valve in the cistern.

Even though the pipe runs uphill your pump will still prime. It just won't prime easily.

The submersible is the best way to go. The 1/2hp sub will cost more than a 1/2hp jet and only a few bucks more than a good 1hp convertible jet pump with the bolt on jet. But you will still be happier with the 1/2hp sub, for many reasons.

Compare prices at these two sites.
Submersibles

Convertible Jets

bob...

Thanks for the info. I am looking into sub pumps and I am enjoying all the debate about CSVs. Hopefully it solves the problem. I'll update when I have a chance to do something (hopefully soon).