Plumbing – Choosing the right replacement pump for well


I have a 40 foot deep 6 inch drilled well. Currently it has an old 3/4 horsepower jet pump, but it is shedding bits of rusty metal into the return pipe which are getting clogged in the foot valve. Everyone is recommending that if I have to replace the pump, I switch to a submersible, but nobody can say why other than "they are better". What are the actual benefits of a submersible over a jet pump (other than being capable of greater depth which doesn't matter here)? Do I need to get a 3/4 HP submersible, or would a 1/2 be fine since they say they do 12+ GPM at 40 feet?

Best Answer

Jet pumps were a great idea when pump motors were terribly unreliable, and you could keep the pump motor out of the well by using one.

These days, that's not true. Likewise, anyone who recommends a "3-wire" submersible is also living in the past. Things have changed. I'd suggest a 2-wire pump (there are 3, but one is the ground, and not counted as per usual - "3-wire" pumps use 4 wires for the same reason.) 3-phase is a different deal and un-applicable to most folks with individual water wells. Personally, I prefer a stainless steel pump.

Advantages of a submersible pump other than greater depth capacity -

  • much more power efficient - you pump the water once, that is it. You don't pump a lot of water around in circles to pump less water out of the well, which is roughly what a jet pump does.
  • You don't need to prime it. So much simpler. Drop it in the well and apply power, out comes water.

If they made them, you could probably use a 1/4 HP pump on that well. Last time I was shopping pumps, 1/2 HP was the smallest they made. You may need a restrictor valve (or orifice/plate) to keep it happy.

In the same counterintuitive manner that fans draw LESS power when restricted, non-displacement pumps also draw less power when restricted, and can draw too much power if unrestricted with low head. The short and simple explanation is that it's doing more work (moving more water) when un-restricted, and doing less work (moving less water) when restricted. Most people not already aware of this won't believe it until it is demonstrated with an ammeter and a valve.

Likewise, if your well can't keep up with 12 GPM you'd want to restrict the pump for that reason.