Where each one physically sits
A submersible is a long skinny cylinder, about four inches across, that hangs on the end of the drop pipe hundreds of feet down inside the casing, underwater, all the time. Motor on the bottom, a stack of impellers above it, everything sealed at the factory and cooled by the water flowing past it. Power reaches it through a submersible cable strapped to the pipe. It pushes water up the pipe, out through a pitless adapter in the side of the casing below the frost line, and down the buried line into the house.
A jet pump is the other layout entirely. It lives in the basement or a well house, bolted to a stand or sitting right on top of the pressure tank, and you can walk up and put your hand on it. It's an electric motor with an impeller and a venturi in a cast housing, and it moves water by creating suction on a pipe that runs down into the well. Nothing of it is underwater.
That one structural difference drives everything else on this page. The submersible is out of sight and out of reach. The jet pump is in front of you with a screwdriver's worth of access. Every tradeoff in cost, noise, efficiency and service comes back to that.
The depth limit that settles the question
A pump can't suck water up past a certain height, no matter how good it is, because it isn't really pulling. It's lowering the pressure at the top of the pipe and letting atmospheric pressure push the water up. At sea level that ceiling is about 34 feet of water column, and by the time you account for friction, fittings, a foot valve and elevation above sea level, the practical working limit for a shallow well jet pump is around 25 feet of lift. Not 25 feet of well depth. Twenty five feet from the pump down to the water surface while the pump is running.
Manufacturers got around that with the deep well jet. The ejector assembly, the venturi and nozzle that create the suction, gets moved down into the well instead of living in the pump housing. Two pipes go down the well: one carries pressurized water down to the ejector, the other carries the combined flow back up. Putting the vacuum down near the water instead of up in the basement extends the reach to somewhere in the range of 80 to 120 feet, depending on the pump and how much flow you're asking for. Output drops off hard as depth increases.
A submersible has no lift limit in that sense, because it never lifts anything by suction. It's underneath the water pushing up, and how deep it can go is just a matter of picking a pump with enough stages for the total head. Setting one at 400 or 500 feet is routine work. That's the practical dividing line: if the static water level is more than about 25 feet down, a shallow well jet is out, and past roughly 100 feet a jet of any kind stops making sense.
Why nearly every deep rock well up here is submersible
Drill through the till into fractured gneiss in this part of New Jersey and you're going deep, because water in fractured rock comes from whatever fracture zones you happen to hit. Wells of 300 to 600 feet are ordinary, and the static water level is often 40 to 100 feet down before the pump even starts drawing. Once it does draw, the level in the casing falls further, and on a low yield well it can fall a long way.
That kills a jet pump twice over. The lift is beyond what suction can do, and the drawdown during a shower would break prime even if it weren't. So the deep rock wells get submersibles, and it isn't a preference or an upsell. It's the only pump that works.
Jet pumps are still out there, and there are plenty of them. They live on shallow wells: older dug wells, driven point wells in the sand and gravel valley fill, spring boxes, and shallow bored wells near the lakes where the water table is close to the surface. Those are legitimate installations that have run for decades. They just aren't what a modern drilled rock well gets.
The honest tradeoffs, in both directions
The jet pump's real advantage is access, and it's a bigger advantage than people credit. It's in your basement. A tech can hear it, feel the housing temperature, check the prime, watch the pressure gauge move, swap an impeller or a seal or a whole pump without a truck full of pipe handling gear. A jet pump replacement is a couple of hours and is the small end of pump work. Diagnosis is mostly free because everything is visible.
A submersible's advantages are that it's quiet, it's efficient, it doesn't need priming and it doesn't care about the weather. You never hear it. There's no motor cycling on and off under the kitchen floor, just the pressure switch clicking in the corner. It's also more efficient in the real sense that you pay for: no suction losses, no water recirculating down and back up an ejector, and multistage impellers doing the work in the direction they're good at. A deep well jet is the least efficient of the three arrangements by a wide margin, and on a house that runs a lot of water you can feel that in the electric bill.
The submersible's cost is that pulling it is the whole job. Nothing can be checked without bringing several hundred feet of pipe, wire and pump out of the ground, which takes a rig or a hoist, two people, and space in the yard to lay it out. That labor is roughly half the invoice on a deep well, and it's the same labor whether the fault turns out to be a cheap check valve or a dead motor. That's why we replace pump, drop pipe and wire together on an old deep well. Paying for the pull twice is the expensive mistake.
Jet pumps have their own costs, and they're the daily kind rather than the occasional kind. They're loud, and if the basement is under a bedroom you'll know every time somebody flushes. They lose prime, which means no water until someone primes it back. They're exposed to a cold basement or an unheated well house, so they freeze. And the foot valve at the bottom of the suction line is a wear part that's just as far down the well as any submersible.
Lifespan, and what actually kills each one
A submersible in decent water runs 8 to 15 years, and we pull plenty that went longer than that. A jet pump goes 8 to 12. The gap isn't about build quality. It's that a submersible operates in a stable environment at a stable temperature with constant cooling, while a jet pump lives through basement humidity, temperature swings, dry starts and the shock of losing prime.
What kills a submersible is short cycling from a waterlogged pressure tank, running dry when a low yield well is pumped down, sand chewing the impellers, a lightning surge coming down the well wire, and low or unbalanced voltage cooking the motor windings. Most of those are preventable, and most of them are somebody's install decision rather than bad luck. A pump set too close to the bottom of the well eats sediment for its whole life.
What kills a jet pump is a leaking foot valve or a pinhole in the suction line that lets it lose prime and run dry, a clogged ejector nozzle, worn impellers and a shot mechanical seal that starts dripping onto the motor. Almost all of that is repairable in place for a few hundred dollars, which is the point of having the pump where you can reach it.
When converting an old jet setup to a submersible is worth it
There's a version of this call where converting is clearly right. The static water level has dropped over the years and the jet can't reliably lift it anymore, so you lose prime every dry August. Or the well got deepened. Or the deep well jet is running constantly, delivering weak pressure and costing real money in electricity while a family of five fights over the shower. In those cases converting solves the problem instead of postponing it, and the pump you put in will outlive the one you took out.
Budget for a full replacement plus the conversion work, on a well that suits it. That's not just a pump. It's new drop pipe and submersible wire down the hole, a pitless adapter cut into the casing if there isn't one, a proper sanitary well cap, a new pressure switch and often a new tank, plus dealing with the old suction pipe and ejector. The old jet pump comes out and the basement gets quiet.
There's also a version where converting isn't possible or isn't smart. A large diameter dug well three feet across with eight feet of standing water isn't a conventional submersible candidate without a sleeve, and the wet plumbing may be in worse shape than the pump. A shallow point well in sand may not have the yield or the casing for it. And if the existing jet setup works, is accessible and is serving a small house fine, spending several thousand dollars to make it quieter is a want, not a repair.
The right way to decide is to measure. Static water level, depth of the well, what the well actually produces, and what the house demands. Call 973-853-1550 if you want those numbers taken before anybody quotes you a pump, because a quote written without them is a guess.