Owner’s manual
What are the symptoms of a failing water pump?
On the Craftsman well jet pump model 390251883, a failing pump typically shows up as no water delivery, low pressure/low flow, frequent cycling, air spurting at faucets, or a motor that will not run or overheats. These symptoms usually trace back to loss of prime, air leaks, a clogged jet/impeller, or pressure switch issues (see the owner's manual).
Common symptoms you can see at the house
- Pump runs but no water is delivered (often a priming or suction-side issue).
- Pump delivers water but won’t reach full capacity (restricted piping, low well level, or jet/impeller restriction).
- Pump won’t shut off (pressure switch out of adjustment, clogged jet/impeller, or water demand/leak).
- Pump cycles too frequently (waterlogged tank, leaks, open valves, or pressure switch setting).
- Air spurts from faucets (picking up prime, suction leak, gaseous well, or intermittent over-pumping).
What usually causes those symptoms (and what to check first)
Start with the easiest, highest-impact checks:
- Prime and suction integrity: confirm proper priming and check suction-line fittings for air leaks.
- Jet/impeller restriction: debris can clog the jet or impeller and reduce flow.
- Foot valve/check valve: a leaking foot valve can cause loss of prime and repeated re-priming.
- Pressure tank air charge: this model family calls for 40 PSI air charge for proper operation; incorrect charge can cause short cycling.
- Pressure switch condition: dirty or “frozen” contacts can prevent proper on/off control.
Quick symptom-to-likely-cause guide
| Symptom | Most likely causes | First action |
|---|---|---|
| Motor runs, no water | Improper priming, air leak, leaking foot valve, clogged jet/impeller | Re-prime; inspect suction line; clean jet/impeller |
| Won’t shut off | Pressure switch out of adjustment, clogged jet/impeller, faucets left open | Check demand/leaks; inspect switch; clear restriction |
| Cycles too often | Waterlogged tank, leaks, low air charge, pressure switch setting | Check tank charge; look for leaks; verify switch setting |
| Motor won’t run | Disconnect off, blown fuse, defective starting switch, loose wiring, dirty pressure switch contacts | Verify power; inspect wiring; clean contacts |
Why it matters
These symptoms are more than an inconvenience; frequent cycling and running without proper prime can overheat the motor and accelerate wear on internal components like the jet/impeller and seals.
Last updated: February 2026
How many labor hours does it take to replace a water pump?
Replacing the water pump on a Craftsman shallow well jet pump model 390251883 typically takes 1 to 3 labor hours for an experienced technician when the piping and wiring disconnect cleanly. Plan extra time if fittings are corroded or the system needs priming and pressure adjustments afterward; use the owner's manual service steps.
Typical labor time breakdown
These are common time ranges for a well jet pump replacement (not an automotive water pump):
- Shut off power, open a faucet to relieve pressure, drain the pump: 15 to 30 minutes
- Disconnect wiring and piping: 30 to 60 minutes
- Swap the pump and reseal threaded joints: 30 to 60 minutes
- Prime, restart, check for leaks, verify pressure operation: 15 to 45 minutes
What can make the job take longer
These issues add labor time on a 390251883 installation:
- Rusted or seized unions and fittings that require cutting or rethreading
- Rework to correct discharge piping safety (pressure relief valve setup)
- Electrical corrections (wrong voltage wiring, blown fuse, damaged conductors)
- Pressure tank or suction-side air leaks that prevent the pump from building pressure
- Extra troubleshooting after startup (short cycling, no prime, low pressure)
Quick planning table
| Situation | Typical labor hours |
|---|---|
| Easy access, good unions, minimal replumbing | 1.0 to 2.0 |
| Average replacement with priming and minor replumbing | 2.0 to 3.0 |
| Rusted piping, wiring repairs, or system troubleshooting | 3.0 to 5.0 |
Why it matters
This pump operates under hazardous pressure and the motor runs hot during normal operation. Building in time for safe shutdown, draining, priming, and leak checks prevents repeat service calls and protects the pump and piping.
Last updated: February 2026
What is the most common problem of a water pump?
For the Craftsman well jet pump model 390251883, the most common problem is loss of prime (air entering the suction side). When that happens, the motor can run but the pump delivers little or no water, or it short cycles. Use the owner's manual troubleshooting chart to narrow the cause.
Most common symptoms
- Motor runs but no water is delivered
- Low water flow or the pump will not reach full capacity
- Air spurts from faucets while the pump is trying to pick up prime
- Pump cycles too frequently (short cycling)
- Pump runs but does not shut off
Common causes (what we check first)
- Air leaks on the suction line: loose fittings, unions, clamps, or cracked piping
- Leaking foot valve/check valve: water drains back and the pump loses prime between cycles
- Improper priming after service: prime the pump exactly as described in the manual
- Clogged jet or impeller: debris or mineral buildup restricts flow and pressure
- Frozen pipes: thaw and protect piping below the frost line
Quick troubleshooting map
| What you observe | Most likely cause | Best next step |
|---|---|---|
| Motor runs, no water | Not primed, suction air leak, foot valve leak | Re-prime; check suction fittings and foot valve |
| Cycles too frequently | Waterlogged tank, plumbing leak, pressure switch setting | Check tank air charge; inspect for leaks |
| Won’t shut off | Pressure switch out of adjustment, clogged jet/impeller | Inspect/clean jet or impeller; verify switch operation |
| Motor won’t run | Fuse, wiring, starting/pressure switch issue | Check power supply, wiring connections, switch contacts |
Why it matters
A jet pump that runs without prime or short cycles overheats the motor, wears internal components faster, and causes unstable household water pressure. Fixing suction leaks and valve problems early prevents repeat priming issues.
Last updated: February 2026
Is a 0.5 hp water pump enough for a home?
A 0.5 HP pump is enough for light household demand in some shallow-well setups, but many homes need more capacity to keep steady pressure and flow when multiple fixtures run. For Craftsman model 390251883, use the pump performance table in the owner's manual to match GPM at your pumping depth.
What matters more than horsepower
We size a well jet pump by the flow you need (GPM) at the pressure you want (PSI) and the total head the pump must overcome (lift plus friction losses).
Check these items:
- How many fixtures run at once (shower, washer, irrigation)
- Pumping water level (distance from water level to pump), not just total well depth
- Suction lift limits for shallow-well jet pumps (commonly up to about 20 ft)
- Horizontal run length and pipe size (small pipe increases friction loss)
- Pressure tank size and pressure switch cut-in and cut-out settings
Model 390251883 performance reference (from the manual)
The manual lists model 390251883 flow at 40 PSI discharge pressure at different pumping depths.
| Pumping depth | Flow (GPM) at 40 PSI |
|---|---|
| 5 ft | 10.9 |
| 10 ft | 10.4 |
| 15 ft | 8.6 |
| 20 ft | 7.5 |
Why it matters
If the pump cannot meet demand at your depth and pressure, you get pressure drop, weak shower flow, and long run times. If the system is restricted (air leaks, clogged jet/impeller, undersized piping), performance drops even with adequate horsepower.
Quick signs the pump is too small (or the system is restricted)
- Pressure drops sharply when a second fixture opens
- Pump runs but struggles to reach shut-off pressure
- Frequent cycling (short run times)
- Slow recovery after heavy water use
Last updated: February 2026
