Owner’s manual
How do I find the model number on my 390291658?
Your Craftsman captive air tank model number is typically printed on the tank’s ID label (nameplate) or on a sticker near the pump or pressure switch area. Use that exact model number to match diagrams and parts lists in the 390291658 owner's manual.
Where to look on a captive air tank
Check these common label locations first:
- On the side of the tank near the top shoulder
- Near the pressure switch or gauge manifold
- On the pump mounting bracket or base plate area
- On the back side of the tank (rotate the unit if needed)
- On a paper or foil sticker close to the inlet or outlet fitting
What the model number label looks like
Most Craftsman labels include a few key identifiers. Use the model number exactly as shown (including any dashes).
| Label item | What it’s used for | Example format |
|---|---|---|
| Model number | Matching the correct diagrams and parts | 390291658 |
| Serial number | Identifying production run | Letters and numbers |
| Electrical ratings (if applicable) | Verifying motor requirements | Volts, amps |
Tips if the label is hard to read
If the sticker is worn or painted over, these steps usually help:
- Wipe the label with a damp cloth and mild soap; dry fully
- Use a flashlight at an angle to make faint printing stand out
- Take a close-up photo and zoom in
- Write down every character; one digit off can change the parts list
Why it matters
Craftsman water pump and tank assemblies often share similar-looking components; the correct model number ensures you get the right diagrams, specifications, and compatible replacement parts for your exact setup.
Last updated: March 2026
What are the most common issues with 390291658?
For the Craftsman 390291658 captive air tank (water pump system), the most common problems are loss of water pressure, rapid pump cycling, waterlogging (no usable air cushion), and leaks at fittings or the tank seam. These issues usually trace back to air-charge problems, a failed internal bladder/diaphragm, or plumbing/check-valve leaks.
Common symptoms and what they usually mean
- Pump turns on and off rapidly: tank air charge is low, bladder is damaged, or there is a small system leak.
- Pressure drops quickly when a faucet opens: tank is waterlogged or air charge is incorrect.
- Pump runs but pressure will not build: suction-side leak, clogged inlet, or a failing pump/check valve.
- Water at the tank valve or around fittings: leaking Schrader valve, loose fitting, or tank corrosion.
- Short run time and weak flow: incorrect pressure switch settings or restricted piping.
Quick checks we recommend (safe, high value)
- Shut off power to the pump and relieve water pressure at a faucet.
- Check for visible leaks at threaded fittings, unions, and the pressure switch manifold.
- Verify tank precharge with a tire gauge at the air valve (tank must be at zero water pressure for an accurate reading).
- Listen for air or water at the air valve:
- Air only: normal.
- Water from the air valve: bladder/diaphragm failure.
- Confirm pressure switch cut-in/cut-out behavior and compare to the tank precharge guidance in the owner's manual.
What “normal” looks like (typical targets)
| Item | Typical target for captive air tanks | Why it matters |
|---|---|---|
| Tank precharge | 2 PSI below pressure switch cut-in | Prevents short cycling and waterlogging |
| Cycling frequency | Steady drawdown before pump starts | Protects pump motor and switch contacts |
| Leak condition | No seepage at fittings/valves | Maintains prime and pressure |
Why it matters
A waterlogged or leaking captive air tank forces the pump to short cycle; that overheats the motor, wears the pressure switch, and can lead to premature pump failure. Correct air charge and tight, leak-free plumbing keep pressure stable and extend pump life.
Last updated: March 2026
What is the average lifespan of 390291658?
A Craftsman captive air tank like model 390291658 typically lasts 7 to 10 years in normal residential use. Lifespan depends most on water quality, pump cycling frequency, and whether the tank stays properly pre-charged; the tank bladder and internal corrosion are the usual end-of-life factors.
Typical lifespan and what affects it
- Water quality: high minerals and sediment speed up wear and corrosion.
- Cycling: frequent on-off cycling stresses the bladder and fittings.
- Pre-charge pressure: incorrect air charge causes short cycling and premature failure.
- Moisture and location: damp basements and outdoor exposure increase rust risk.
- Maintenance: periodic pressure checks extend service life.
Quick check: is the tank near end of life?
Use these common symptoms to decide whether to troubleshoot, service, or replace.
| Symptom | Most likely cause | What to do next |
|---|---|---|
| Pump short cycles (rapid on/off) | Low air pre-charge or waterlogged tank | Check pre-charge; follow steps in the owner's manual |
| Pressure swings quickly at faucets | Bladder losing air or failing | Verify pre-charge; inspect for leaks at valve and fittings |
| Water at the air valve (Schrader) | Bladder rupture | Replace the tank (repair is not practical) |
| External rust or seepage | Corrosion or fitting leak | Replace tank or reseal fittings if leak is at a connection |
How we recommend maintaining it
- Turn off power to the pump before servicing.
- Drain system pressure to 0 PSI before checking air charge.
- Check air pre-charge with an accurate tire gauge.
- Set pre-charge to match your pressure switch cut-in (commonly 30/50 or 40/60 systems).
- Recheck for short cycling after restoring power and refilling.
Why it matters
A healthy captive air tank protects the water pump by reducing cycling; that lowers motor heat, extends pump life, and keeps household water pressure steadier.
Last updated: March 2026
