Pulsation, low water volume, a chattering or vibrating hose, and fluctuating pressure are classic signs that something inside the pump head is worn — packings, seals, check valves, or related components.
Jumping straight to a full rebuild is expensive and often unnecessary. Follow this diagnostic order so you fix the actual problem instead of guessing.
1. Start at the water inlet (tank to pump)
Before you touch the pump, confirm the supply side is solid:
- Hoses in good condition (no soft spots, cracks, or collapses)
- Hose clamps tight
- Strainers and filters screwed down properly and not cracked
- No air bubbles in the suction line
Air or restricted flow here will mimic pump problems every time.
2. Check the unloader
Once the inlet is confirmed clean:
- Watch the unloader — it should move smoothly up and down when you squeeze and release the trigger
- Put a gauge on it and watch the pressure
If the pressure is surging up and down, the cheapest and easiest next step is to swap the unloader with a known good one. A failing unloader causes a surprising number of these symptoms.
3. Inspect the check valves
If the unloader is good, move to the check valves in the pump head. These allow water into the pump but prevent it from flowing backward.
Remove them and test:
- Blow air through the stainless lip side — you should be able to blow but not suck
- Check that the plastic isn’t cracked
- Inspect the O-ring in the cylinder — it should not be cut, flattened, or rough
If they pass these checks, the check valves are usually fine.
4. Packings and seals
Only after the first three steps point here should you go after the packings and seals. This repair requires specialized tools. Damage the brass components while trying to do it without the right equipment and the bill climbs fast.
How packings and seals get damaged: Running the pump low on water (or dry) repeatedly is one of the fastest ways to kill them. The longer the pump runs without a solid water supply before you shut it down, the more damage you do.
We offer this repair in-house
If you need packings replaced, check valves swapped, or a full pump head service, we handle it for contractors. Reach out and we’ll take care of it properly the first time.
Following this order keeps you from replacing parts that aren’t the problem and protects the expensive components inside the pump.