Common Water Pump Problems and How to Fix Them Yourself

Quickly identify malfunctions

1. The pump does not start

Usually, it's due to the power supply or the switching, not the pump itself.

Solution: Try a different outlet and check if the residual current device hasn't tripped. Inspect the entire length of the cable: a damaged or kinked cable is the number one cause of pump malfunctions. If your pump uses a float switch, lift it manually. If the pump starts now, the float switch was jammed or is defective — read everything about mechanical float switches.

Float switch broken? A separate electronic RP CRAB float switch (€99.50) fits any submersible pump with a 230V plug and cannot get stuck. Also view all separate float switches.

Does the fuse blow immediately again or do you smell burning? Then stop: the motor is likely damaged. View replacement pumps.

2. The pump loses suction power

If the pump pumps less powerfully than before, there is almost always something in the way.

Solution: Remove the pump from the water, clean the suction strainer and impeller (unplug it!). Check the discharge hose for kinks and blockages. For a pump with a suction line: check that all connections are airtight — rub a soapy solution along them; where bubbles form, air is leaking in. Is the head higher than the pump can handle? Then see how to read a pump curve.

3. The pump makes an unusual noise

Rattling, screeching, or grinding indicates dry running, cavitation, a stone in the impeller, or worn bearings.

Solution: Cavitation occurs when the pump draws in air instead of water, for example due to a too low water level. Place the pump deeper or let a float switch turn it off in time — a pump without a float switch that runs dry quickly overheats (with or without a float switch?). Remove dirt from the impeller. If the bearings continue to make noise, replacement is usually more economical than overhaul.

4. The pump runs, but no water comes out

The motor runs, but nothing comes out of the hose. Causes: a stuck check valve, a clogged suction strainer, or an airlock in the pump.

Solution: Check that the check valve is not jammed or installed incorrectly. Clean the suction strainer and impeller. Airlock? Hold the pump diagonally under water for a moment so the air can escape. For a surface pump: fill the pump housing and suction line with water through the fill opening and carefully bleed it.

5. The pump constantly switches on and off

Switching on and off in rapid succession (cycling) quickly wears out the motor and the switch.

Solution: For a submersible pump, this often happens because water from the discharge line flows back into the pit: install a check valve. If the pit is small, adjust the float switch so that the difference between switching on and off becomes larger. For a pressure booster or domestic water system, a leaking pressure vessel membrane or a wrongly adjusted pressure switch is the usual cause.

Tip: the Pentair Simer 6 has a built-in check valve, so the discharge line does not drain.

6. Leakage around the pump

Leaks are almost always caused by loose couplings, worn seals, or a damaged hose.

Solution: Tighten hose clamps, replace worn rubbers and porous hoses. If water or oil leaks from the pump housing itself, the shaft seal is broken: water can then reach the motor. For most pumps, this is no longer a sensible repair.

Repair or replace?

Replacement is usually smarter if:

• the motor no longer starts while power, cable, and float switch are in order;
• water or oil leaks from the motor housing;
• the pump is older than 8–10 years or repair costs more than half the price of a new pump;
• you still have water while the pump is idle — then you don't want to wait for a repair.

For the most common situations (basement, crawl space, well, or flooding), our pump experts recommend these pumps:

MOST POPULAR

Pentair Simer 6

Flat suction up to 2 mm, built-in check valve, plug & play.

€269,50

View pump

AUTOMATIC

Simer 6 + CRAB float switch

Switches on and off automatically, even at very low water levels. For sumps or crawl spaces.

€339,80

View pump set

SUMP / BASEMENT WITH FLOAT SWITCH

Pentair Jung U3K(S)

Drainage pump for clean to lightly contaminated water. With float switch and 10 m cable.

€425,49

View pump

Need a dirty water, sewage, or lifting station pump? View all submersible pumps or wastewater pumps.

Preventive maintenance prevents most problems

• Clean the suction strainer and impeller quarterly, and immediately after use in muddy water.
• Test a pump with a float switch twice a year by lifting the float.
• Check the cable and hoses for cracks and kinks.
• Drain the pump and pipes in winter if not in use.
• Important basement or sump? A high water alarm warns you before disaster strikes.

Frequently asked questions

Why doesn't my submersible pump start?

Usually due to a stuck or defective float switch, a tripped residual current device, or a damaged cable. Lift the float switch manually: if the pump starts then, it's due to the float switch.

How long does a submersible pump last?

A good submersible pump typically lasts 8 to 15 years with normal use. Dry running, sand, and dirt significantly shorten its lifespan.

Can a submersible pump run dry?

Most cannot: they are cooled by the water they pump. Use a pump with a float switch or sensor so it switches off automatically.

How much does a new submersible pump cost?

A reliable submersible pump for a basement or crawl space costs approximately €250 to €450. Pumps for dirty water or sewage are more expensive.