Pool skimmers are built into the pool wall at the water surface. They continuously draw water from the surface where leaves, insects, sunscreen residue, and other debris collect before they can sink and decompose in the pool.
Key Facts
- Skimmer efficiency depends on correct water level: mid-skimmer opening, typically halfway up the face plate.
- A clogged skimmer basket reduces pump suction and can cause cavitation damage to the pump.
- Check and empty the skimmer basket every 2–3 days or after any significant debris event.
- A weir door (the flap inside the skimmer) prevents debris from returning to the pool when the pump stops.
How Skimmers Work
Pool skimmers are built into the pool wall with an opening at the water surface. The pump draws water through the skimmer inlet, pulling surface water (and the debris floating on it) into the skimmer housing. A weir door at the skimmer opening creates a small waterfall effect that increases the velocity of surface water entering the skimmer, improving debris capture. Inside the housing, a basket catches debris before the water continues to the pump and filter. The captured debris is removed when you empty the basket. Skimmers work best when the pump is running — during pump-off periods, the weir door closes and prevents debris from floating back out.
Correct Water Level
Water level is critical for skimmer performance. The pool water surface should be at the midpoint of the skimmer opening — approximately halfway up the skimmer face plate. If the water level is too low, the skimmer draws air instead of water, starving the pump and potentially causing cavitation damage. If the water level is too high, surface water flows over the pool edge rather than through the skimmer, and the skimmer captures debris poorly. During summer when evaporation is high, check the water level weekly and add water as needed to maintain the correct level.
Skimmer Maintenance
Empty the skimmer basket every 2–3 days or whenever it is more than half full. A full basket reduces pump suction and increases pump wear. After a wind event or storm, empty the basket immediately — wet leaves compact quickly into a solid plug that can block pump suction entirely. Inspect the basket for cracks or holes periodically — a cracked basket allows debris to pass into the pump. Annually, inspect the skimmer housing for cracks and the weir door for proper function. In areas with freezing winters, the skimmer body is a common freeze-damage point — ensure the water level drops below the skimmer intake when winterising.
Examples
A pool owner notices that leaves are collecting in the pool bottom instead of being caught by the skimmer. Inspection shows: the water level is 4 inches below the skimmer opening — too low for effective skimming. The pump is drawing air at the skimmer, causing it to gurgle intermittently. Topping up the pool water to mid-skimmer level immediately improves surface flow. Within 24 hours, the skimmer is capturing debris efficiently and the pump runs silently.
Common Mistakes to Avoid
- Allowing the water level to drop below the skimmer opening during summer evaporation — this causes the pump to pull air and can damage it.
- Not emptying the skimmer basket before a storm, which can fill it to capacity and block all suction within hours.
- Placing chemical tablets directly in the skimmer basket — the concentrated acid from dissolving tablets passes directly through the pump and can damage pump seals and heat exchanger components.
- Pool & Hot Tub Alliance — Pool & Spa Operator Handbook, 2022