What Is an Above Ground Pool Skimmer? | The Wall-Mounted Filter Inlet

An above ground pool skimmer is a wall-mounted device that pulls surface water into the filtration system, trapping debris before it sinks.

Your above ground pool skimmer is the rectangular opening built into the pool wall that constantly draws the top layer of water into the filter. It’s the reason leaves, bugs, and sunscreen film disappear from the surface instead of sinking to the floor where they’d be far harder to clean. The skimmer housing connects to the pump via a hose, and the whole assembly works together to keep the water circulating and clear.

Understanding how this part works, what it’s made of, and how to install it matters for anyone setting up a new pool or replacing a cracked unit. The parts below break down everything you need to know.

What Parts Make Up an Above Ground Pool Skimmer?

A skimmer isn’t one piece — it’s an assembly of several components that work together. Most units share the same basic anatomy:

• Skimmer body — the main housing that mounts through the pool wall.
• Face plate — the visible front piece that holds the assembly against the wall.
• Wall gasket(s) — rubber seals that prevent leaks between the skimmer, the pool wall, and the liner.
• Screws — fasteners that pull the assembly tight against the wall.
• Basket — a removable strainer that catches leaves and large debris.
• Weir door — a floating flap that lets water in but keeps debris from floating back out.

Some models include additional parts, but this is the standard set you’ll find in most above ground pool kits.

How Do You Install an Above Ground Pool Skimmer?

Skimmer installation follows a predictable sequence, whether you’re working with a factory pre-cut hole or cutting your own. The official round-pool installation manual from Swimline’s Impress line lists the same basic order: position the gaskets, align the face plate, fasten screws evenly, then cut the liner only after the skimmer is fully secured.

More specifically, the steps run like this:

1. Place the wall gasket(s) around the skimmer cutout on the outside of the pool wall, aligning the gasket layers properly.
2. Position the skimmer body into the cutout from the outside, and the face plate on the inside.
3. Insert the screws and tighten them evenly in a crisscross pattern — never with a power drill for final tightening.
4. Only after the skimmer is fully secured, cut the liner out from inside the skimmer opening.
5. Bring the water level up to the middle of the skimmer opening before starting the filter.

The reason for the “no power drill” warning is simple: cross-threading the screws can strip the threads, causing leaks and corrosion that ruin the seal. Hand-tighten everything evenly to avoid this.

How Do You Winterize a Skimmer Without Damaging It?

Winterizing a skimmer comes down to keeping water out of it and leaving the assembly intact. The Swimline Discovery round-pool manual offers specific guidance on what to do and what not to do.

• Do not plug the skimmer drain hole. It needs to stay open so water can escape, not freeze and crack the housing.
• Remove hoses attached to the skimmer and return fittings.
• Do not let water freeze in the skimmer. If it does, expanding ice can crack the plastic.
• Leave the skimmer attached to the wall. Taking it apart invites liner damage and lost parts.
• Keep the skimmer lid installed. It keeps snow, ice, and debris out of the opening.

Following these steps each fall prevents the most common cause of cracked skimmers: trapped water freezing and expanding.

What Are Common Skimmer Mistakes to Avoid?

Most skimmer problems come from a handful of installation and maintenance errors. The sources consistently flag these:

• Cutting the liner too early. The liner must be cut only after the skimmer is fully secured, or the liner can shift and misalign.
• Overtightening or cross-threading screws. This is the leading cause of leaks around the face plate.
• Misaligning gasket layers, face plate, or liner cutout. A single misaligned layer breaks the seal, and water finds the gap.
• Plugging the skimmer drain hole. This traps water that later freezes and cracks the housing.
• Letting water freeze in the skimmer. Ice expansion is the #1 killer of skimmer bodies.

One note on installation guides: not all skimmers are identical. The sources note that dimensions, hose sizes, and included parts vary by manufacturer and model, so always match your replacement parts to your specific unit rather than assuming universal fit. If your pool has a vinyl liner, pay extra attention to gasket placement around the liner/wall/skimmer assembly — the liner is the thinnest layer and the easiest to damage during installation.

If you’re shopping for a replacement or a new installation, our tested roundup of the best above ground pool skimmers compares the top models on fit, build quality, and ease of installation.

When everything is installed correctly — gaskets sealed, screws hand-tightened evenly, liner cut clean — the skimmer does its quiet job: pulling surface water through the basket, trapping debris, and sending clean water back to the pump. That’s the whole system, working the way it should.