Skimmer vs Overflow Pools: What Is the Difference?

How skimmer and overflow pools work: surface cleaning, appearance, the balance tank, construction complexity and day-to-day operation.

One of the most important technical decisions in a pool design is how water is drawn from the shell and sent to the filter. It is not just about equipment: it determines how the pool edge looks, the water level, the required construction accuracy and even the size of the plant room. The two main systems are skimmer pools and overflow pools.

Why the water surface matters

Most of the dirt in a pool collects on the surface: leaves, dust, insects and a film from sunscreen and body oils. If this is removed before it sinks, water clarity improves considerably and the demand for disinfectant falls. The main job of both systems is to collect surface water, but they do it in different ways.

How a skimmer pool works

A skimmer is a box built into the top of the pool wall. Its mouth has a floating weir, and when the pump runs, surface water is drawn in through it. A basket inside catches leaves and larger debris, and the water travels by pipe to the filter. Clean water returns to the shell through wall inlets.

In a skimmer pool, the water level is kept a little below the pool edge so it sits in the middle of the skimmer mouth. That leaves a visible waterline beneath the coping. The system is relatively simple, less demanding on construction accuracy and is used in most private pools.

It has weaknesses. Skimmers only draw from the area around them, so if the wind pushes debris into a corner without a skimmer, it stays there. The number and position of skimmers are chosen according to pool size and the prevailing wind. When many people are swimming, the water level fluctuates and skimmers work less effectively. When the level changes through evaporation or rain, the skimmer mouth either starts drawing air or ends up submerged, so the level needs regular monitoring, and sometimes an automatic top-up valve is installed.

How an overflow pool works

In an overflow pool the water level is flush with the edge. Water spills over the entire perimeter, or several sides, into a grated channel and flows from there to a separate balance tank. The pump draws water from the tank, passes it through the filter and returns it through floor or wall inlets.

The water surface sits level with the coping, creating a mirror effect. Surface debris is removed evenly along the whole perimeter, so water clarity is usually more stable. Waves created by swimmers flow into the channel rather than bouncing back, which is an advantage in pools used for exercise.

The balance tank and technical issues

The key extra component of an overflow system is the balance tank. When swimmers enter the pool they displace water, which flows into the tank; when they leave, water is drawn back. Tank volume is calculated from pool size and the number of people swimming at once. The tank needs space, which means a larger plant room or underground volume.

The edge of an overflow pool must be precisely level. A small difference shows immediately as water flowing over one side but not the other. This demands high accuracy in the concrete, finishes and channel work. The overflow channel and grating also need regular cleaning.

Water spilling into the channel makes a gentle running sound. Some enjoy it as background; near bedroom windows it should be considered. Outdoors, an overflow surface can slightly increase evaporation and cooling.

Quick comparison and choice

• Appearance: a visible waterline in skimmer pools, a mirror surface flush with the edge in overflow pools.
• Surface cleaning: along the whole perimeter in overflow pools, at fixed points with skimmers.
• Construction: skimmer pools are simpler; overflow pools require precise work and a balance tank.
• Space: an overflow system needs additional volume for the balance tank.
• Upgrading an existing pool: converting from skimmer to overflow means major structural changes.

For a small garden pool with simple operation, a skimmer system is often enough. If architectural impact, more stable water clarity and heavy use matter, an overflow system is worth considering.

Within its architectural design and construction services, Zaferoğlu İnşaat develops garden solutions together with the architecture of the house. If an overflow pool appeals, check with us first whether the site plan has room for a balance tank.