Skimmer or overflow pool? How each system works and which suits your villa
Most people who ask for a pool arrive with a picture: water lying exactly level with the deck, flat as a mirror. That picture is an overflow pool. Then the contractor says "skimmer", and it is not clear whether that is a lesser thing or just a different one. They are two ways of drawing water off the surface of a pool, and each makes its own demands on the site and the plant room. Fox Pools has built both — and infinity edges — in concrete and prefabricated pools since 1993.
Why take water from the surface at all?
Most of what dirties a pool starts on the surface: dust, leaves, sun-cream oils. Draw the water off the surface first and that dirt reaches the filter before it sinks. Skimmer and overflow are two ways of doing it.
How a skimmer system works
- The water sits visibly below the pool edge (in the order of 10 to 15 cm).
- Openings in the pool wall, the skimmers, each have a floating weir and a basket that catches leaves.
- The pump draws water from the skimmers and the floor drain, pushes it through the filter, and returns it through inlets.
- No extra tank is needed: the pool itself holds the water.
In its favour: a simpler system, less civil work around the pool and a smaller plant room. Against it: the visible band of wall above the water, and surface water is taken at fixed points rather than all round — which is why skimmer positions matter relative to the prevailing wind on your site.
How an overflow system works
- The water lies exactly level with the surrounding deck.
- It spills over the pool edge into a channel running round the pool, covered by a grating you walk on.
- From the channel it runs by gravity to a balance tank beside the pool.
- The pump draws from the balance tank to the filter, and the water returns to the pool — usually through floor inlets — raising the level so the cycle continues.
In its favour: the whole surface is skimmed continuously on every side, so the surface stays cleaner, and the look is the familiar hotel look. What it requires: the channel and grating round the pool, a balance tank of calculated size, a larger plant room, and a very accurately levelled edge — water shows up any slope, however slight.
Why a balance tank?
When people get into a pool they displace their own volume of water. In a skimmer pool the level rises slightly and that is the end of it. An overflow pool is already full to the brim, so the displaced water spills into the channel and has to go somewhere that can take it and give it back — that is the balance tank. Its size is calculated at design stage from the pool area and the number of users, never estimated by eye.
And infinity?
An infinity edge is overflow on one side (or more): water spills over a lowered edge into a catch basin below, so the surface seems to run into the horizon. It suits sites with an open view — sea, a slope, a lower garden — and makes no sense if the edge faces a boundary wall. More in our overflow and infinity-edge guide.
The difference in six points
- Water level: below the edge with skimmers; level with the deck with overflow.
- Surface cleaning: skimmers draw from points; overflow skims the whole perimeter.
- Works around the pool: none extra for skimmers; channel, grating and balance tank for overflow.
- Plant room: smaller for skimmer; larger for overflow.
- Space on site: overflow needs room for the tank and extra width for the channel — decisive in small gardens and where the compound's rules require a setback from the boundary.
- Upkeep: skimmer baskets are emptied regularly; with overflow the channel, grating and balance tank are cleaned regularly.
Both give clean water when properly designed and built; the difference is in the look and in what the site has to provide.
When a skimmer pool is the right choice
- A garden with limited area or tight setbacks.
- A family villa pool where simplicity comes first.
- A site with no room for a balance tank or a larger plant room.
When an overflow pool is the right choice
- The deck-level look is a core part of the garden design.
- A heavily used pool — club, hotel or compound.
- A site with room for the channel and tank, and an owner prepared for their regular upkeep.
Three questions to ask any company before you choose
- Where will the balance tank go, and how large is it? If the quotation is for overflow and no tank is mentioned, the quotation is incomplete.
- How many skimmers, where, and why there?
- Is the system stated explicitly in the quotation and on the drawings — skimmer, overflow or infinity? Compare quotations for the same system only.
In short: skimmer is simpler, needs less space and is right for most villa pools; overflow gives water level with the deck and a surface skimmed on every side, in exchange for a channel, a tank and a larger plant room.
Questions people ask
What is the difference between an overflow and a skimmer pool?
In a skimmer pool the water sits below the edge and is drawn through openings in the wall; in an overflow pool the water is level with the deck and spills into a channel round the pool, then to a balance tank before the filter.
Is an overflow pool cleaner than a skimmer pool?
The surface of an overflow pool is skimmed along its whole perimeter, so it looks cleaner, but both systems give clean water when properly designed and built.
What is the balance tank in an overflow pool?
A tank beside the pool that receives the water spilling into the channel — including what bathers displace — and from which the pump draws to the filter.
Can an overflow pool be built in a small garden?
It depends on the space available for the channel and balance tank and on the compound's setbacks; this is settled at the site survey.
What is the difference between overflow and infinity?
An infinity edge is overflow on one or more sides, where water spills over a lowered edge into a catch basin; it suits sites with an open view.
Are both systems available for concrete and prefabricated pools?
Yes, both types are built as skimmer or overflow.
The decision is made on site
The space available, the compound's rules and the way you will use the pool decide it. At the survey our engineer establishes which system suits your ground.