How does an overflow pool differ from a skimmer pool?
In a skimmer pool water is drawn in through slots in the wall and the level sits 10 to 15 cm below the edge. In an overflow pool the water rises level with the edge and spills over it into a channel, from there to the balance tank and on to filtration. The surface film of dust, pollen and oil leaves with the overflow, so the water is cleaner and calmer, and the view without a visible rim is seamless.
An infinity (vanishing edge) pool is a variant of overflow in which the spill shows on one or more sides: the outer wall reads as a line of glass and the water merges with the horizon. The other sides may be a perimeter overflow or a low rim. It costs more than a skimmer pool because the system is more complex: channels, tank, larger pumps and precise geometry.
Is a balance tank needed?
Yes, without it an overflow pool does not work. The tank (vaso de compensación) receives water that spills over and holds the reserve so the pumps run properly. When bathers get in they displace water and it goes to the tank; when they leave, the pool level drops and the tank returns the water. Without it the pumps would run dry or the pool would overflow uncontrolled.
The designer calculates the volume: water surface area, number of users, water in channels and pipes and wind-driven waves all count. In practice it is a noticeable share of the pool volume. It is usually hidden under the terrace, in the technical area next to the plant room, and needs access for maintenance, ventilation and noise protection. So the space for it and the pumps is planned before the plot is designed, not after.
Where is a sea-view edge possible on a Garraf slope?
On a slope an infinity edge is the most natural: the edge is made on the side where the ground falls away and the retaining wall behind it is hidden from view. The pool sits well on a terrace levelled with retaining walls, so that the spill side faces the sea and service access is from the other.
But a slope means geotechnics: a ground investigation, calculation of retaining walls, drainage and water disposal, because the weight of water saturating the ground affects slope stability. Plots in the Garraf and along the Maresme often carry limits on height, setbacks and nature protection, and if the plot is near the coast the Ley de Costas restrictions are checked. All of this is clarified at the plot selection and design stage, not when pouring concrete.
Can an infinity pool be built on flat ground?
Yes, if you create a level difference: raise the pool on a podium, excavate a lower platform with a catch channel, or sink the overflow channel and hide it behind a wall. A flat plot without a drop in view does not give the "horizon feel", but the spill works as a design element, especially if a wall, a garden or a low area sits behind it.
The solution depends on what you want to see: if it is the sea, the slope decides; if it is simply beautiful water with a clean edge, a raised pool with a channel on the side facing the house or garden is built. Podium height and look are coordinated with neighbours and height rules. On flat ground a plain overflow pool without the infinity effect is often chosen, simpler and cheaper, giving much of the visual effect.
Does an infinity pool evaporate more and how is the noise?
Yes, loss is higher than in an ordinary pool: water runs down the wall, wind carries off spray and the area in contact with air is larger. In heat evaporation from the water surface is several millimetres a day, and in an infinity pool wind losses are added. For an 8 × 4 m pool (32 m2) each millimetre is about 32 litres, so a summer week adds up to a tonne or more. It has to be included in the calculation and in automatic top-up.
Falling-water noise is controlled by the height and profile of the overflow wall and the flow rate: a wide, smooth sheet makes little noise, a narrow stream drums. In a house next to a bedroom, check the noise in advance, put the plant room further away and mount pumps on anti-vibration supports. Edge level precision matters: if it is not level along its whole length to within millimetres, water runs unevenly and looks ragged.
Construction and upkeep: what to plan in advance
An overflow pool is built in reinforced concrete with waterproofing and a finish of mosaic, porcelain or stone. The overflow channel, hidden grille and balance tank add more details than a simple pool, so an experienced crew and a project are needed. There is a separate article on construction timing and stages, explaining what happens from earthworks to commissioning.
Upkeep is more complex than for a skimmer pool: watching the tank level, cleaning channels and grilles, checking pumps. If you do not live in Spain, plan automatic top-up, level sensors and a service contract. The best upkeep is designed in: access, equipment in view and clear instructions for whoever will carry it out.
Where to start and how BCN YARD can help
Start with the plot: slope, views, ground, distance to neighbours and the coast. Then decide whether the infinity effect is needed or a simple overflow is enough, and calculate the tank and plant room. Permits are processed with the house project or a separate pool project.
BCN YARD builds houses and pools in Russian and Spanish, with one person responsible for the site. A plot visit, measurements, an assessment of ideas and a phased estimate where the pool, garden and house run on one schedule.
Frequently asked questions
How much does an infinity pool cost compared with a normal one?
More expensive, because the overflow channel, balance tank, stronger pumps and precise geometry are added. The exact difference is calculated from the project: it depends heavily on slope, finish and size. To get a price you need a plot visit and a technical brief.
Does an infinity pool need a permit?
Yes, like any pool: a project and a licence are needed, and on a slope also a geotechnical calculation of retaining walls. Additional limits arise near the coast and in protected areas. There is a separate article on pool permits explaining the process.
Can an infinity pool use salt water?
Yes, but salt affects stone, metals and electronics, which must be considered in choosing finishes. The surrounding stone and the channel are sealed, and metal parts are 316 stainless or titanium. More on water treatment in the article on salt, chlorine and UV.