Infinity pools in Portugal: what one costs and how an infinity edge works

How much does an infinity pool cost in Portugal?

Around Lisbon in 2026, an 8 × 4 m reinforced-concrete infinity pool costs roughly €45,000–€75,000 turnkey, and a 10 × 5 m one roughly €70,000–€150,000. Simple projects, with a single edge on a plot with a natural slope, start at around €25,000–€30,000, before rock or heating.

Compared with a conventional pool of the same size, an infinity edge costs at least 20 % more according to a Spanish quotes portal, and about a third more according to a manufacturer operating in Portugal. The difference pays for the overflow wall, the catch gutter, the balance tank, a bigger pump and far more calculation and precision on site.

How does an infinity pool work?

In an infinity pool, the water level sits just above an overflow wall. Water spills in a thin sheet into a hidden catch gutter, drains by gravity to a balance tank, and the pump returns it to the pool through the filter. From inside the pool, the water appears to merge with the horizon.

1. Overflow wall (weir). The top of the wall on the view side sits a few millimetres below the water level and must be perfectly level — one Portuguese builder works to tolerances under 2 mm.
2. Catch gutter. It runs the full length of the infinity edge, below the wall, and collects the water that spills over.
3. Balance tank. Water drains by gravity into this reservoir, which absorbs the water displaced when someone gets in and gives it back when they get out.
4. Pump and filter. The pump draws from the tank, sends the water through the filter and disinfection, and returns it through the return jets, keeping the edge flowing.
5. Automatic top-up. A level sensor in the tank opens the mains supply when evaporation lowers the level, so the pump never runs dry.

How big is the balance tank and what equipment is needed?

The balance tank of an infinity pool should hold at least 10 % of the pool volume: for an 8 × 4 m pool with an average depth of 1.4 m, about 45 m³, that means roughly 4.5 m³. The final sizing, together with the gutter and pump, is done by the pool designer.

Infinity edge or overflow pool? With an infinity edge, water spills over one or more sides into a gutter below, on the view side. With an overflow pool (also called a deck-level or Finnish-gutter pool), water spills all round the perimeter into a grille flush with the paving. Both need a balance tank; only the first creates the horizon effect.

Can an infinity pool be fibreglass, or does it have to be concrete?

Almost all infinity pools are built in reinforced concrete, because the overflow wall must be level to the millimetre and hold back the ground on the drop side. Polyester overflow shells exist, but in Portugal a fibreglass pool with a true infinity edge is rare.

In concrete, the shape and length of the edge are designed around the plot and the view. The trade-off is time: a concrete pool takes 8–12 weeks on site, and an infinity edge, with its tank and walls, usually longer. An 8 × 4 m fibreglass pool without an infinity edge costs €20,000–€32,000 and goes in within days.

What kind of plot does an infinity pool need?

The ideal plot has a natural slope on the view side, so the balance tank sits below the pool with little digging. On flat ground, the pool can be raised with the tank built into the structure. Either way, the reinforced-concrete structure needs a structural design by an engineer.

Does an infinity pool cost more to run?

Yes. An infinity pool uses more electricity, because the pump runs whenever the edge is flowing, and more water, because the falling sheet and the gutter evaporate more than still water. A conventional pool costs €600–€1,600 a year to run; an infinity pool costs more.

• Variable-speed pump. Cuts consumption when the pool is not in use; ask the designer for the expected hourly consumption.
• Scheduled overflow. Ask whether the system lets you switch the infinity effect on only when you are using or looking at the pool.
• Evaporation and wind. On exposed sites such as Cascais and Guincho, top-up water goes up. A pool cover reduces losses, but it does not cover the gutter.
• Heating. A heated infinity pool loses more heat through the moving water; size the heat pump with that loss in mind.
• Cleaning the gutter and tank. Leaves and sand collect in the gutter; our team includes the gutter and balance tank in maintenance.

Do you need a permit to build an infinity pool in Portugal?

Usually not a full licence: an infinity pool attached to a house follows the same rules as any pool and needs a prior notification (comunicação prévia) to the câmara (RJUE, art. 4(4)(j)). In protected areas — the Sintra-Cascais and Arrábida natural parks, REN or RAN land — a licence and outside opinions may be required.

Since 1 October 2026, under Decree-Law 108/2026, works can start once the prior notification is submitted, the fees are paid and the start of works is notified. For an infinity edge, the file usually includes the structural design of the walls and tank. The permits guide explains it all, municipality by municipality.

Is the drop side of an infinity pool safe?

The infinity side is a drop: seen from outside, the wall and gutter form a step that can be high on a slope. A safe infinity pool keeps the drop side out of children's reach, has a guard rail or fence on the lower level, non-slip paving and a wall top that is not used as a walkway.

• Do not use the wall as a walkway. The top is wet and slippery; design access to the pool from the other sides.
• Protect the lower level. If the gutter faces a garden or terrace, fit a guard rail or fence that stops children climbing up.
• Grilles on the suction points. Suction outlets in the tank and the pool should have anti-entrapment grilles.
• Safety cover. An automatic cover protects the pool when it is not in use, but it does not cover the gutter — the fence is still needed.

How does an infinity pool project run?

An infinity pool project with the Pools Portugal Network starts with a survey of the plot and the view, moves through the architectural and structural design and the prior notification, and only then to the build. A concrete infinity pool takes longer than the 8–12 weeks of a conventional concrete pool.

1. 1

   Free study and survey

   1–2 weeks

   Site visit or video call, ground levels, the direction of the view and the wind, machine access and the position of the balance tank.

2. 2

   Architectural and structural design

   2–4 weeks +

   Design of the edge, hydraulic calculation of the overflow, sizing of the tank and pump, and structural design of the walls by an engineer.

3. 3

   Prior notification or licence

   1–3 weeks

   Submission to the câmara, payment of fees and notice of the start of works. In protected areas, outside opinions can take considerably longer.

4. 4

   Construction

   8–12 weeks +

   Excavation, structure, tank, overflow wall, waterproofing, finish and hydraulics. The level of the wall is checked before the finish goes on.

5. 5

   Start-up by our team

   1 week

   Filling, tuning the overflow along the whole edge, balancing the water and a walk-through of the equipment. The same team then looks after maintenance.

If you live abroad, we follow the build with weekly reports — see the guide for foreign owners. For the full construction process, go back to the pool construction guide.