Water in Monaco: Where It Comes From, What It Costs

A principality that buys most of its water

Monaco covers barely two square kilometres and has no river of its own, yet it supplies around 10,000 subscribers with drinking water year-round. It manages this through a mix of local springs and long-standing purchase agreements with France — a balance that has been in place, in one form or another, since 1930.

The whole chain, from the spring to the outfall in the sea, is run by a single company: the Société Monégasque des Eaux, known as SMEaux. It is the concessionaire of the public drinking-water service and also operates the Principality's wastewater treatment plant. Around 40 staff keep both services running 24 hours a day, 365 days a year.

Where the water comes from

Seven local sources

Monaco draws on seven springs and wells inside or just above its territory: Ingram, Testimonio, Marie, Vaulabelle, Puits Nord, Puits Annonciade and Fontdivine. Together they cover between 20% and 50% of annual consumption — the share swings with rainfall, which is why the local resource alone has never been enough.

Water bought from France

The balance is purchased from French suppliers under conventions signed with the relevant authorities across the border. It arrives from three directions:

• the canal de la Vésubie, the historic supply, secured by a convention signed in 1930
• wells in the plaine du Var
• the Roya, added in 1981 as a second external feed

Between them they bring 2 to 3 million cubic metres of drinking water a year into Monaco's reservoirs. In May 2015 SMEaux renewed the arrangement through a three-party convention with the town of Menton and the SIECL, committing to maintain delivered volumes and to help finance repairs and modernisation of the shared network.

Treatment, storage and distribution

All the local sources feed a treatment plant tucked beneath SMEaux's customer offices on avenue Princesse Grace, at Larvotto. The process is deliberately simple: sand filtration to strip out impurities, then disinfection with chlorine dioxide to guarantee bacteriological safety. Treated water is then pumped up to storage at a maximum rate of 500 m³ an hour.

The rest of the system:

• 25,000 m³ of storage spread across seven reservoirs, so the network keeps pressure and buffer capacity
• 110 km of distribution mains, in diameters from 500 mm down to 40 mm
• a further 20 km of service connections serving roughly 10,000 subscribers
• a network efficiency rate held above 95% — very little of what enters the pipes is lost to leaks

Quality control

Monaco's water is checked from three independent directions: SMEaux's own monitoring, an outside laboratory, and government oversight. That adds up to roughly 5,500 analyses a year across around 60 parameters. Tap water is safe to drink everywhere in the Principality, and SMEaux publishes a live "météo de l'eau" indicator on its website showing how comfortable the resource situation currently is.

What you pay

The price of a cubic metre — 1,000 litres — is €4.28 including tax from 1 July to 31 December 2026. It is reviewed twice a year, so check smeaux.mc before relying on it for a budget.

That single figure covers more than it looks:

• the supply of drinking water to your tap, and
• the treatment of that same water after use, before it is discharged into the sea

On top of the per-cubic-metre price sits a subscription charge, calculated from the diameter of your connection and of your meter — so a large villa or a commercial premises pays more than a studio.

In practice, most people moving into a rented apartment in Monaco never open a water account at all: the supply is already active and the cost arrives through the building's service charges. See setting up utilities in Monaco for how this fits alongside SMEG and Monaco Telecom.

Where the wastewater goes

Used water does not simply run into the Mediterranean. It goes to the UTER — the Usine de Traitement des Eaux Résiduaires — built into ten underground levels of the "Le Triton" building in Fontvieille, and operated by SMEaux.

The plant serves more than Monaco. Its catchment takes in the whole of Beausoleil, about 90% of Cap-d'Ail and roughly 50% of La Turbie, giving it a treatment capacity of 130,000 population equivalent — a figure raised by more than 30% from the previous 100,000 when the plant was extended. In dry weather it handles about 31,000 m³ a day, with a peak capacity of 1,800 m³ an hour.

Treatment combines physico-chemical settling, biological treatment on moving bed carriers and lamellar clarification, with screening fine enough to remove particles above 10 microns. More than 95% of the pollution load is removed. The treated effluent leaves through an outfall 800 metres offshore at a depth of 100 metres.

Because the plant sits underneath a dense residential and business district, odour control is a design constraint rather than an afterthought: all the air extracted from the water-treatment halls (34,000 m³/h) and the sludge halls (24,000 m³/h) is scrubbed before release. The sludge itself goes next door — around 4,400 tonnes a year are burned at the waste-to-energy plant run by the Société Monégasque d'Assainissement, Monaco's waste operator.

A short history

• 1930 — local springs no longer cover demand; Monaco signs a convention with the Compagnie Générale des Eaux to bring in water from the Vésubie
• 1940 — the government decides to unify the several networks then in service
• 1942 — the Société Monégasque des Eaux is created as concessionaire, followed by a rebuilding programme that includes the 6,000 m³ Exotique reservoir
• 1981 — the Roya is brought in as a second external supply
• 2015 — the supply convention is renewed with Menton and the SIECL

Practical contacts

Société Monégasque des Eaux (SMEaux) 29 avenue Princesse Grace, 98000 Monaco — opposite the Larvotto beaches Customer service: +377 93 30 83 67, Monday to Friday 8:15–16:45 without a lunch break 24-hour emergency line: +377 93 30 39 36 smeaux.mc

Related reading

• Utilities in Monaco: electricity, gas and water — who supplies what
• Setting up utilities — the practical steps when you move in
• Waste and recycling in Monaco — the SMA side of the picture
• Monaco's environmental policy