What do washing the dishes and uploading pictures to Facebook have in common?

In most places, not much. But in Paris, they both could help heat your local swimming pool.

To keep its bathers from shivering and its energy bills from ballooning, the city has developed some clever ways to reuse excess heat from two unconventional sources, computer servers and sewage.

The wastewater from sinks, toilets, washing machines and so on pours into the Paris sewer system at an average temperature of 55 to 68 degrees Fahrenheit. At the Aspirant Dunand swimming pool in the 14th Arrondissement of Paris, the stuff runs through pipes underneath the pool, where the warmth is captured with the help of metal plates in the sewage pipes. A heat-pump system then transfers it to the pool water.

The heat source at a swimming pool in the Butte aux Cailles neighborhood of the 13th Arrondissement will have to be kept much drier. A French start-up company called Stimergy is scheduled to install several hundred computer servers in the building’s basement over the next year. The heat thrown off by the servers will go to the boiler that heats water for the pool and locker-room showers — a “data furnace,” if you will.