(Recasts and writes through) BARCELONA, Oct 28 (Reuters) - Shares in Spain’s Fluidra , the world’s largest maker of swimming pool equipment, slid on Thursday as nine-month net profit fell short of expectations despite almost tripling from a year earlier. Net profit came in at 221 million euros ($257 million) - a result that CM Capital Markets called below consensus expectations. Fluidra shares were down 5.5% at 34.65 euros in early morning trade. Even so, it is the second best-performing stock in Spain’s Ibex-35 blue chip index this year, having gained 75%. The company also lifted its outlook, the fourth time it has raised guidance this year. With January-September sales having jumped 49% to 1.7 billion euros on residential demand and the North American market, Fluidra now expects annual sales to climb 40%-45% compared with a September estimate of 37%-42%. It maintained an earlier estimate for earnings per share to rise 83%-93%. Noting initial data from October was positive, the Barcelona-based company predicted a “solid” fourth-quarter profit despite global supply chain tensions and a rise in its prices. The company has benefited from pandemic-induced lockdowns that prompted many upper middle-class people to install swimming pools as they were not able to travel during the summer. “The business’s fundamentals remain robust and the positive dynamic continues thanks to the strong demand for new construction (pools), the commercial pool recovery and M&A ... We are prepared for a solid start of 2022,” Fluidra’s Executive Chairman Eloi Planes said in a statement. The company’s net debt has risen 60% from last year to 933 million euros due to acquisitions. In September it announced a $240 million purchase of U.S.-based SR Smith. $1 = 0.8618 euros Reporting by Joan Faus; Additional reporting by Inti Landauro, Tomas Cobos and Joanna Jonczyk-Gwizdala; Editing by Edwina Gibbs