Dec. 12 (Bloomberg) — Pennon Group Plc, the third-largest publicly traded water utility in the U.K., is leaving the FTSE 100 in a rebalancing of the index and is being replaced by the leisure travel company Tui Travel Plc.

Pennon, whose shares have fallen 13 percent this year, will become part of the FTSE 250 Index instead following a quarterly review, the FTSE group said in a statement. The changes take effect Dec. 24.

Exeter-based Pennon also owns the waste management company Viridor and South West Water Ltd., a water and sewer service provider for Devon, Cornwall and parts of Dorset. United Utilities Group Plc is Britain’s biggest publicly traded water company.

To contact the reporter on this story: Randall Hackley in London at rhackley@bloomberg.net

To contact the editor responsible for this story: Randall Hackley at rhackley@bloomberg.net