Rheem Manufacturing agreed to buy Raypak.

The two privately held water-heater companies reached a final agreement for Rheem to buy Westlake Village-based Raypak for an undisclosed sum pending approval from federal antitrust regulators. Raypak, with 300 employees, has annual revenue of $24.6 million, according to Standard & Poor’s. It put New York-based Rheem’s revenue at $800 million to $900 million.