NORWALK, Conn. (AP) -- Arch Chemicals Inc. said Friday it completed its acquisition of the water treatment chemicals business of Advantis Technologies Inc. from Rockwood Holdings Inc.

Arch purchased the pool and spa chemicals business, including Advantis' manufacturing center and headquarters in Alpharetta, Ga., for about $124 million. The purchase price is subject to a post-closing adjustment based upon final working capital.

The acquisition was financed by borrowings from Arch's revolving credit facility and is expected to add to cash and earnings in the first year.

The businesses generated sales of $71 million in 2007. Arch expects to save about $6 million per year after integrating the businesses.

Shares of Arch Chemicals fell $1.59, or 6.2 percent, to $24.05 in afternoon trading.

Shares of Princeton, N.J.-based Rockwood fell $1.55, or 11.2 percent, to $12.27.