SOMERVILLE, N.J. (AP) _ Hoechst Celanese Corp. has sued units of Eljer Industries Inc. for allegedly selling faulty plumbing equipment and then seeking to evade responsibility in product liability claims.

The suit, filed in Superior Court here, was announced Wednesday by Eljer. Hoechst Celanese spokeswoman Patti Munzer later confirmed it. ''We feel there is due cause, but we really can't comment beyond that,'' she said.

The two companies are defending a number of product liability suits connected with plumbing systems of a hard plastic called polybutylene that turned out to be faulty in some cases.

In defending the suits, the companies are fighting among themselves over liability for the products.

The Hoechst suit names Eljer's former parent, Household Industries, and two wholly-owned subsidiaries, Eljer Manufacturing Inc. and United States Brass Corp.

Hoechst charges the defendants with failing to test their products and fraudulently inducing Hoechst to sell the raw materials to them, Eljer said.

''We deny the allegations against Eljer's subsidiaries and intend to vigorously defend this lawsuit,'' Scott G. Arbuckle, president and chief executive officer of Eljer Industries, said in a statement.