UPDATE 1-Valero Houston refinery unit suffers upset

(Adds Valero comment, paragraph 2)

HOUSTON, March 21 (Reuters) - Valero Energy Corp's (VLO.N: Quote, Profile, Research) 130,000-barrel-per-day (bpd) Houston refinery sustained an upset in an ultra low sulfur diesel facility on Thursday, according to a notice filed with state pollution regulators on Friday.

The upset "should not result in a material impact on production," Valero spokesman Bill Day said in a statement.

The complex 5 ULSD facility upset "was attributed to substantial feed pressure variations and subsequent upset of make-up and recycle compressor systems," according to the notice filed with the Texas Commission on Environmental Quality.

(Reporting by Erwin Seba, editing by Richard Chang)