The 2" Watts Series 709 Double Check Valve Assembly was in production from 1973-1993. It is a bronze bodied, two cover, wye pattern device. The 709 uses a plastic "cage" type seat and a brass check poppet. The plastic cage locks into the cover with a quarter turn. A hot water version was made and designated with a "HW" after the model number. The hot water version uses a stainless steel seat. No special tools are required for servicing