The following lines were added (+) and removed (-):
Disc piston as a design was replaced by a spool type pressure balance valve. In the spool design the spool itself slides towards the supply with the lower pressure. This cuts off the volume of water entering the valve on the high pressure side and allows more water from the low pressure side. Output water temp cannot vary more than 3 degrees. There tends to be much less mechanical motion in this design.Disc piston as a design was replaced by a spool type pressure balance valve. In the spool design the spool itself slides towards the supply with the lower pressure. This cuts off the volume of water entering the valve on the high pressure side and allows more water from the low pressure side. Output water temp cannot vary more than three degrees. There tends to be much less mechanical motion in this design.