Provided with a non-return valve to control opening and closing speed. It can be adjusted to optimal opening and closing speed to cater for working conditions when pump starts or stops running. Applicable for high-rises to reduce the production of water hammer and slamming, thus to effect quiet close. Pressure Grade: PN10, PN16, PN25 Diaphram Type: DN50-DN350 Piston Type: DN400-DN800