22 mm x 15 mm reducing coupler. Polyfit is a fully demountable and reusable pushfit system for hot and cold plumbing and radiator central heating systems. The radial sealing force provides a more secure watertight seal and the 3-pin protection feature ensures fittings are not accidentally demounted when installing through joists, floors or walls. Pipe stiffeners must be used when using plastic pipe ; these are not required for copper pipe. for first fix installations, pipe and fittings should be tested. The system should be completely filled using water at a maximum of 20°C, and tested at a pressure of 18 bar for at least 15 minutes. for secondary fixings the complete installation, including appliances, should be tested with water to the maximum test pressure allowed by the appliance manufacturers. Polyfit must not be used for gas, oil, compressed air, solar heating, primary or gravity pipework from a solid fuel back boiler.