This type of installation will provide a greater amount of storage in the bathroom so choose a sink/vanity unit that is suited to your requirements. This is a DIY job but you must always be confident in your own abilities before you begin. Consider hiring a professional company such as Mill Hill Plumbers if you are not. You will need to remove any capping from the water lines at some stage. Measure the water and drain line positions on the wall where it is to be fitted. Copy them on to the back of the vanity unit and cut holes as you have marked them. Now cut out the sink hole if it isn’t already. Put the vanity unit over the lines and up against the wall. Ensure it is square and level, then fix in place.Connecting. In line with the maker’s instructions and diagram, connect up the spout, water valves and handles on the basin. Connect the spout to the supply T-piece and hose assembly. Join the water supply hoses to the valves to avoid having to work underneath the sink later. Use plumber’s putty around the drain to help form a seal and seat the fitting in the basins drain. Put a washer with a slip nut on the bottom of the drain fitting and tighten. Screw up the drain stopper coupling with its gasket so it is square with the rear of the sink. Run the stopper’s slip arm through the sink and fix it to the stopper coupling assembly. Fully open the stopper and tighten the arm down. Turn the sink upright and sit it into the cabinet. Glue a threaded adapter coupling onto the drain stub. Fit the trap and screw it to the adapter and sink drain. Make sure the sink water lines are tightened up to their shut-off valves. Now open very slowly the shut-off, and check both lines for leaks. A Mill Hill Plumber can fix leaks. Fill the basin, check the drain for leaks. Drain the water and check the waste joints. This will also put water in the trap to stop sewer gases. Use silicone sealant around the sink rim to seal and finish off the sink installation. “