As much as we want to rectify the cause of leakage from its source, sometimes it just may not be feasible or economical. For example, if a swimming pool is causing leakage at a carpark below. Proper method should involve redoing the entire swimming pool by hacking the tiles, laying new waterproofing membrane and reinstalling new tiles. But the scale of work may be just too large and costly comparing to a localised leakage repair with Polyurethane expandable foam injection.
This method, also known as PU Injection or grouting, utilizes mechanical pump to force Polyurethane chemical into voids and cracks that is leaking. The chemical will react with the water and expand, thereby sealing the cracks and stopping water from leaking.