It has been suggested that grinding lines that get deeper towards the edge of the cill will allow the water to escape instead of pooling. Its sounds a good idea and we have tried endless other ideas including every water proofer on the market. Looking at this cill it does not have the slight slope required for the water to fall away. Due to the force of the wind - we are exposed on the top of the Pennines - the water pools and eventually forces its way through. New windows fitted last year and the same problem still exists. Interested to know if anyone has ever tried this idea?