Are you making a costly laundry mistake when it comes to the weekly wash? One-third of people have absolutely no idea how much detergent to put into the washing machine when washing clothes... and it could be about to cost them a pretty penny. A new survey of 2,000 householders reveals that 35 per cent completely ignore the guidelines printed on their detergent brand. According to the survey, conducted by GlotechRepairs.co.uk, 40 per cent of people also overfill their washing machine drum, which is never supposed to be more than three-quarters full, and compound the mistake by adding even more detergent to the drawer. Using too much detergent can cause a blockage in the machine, something that costs an average €144 to fix. Plus, an overfilled washing machine causes clothes to spin around in one large mass, meaning washing machine detergent won't dissolve enough to clean your clothes properly. It could even prove dangerous; undissolved detergents on clothes can remain on clothing and irritate skin, particularly in babies and small children. Nearly half of people surveyed wash between one and three loads a week, but 14 per cent admitted their machine is running daily, seven times a week. Unsurprisingly, women were 16 per cent more likely to use their washing machine six times a week, while men were more likely to do laundry three times a week.