A dim-witted cop who forced the evacuation of a police station after pouring five litres of petrol down a drain has been told off by Scottish Water.The smell of fuel was so strong that officers had to leave the station in Bellshill, Lanarkshire, and wait for Scottish Water and the Fire Service to give them the all-clear to go back in.Scottish Water said: “This incident is a reminder to all customers to ensure they put only the correct things down toilets, sinks and drains."Only the three Ps, pee, poo and toilet paper, should be flushed down toilets.”Earlier, a source said: “Police seized five litres of fuel following a wilful fire raising incident.“Instead of disposing of it properly, an officer poured it down the drain in the men’s