Thank you for using wpj heating, we wish you a great day! Grade d or above gcses, including maths and english would be an advantage. Are you looking for trusted boiler repair and installation services in London? Most residential homes will need boilers with an output range of ,-, btus. Best of luck clearing up your drain and keeping it that way! These are external links and will open in a new window. Ewwwww that smell can you smell that smell?? Our housing service.