Best of luck clearing up your drain and keeping it that way! Follow your combi boiler user's manual and turn the system back on, then allow the heating to run as usual. From sinks and toilets to sump pumps and frozen pipes, there's no household plumbing job beyond our expertise! Sanitary plumbers who are registered with sps, and hold, minimally, a builder certificate or other relevant qualifications acceptable to pub. Do they offer an after sales service? From a.