Why Are My Drains Blocked? Blockages can be caused by a build up of fats, oils, grease or soaps, dirt, silt, leaves or foreign objects, or structural defects like roots, corrosion or subsidence. And whatever the cause, the consequences can be serious: bad smells, a collapsed sewer pipe or a toilet overflowing. The solution may involve removing an obstruction, drain cleaning or even repairing a structural defect. The Tools We Use Whatever the problem, Plumbingforce have all the tools we need to do the job. A problem caused by build up of hard scale, fat or grease can be broken down in seconds by high-pressure water jetting.