Copyright 2018 cloverdale plumbing. Select the right size for your npe. If the problem is only affecting your home, you don't share a drain with another property or there is no other flooding in the area then it is likely to be a problem with your drainage pipes and you should contact a plumber or drainage company if you are in any doubt please contact us on (01624) 687687 for further advice. Homeowners can rely on the combi boiler to provide.