Blocked Drains in Cardiff

Most of the blocked drain calls we take in Cardiff are on Victorian and Edwardian terraces — Roath, Cathays, Canton, Grangetown — where the original clayware runs out under the back garden and joins a shared drain serving the whole row. That detail matters more than people realise, because it usually decides who pays.

Since 1 October 2011, most private sewers and lateral drains connecting to the public network in this area transferred to Dŵr Cymru Welsh Water. Their own guidance is that pipework collecting waste from your property alone, inside your boundary, stays yours — but pipes running beyond your boundary, and pipes shared with neighbours, are probably theirs. On a terrace that is very often the exact pipe that has blocked. We will tell you when we think a blockage sits on Welsh Water's side so you can report it to them rather than pay us to clear it.

The other Cardiff-specific factor is the combined sewer network under the older parts of the city, which carries foul and surface water in one pipe. During heavy rain those runs surcharge, and the first sign is often a gully backing up or a downstairs toilet gurgling — a symptom of the system being full rather than of anything blocked on your property. Highway gullies in the street are Cardiff Council's responsibility, not Welsh Water's and not yours.