Clearing Blocked Drains

Clearing a blocked drain is not a single technique — it is a diagnosis followed by the correct tool for what the diagnosis reveals. A straightforward grease blockage in a kitchen drain requires something quite different from a root-mass in an outdoor clay run or a collapsed section of pipe. Understanding how engineers approach different blockage types makes it easier to know what to expect when we arrive.

The First Step: Locating and Identifying the Blockage

Before clearing anything, we locate the blockage and assess its nature. For most household blockages — a slow kitchen sink, a backed-up toilet, a flooded gully — the location is reasonably obvious from the symptom pattern. A single slow fixture usually points to a blockage in the waste pipe serving that fixture. Multiple fixtures backing up simultaneously points to a blockage further down in the shared drain run or the main soil stack.

For less clear-cut cases, particularly recurring blockages or outdoor drain problems, we use CCTV camera inspection to see inside the pipe before deciding on a clearing method. The camera reveals whether the blockage is a soft accumulation (grease, silt, hair) that jetting will shift in one visit, or something structural — a root mass, a displaced joint catching debris, or a partially collapsed section — that needs a different approach.

High-Pressure Water Jetting

Jetting is the primary clearing method for the vast majority of drain blockages. A high-pressure pump forces water through a specialist nozzle at pressures of up to 4,000 psi. The forward-facing jets drive the nozzle through the blockage, and the rearward-facing jets scour the pipe walls clean as the hose is withdrawn.

The difference between jetting and rodding is significant. A drain rod punches a hole through a soft blockage and restores some flow — but it leaves the surrounding build-up on the pipe walls, which rapidly collects new debris and re-blocks. A jet clears the blockage and descales the pipe walls at the same time, leaving the inside of the pipe close to its original bore. The result is a drain that stays clear considerably longer after a jet than after a rod.

Jetting is effective on:

• Fat and grease accumulation (the most common blockage cause in kitchen drains)
• Hair and soap scum in bathroom waste pipes
• Silt and leaf debris in outdoor gullies and inspection chambers
• Scale deposits on pipe walls in older systems
• Loose root masses after root cutting

The nozzle head is selected to match the pipe diameter and the nature of the blockage. Soft accumulations use a standard forward-and-rear nozzle. Harder scale or grease requires a penetrating nozzle with higher forward pressure. We adjust pressure to the pipe type — high pressure is appropriate for robust uPVC or clay but can damage fragile older pipes, which is why camera assessment before jetting matters on aged systems.

Drain Rodding

Rodding involves feeding a series of flexible rods through the drain to physically push or pull the blockage material. It is a faster and lower-cost clearing method for accessible, straightforward blockages — a soil stack outlet that is clearly blocked with tissue and wipes, for example, or an inspection chamber where the blockage is visible.

The limitation of rodding is that it addresses the immediate blockage without cleaning the pipe walls. It is best used where the blockage is clearly a one-off (flushed wipes, a foreign object) rather than a progressive build-up. For recurring blockages or anywhere the pipe walls are known to carry grease or scale, jetting produces a better and more durable result.

Root Cutting

Tree and shrub roots enter drain pipes through hairline cracks in clay joints. Once inside, they grow progressively and create a mesh that catches tissue and debris, eventually blocking the pipe entirely. Rodding cannot shift established root masses — the rods flex around the roots rather than cutting through them.

Root cutting uses a high-speed mechanical cutting head fed through the drain on a flexible drive shaft. The rotating blades cut through the root mass and break it into fragments that are then flushed out by jetting. Root cutting clears the immediate obstruction, but it does not seal the crack that allowed the roots to enter. Without sealing the entry point — using a patch liner or full CIPP relining — roots regrow and the drain blocks again within one to two growing seasons.

For any drain with confirmed root intrusion, we recommend root cutting followed immediately by lining. It is the only permanent solution rather than an annual clearing cycle.

After Clearing: Confirming the Result

After clearing, we check the flow by running water through the system and, on more significant jobs, we run the camera again to confirm the pipe is clear and inspect the pipe walls for any damage that the blockage may have been masking. Clearing a drain sometimes reveals a structural issue — a crack that the blockage was covering, or a displaced joint that was retaining the debris — that needs follow-up work to prevent an immediate recurrence.

London Drain Clear Ltd clears blocked drains across Enfield, Barnet, Edgware, Wembley, Cheshunt, Potters Bar and Southgate, 24 hours a day. If you have a blocked drain, contact us via the enquiry form and we will attend the same day.