Blocked Drains & Drain Unblocking

In short: A blocked drain is almost always one of four things: fat and food waste, wipes and sanitary items, tree roots, or a pipe that has cracked or sunk. Rods or a high-pressure jetter clear most of them in one visit, and a camera finds the cause when a drain keeps blocking. Network Drains provides 24 hour drain unblocking, and you speak to the engineer directly.

Drains don't block overnight. Most blockages build for weeks or months: a layer of grease here, a wipe snagged on a joint there, until one day the water has nowhere left to go. That's why the first sign is usually small, a sink that takes a little longer to empty or a gurgle from the bath when the toilet is flushed, and why it's worth acting before the drain stops completely.

This guide covers what actually causes blocked drains, how to tell where the blockage is, what's safe to try yourself, and what a professional drain unblocking involves.

What causes a blocked drain?

• Fat, oil and grease. Poured down the sink warm, it sets hard further along the pipe and catches everything that follows.
• Wipes and sanitary products. Even wipes sold as flushable hold together far longer than toilet paper and collect at bends and joints.
• Tree and shrub roots. Roots find the moisture at a leaking joint, grow through it and form a mat that traps waste.
• Damaged pipework. A cracked, collapsed or sunken section creates a ledge or dip where debris settles.
• Silt, leaves and garden debris. Mostly a problem for outside gullies and surface water drains.

Where is the blockage? A quick check

If only one sink, bath or toilet is slow, the blockage is probably in that fitting's own waste pipe, close to the plughole or pan. If several fittings on the ground floor are slow, or the downstairs toilet rises when you run an upstairs tap, the blockage is further down, in the underground drain. Lifting the nearest manhole cover tells you more: a chamber full of water means the blockage is downstream of it; an empty chamber means it's somewhere between the house and that cover.

What you can safely try first

For a single slow sink or bath, a plunger and a clean of the trap under the sink fixes a lot of blockages. Boiling water can loosen a light grease build-up in a kitchen waste, but not in a plastic trap that's already full. What we'd avoid is pouring in one chemical unblocker after another: they rarely shift a solid blockage, they can damage older pipes and seals, and they leave a caustic pool for whoever clears the drain afterwards. If the water is rising rather than falling, or sewage is involved, stop and call.

How professional drain unblocking works

We start by finding the blockage, usually by checking which fittings and manholes are affected. Most blockages are cleared with drain rods, which push through and break up the obstruction, or with a high-pressure jetter, which cuts through grease and roots and flushes the debris away along the whole pipe. If the same drain has blocked before, a CCTV drain survey shows whether there's damage behind the problem, so it gets fixed rather than cleared again in a month.

How much does drain unblocking cost?

The price depends on where the blockage is, what's causing it and how long it takes to reach. A blocked sink waste cleared in the kitchen is a smaller job than a long outside run that needs jetting and a camera. We talk through the likely cost on the phone before we attend, and if anything changes once we see it, we tell you before carrying on.

Is a blocked drain your responsibility?

Usually you're responsible for the drain pipes that serve only your property and sit within your boundary. Once a pipe is shared with a neighbour or runs outside your boundary, it's normally the water company's, following the 2011 transfer of private sewers in England and Wales. Our guide on who pays for a blocked drain explains how to tell the difference, and we'll say honestly if a blockage isn't yours to pay for.

Questions people ask