Unblocking drains outside: a step-by-step fix guide

Unblocking drains outside is one of the most common jobs homeowners try to tackle themselves before calling a professional, and in most cases it's the right call — a straightforward blockage in an external gully or manhole can usually be cleared with a set of drain rods and half an hour of unpleasant work. This guide walks through the exact method a drainage engineer would use, in the order they'd use it, so you can either fix it yourself or at least understand what's happening before you pick up the phone.

We'll cover how to confirm where the blockage actually is, what to have ready before you start, how to work rods safely, the difference between rodding, jetting and bailing, cost expectations if you do end up calling someone in, and the warning signs of a collapsed drain — the point at which DIY stops helping and starts making things worse.

An outside drain is the external gully or manhole that carries wastewater away from your kitchen, bathroom and downpipes into the main sewer. When it blocks, the signs usually appear inside the house first: sinks that drain slowly, gurgling from the toilet when you run a tap elsewhere, or an unpleasant smell drifting up from the plughole.

The clearest confirmation is outside. Lift the cover on the nearest manhole or gully at the side or back of the property. If it's full of standing water or debris right up to the top, the blockage is between that chamber and the main sewer. If it's empty but the chamber further upstream is full, the blockage is somewhere between them.

In most Northamptonshire homes we get called out to, the cause is one of four things: fat and food waste that solidifies in the pipe after being poured down the kitchen sink; wet wipes, sanitary products and other items that shouldn't be flushed but often are; a build-up of leaves, silt and moss washing down from gutters into the gully; or tree root intrusion, which is especially common in older Victorian and Edwardian clay pipework where roots find their way in through the joints.

Recurring blockages are almost always a sign that one of these underlying causes hasn't been dealt with — clearing the immediate blockage helps for a few weeks, but the same thing builds up again.

Before you attempt to clear it, put on heavy-duty rubber gloves and old clothes you don't mind ruining. Have a bucket, an old towel and a strong pair of drain rods to hand — you can buy a set of screw-together rods with a plunger and corkscrew head from any DIY shop for around £25. Don't use bleach or caustic chemical drain cleaners on external drains: they rarely shift a real blockage, they're dangerous around your skin, and they make life much harder for a professional if you end up calling one anyway.

There are three ways to physically clear a blocked outside drain, and homeowners can realistically do one of them. Rodding is the DIY option: manual push-pull force delivered through a series of screw-together fibreglass rods, tipped with a rubber plunger or corkscrew head. Rods work well for soft blockages within about four metres of the chamber you're feeding them into — grease, wet wipes, leaves and light silt.

High-pressure water jetting is the professional option. A jetter delivers water at 3,000+ psi through a nozzle that scours the full inner wall of the pipe, not just a channel through the middle. Jetting removes what rods leave behind — a thin greasy film that reforms into a full blockage within weeks — and it can reach much further down the run. It's not a homeowner tool: the water pressure is genuinely dangerous, and misdirected it will cut through skin.

Bailing — literally scooping standing water out of a full chamber before you start — is the unglamorous step in between. If the chamber is overflowing, bail it down first with a bucket so you can see what you're rodding into and so waste water isn't spraying every time you push. It also stops raw sewage backing up further into the house while you work.

1. Lift the drain cover using a screwdriver as a lever if needed, and set it aside safely. Wear gloves — the underside is not pleasant.

2. If the chamber is full, bail it down with a bucket before you start rodding. You want to be able to see the pipe openings on each side of the chamber.

3. Screw the rods together as you go, attaching the plunger head first. Feed them down into the drain in the direction of the blockage — that's away from the house, towards the main sewer.

4. Push and pull the rods, rotating them clockwise as you go. Only ever rotate clockwise — if you rotate anticlockwise, the sections can unscrew inside the pipe, and now you have a blockage and a stuck set of rods.

5. You'll usually feel the blockage give way — the water level in the chamber will drop quickly. Once it clears, run a hose or several buckets of water through to flush the line.

6. If plunging doesn't shift it, swap the plunger head for the corkscrew attachment and try again — this is better for solid material like wet wipes or root debris.

A blockage clears. A collapsed drain doesn't — and every time you try, you risk making the damage worse. There are four warning signs that what you're dealing with is structural, not just a clog:

The same chamber blocks again within days or weeks, no matter what you clear from it. Waste isn't sitting there because something's stuck; it's sitting there because the pipe downstream has partially collapsed and can't carry it away.

There's a soft or sunken patch in the lawn, driveway or paving along the drain run. Waste water leaking from a broken pipe washes soil away underneath the surface, and sooner or later the ground drops.

Rats appear in the garden. A cracked or collapsed pipe is an open invitation — rats travel along the sewer network and exit wherever the pipework is broken.

Rods hit something solid a metre or two in and won't go any further. On a healthy drain you can push rods along the full run to the next chamber; hitting an immovable obstruction usually means the pipe has partially caved in.

If any of these apply, stop rodding. You need a CCTV camera survey to see what's actually going on before anything else — trying to force a blockage through a collapsed section will just push debris into the void and make the eventual repair bigger.

There are three situations where DIY becomes the wrong tool: you can't reach the blockage with rods (usually more than about 4 metres in); the blockage keeps returning within days or weeks; or you can see sewage backing up into the property. In any of those cases, keep going and you'll usually just spread the problem further down the line — or damage the pipe.

A professional will use CCTV to see exactly where the blockage is and what's causing it, then either high-pressure jet it clear (which cleans the full pipe wall, not just a channel through the middle) or, if a section has collapsed or been damaged by roots, quote for a patch repair or lining. That's a lot cheaper than digging up your driveway to find out what's wrong.

If your property is in Northamptonshire or one of the surrounding counties we cover, our fixed call-out fee covers the first hour on site — diagnosis, rodding or jetting where suitable, and a CCTV camera check within that first hour if we need one, with no hidden costs. Call us for a straight price over the phone.

Prices for unblocking drains outside vary widely across the UK. National franchises typically start with a low advertised call-out and then add per-hour labour, jetting surcharges, CCTV fees and out-of-hours premiums — a bill that starts at £80 can easily reach £400 by the time the invoice lands. Independent local firms tend to be cheaper and more transparent, but quality varies.

The single most useful question to ask before anyone drives out is: what does the quoted price actually include? A fixed call-out fee that covers the first hour on site — including diagnosis, rodding or jetting where suitable, and a CCTV check within that hour if needed — is the fairest structure for a homeowner, because you know exactly what you're paying for and you don't get billed extra for the engineer identifying the cause. That's how we charge, and it's what we'd recommend asking for from anyone you're considering.

The two real risks when unblocking drains outside are bacterial contamination and eye injury from splashback. Wear heavy-duty gloves that go past your wrist, safety glasses or a face shield if you can, and long sleeves. Never eat, drink or touch your face while you're working. Wash hands, arms and any exposed skin thoroughly with hot soapy water once you're done, and put the clothes you were wearing straight in the wash on a hot cycle — don't sit around in them afterwards.

Never lean over a manhole with your face directly above the opening: if the blockage gives way suddenly under rod pressure, contaminated water can spray up. And keep children and pets well away — an uncovered chamber is a serious drop hazard, and neither of them will read the same signs you did.

Never pour fats or oils down the kitchen sink — let them cool and put them in the bin. Only flush the three P's (pee, paper, poo) — wet wipes labelled 'flushable' are one of the biggest single causes of blockages we see. Clear leaves out of gutters at least once a year to stop them washing down into gullies. And if you have a large tree within about 10 metres of your drain run, particularly on an older property with clay pipework, consider a one-off CCTV survey — catching root intrusion early is a lot cheaper than dealing with a collapsed pipe later.