DIY vs Professional Drain Clearance: When to Call the Experts

Before you spend £100+ on a professional, it's worth knowing which blocked drain problems you can realistically fix yourself — and which ones you'll only make worse by trying. We've put together a clear-headed guide based on what actually works, what doesn't, and when the sensible move is to pick up the phone.

What You Can Try at Home

These DIY methods work best on minor blockages close to the plughole — the kind where one fixture is draining slowly but everything else in the house is fine. Total cost: under £15 in most cases.

The Plunger (Success Rate: ~60% for Minor Blockages)

A sink or toilet plunger is still the most effective first line of attack for a simple blockage. The key is technique:

1. Fill the sink or basin with enough water to cover the plunger cup. You need water — not air — to create hydraulic pressure.
2. Block the overflow hole with a wet cloth. If you don't, the pressure you create just escapes through the overflow instead of pushing the blockage.
3. Place the plunger flat over the plughole and push down firmly, then pull up sharply. Repeat 15–20 times.
4. For toilets, use a flange plunger (the kind with an extended rubber lip), not a flat sink plunger. The flange creates a seal in the curved toilet bowl.

A plunger from any hardware shop costs £3–£8. If it doesn't work after two or three minutes of firm plunging, the blockage is likely too far down the pipe or too solid for this method.

Boiling Water and Washing-Up Liquid

For kitchen sinks specifically, a kettle of boiling water with a generous squirt of washing-up liquid can dissolve fresh grease blockages. Pour the liquid down first, wait five minutes, then follow with the boiling water. The detergent breaks up the grease and the hot water flushes it through.

This only works on grease. It won't do anything for hair, food solids, or blockages further down the system. And a word of caution: don't pour boiling water into a toilet bowl, as the thermal shock can crack the porcelain.

Baking Soda and White Vinegar

Pour half a cup of baking soda down the drain, followed by half a cup of white vinegar. Cover the plughole, wait 30 minutes, then flush with hot (not boiling) water. The fizzing reaction can help dislodge light organic build-up.

We'll be honest: this method is better at freshening a slow drain than clearing a genuine blockage. If water is sitting in the basin and not draining at all, baking soda and vinegar won't cut it.

A Drain Snake (Success Rate: ~40% for Hair Blockages)

A hand-operated drain snake (sometimes called a drain auger) is a flexible metal coil you feed into the pipe to physically break up or retrieve a blockage. They cost £8–£15 from B&Q, Screwfix, or Amazon, and work best for hair clogs in bathroom drains.

Feed the snake into the plughole and turn the handle clockwise as you push. When you feel resistance, keep turning — you're either breaking through the blockage or hooking onto it. Pull back slowly to retrieve the debris. You may need to repeat this several times.

Drain snakes work well on blockages within the first metre or so of pipe. Beyond that, a domestic snake doesn't have enough reach or power.

What NOT to Do

Some popular DIY approaches can actually make things worse — or damage your plumbing:

Chemical Drain Cleaners: More Harm Than Good

Products like Mr Muscle Sink & Drain or own-brand caustic drain unblockers contain sodium hydroxide (caustic soda) or sulphuric acid. They're widely available and heavily marketed, but most professional drainage engineers recommend against them for several reasons:

• They can damage pipes. Caustic chemicals generate heat as they react. In older clay, pitch fibre, or PVC pipes, repeated use can soften joints, crack pipes, and accelerate deterioration. A £3 bottle of drain cleaner can lead to a £500 repair.
• They often don't work. If the blockage is caused by tree roots, a collapsed pipe, or compacted debris, no amount of chemical will shift it. The chemical just sits in the pipe on top of the blockage, creating a hazardous situation for anyone who later needs to work on it.
• They're dangerous. Caustic soda causes serious chemical burns on contact with skin. If you've poured it down a drain and it hasn't cleared the blockage, the standing water is now a concentrated chemical solution. Any plumber or engineer who then works on that drain needs to be warned.

Pressure Washers Down Drains

We've seen DIY forums suggest using a domestic pressure washer (like a Karcher) to blast through blockages. Don't do this. Domestic pressure washers aren't designed for drain work and can force water back up through other fittings, push debris further into the system, or damage pipe joints. Professional drain jetting machines operate at controlled pressures with specialised nozzles — it's a different tool entirely.

Coat Hangers and Improvised Tools

Straightened wire coat hangers can scratch the inside of plastic pipes and push blockages deeper rather than pulling them out. If you're going to use a physical tool, spend £10 on a proper drain snake with a retrieving head.

When DIY Won't Work

Call a professional if any of these apply:

• Multiple fixtures are blocked or slow at the same time
• The external manhole is full or overflowing
• You can smell sewage inside the house
• The blockage keeps coming back within days of clearing it
• You've tried a plunger and drain snake without success
• The problem is in an external or underground drain

In all these cases, the blockage is either too deep, too severe, or caused by a structural problem (like root ingress or a cracked pipe) that no amount of DIY will fix.

What Professionals Do Differently

A professional drainage engineer brings two things you don't have: industrial equipment and diagnostic capability.

High-Pressure Water Jetting

The standard tool for clearing blockages is a jetting machine that pushes water through the pipe at pressures of 3,000–4,000 PSI (compared to roughly 2,000 PSI from a domestic pressure washer). The nozzle is designed to cut through grease, break up root masses, and scour the pipe walls clean. A typical residential drain can be jetted clear in 20–40 minutes.

CCTV Drain Surveys

If the cause of the blockage isn't obvious, engineers use a CCTV camera threaded into the pipe to see exactly what's going on. This reveals root ingress, displaced joints, cracks, scale build-up, and collapsed sections. The footage is recorded and you get a copy, which is useful for insurance claims or if you're buying a property and want to check the drainage.

A CCTV survey typically costs £100–£200 and many companies offer it as a bundle with the jetting work.

Cost Comparison: DIY vs Professional

The bottom line: if it's a single slow drain and you own a plunger, give it five minutes. If that doesn't work, or if multiple drains are affected, skip the guesswork and find a company that will give you a fixed price quote before starting work.