Before you call anyone out, most single-drain blockages are worth trying yourself first — it takes ten minutes and costs nothing. Here's what actually works, safely, and the signs that mean you should stop and call a specialist instead.
Pour hot water down the drain in stages, pausing about 10 seconds between pours. Works best on grease, fat, and soap build-up. Never use boiling water on plastic (PVC) waste pipes — it can warp the joints. Hot from the tap is safe; straight off the boil isn't.
Pour baking soda directly down the drain, follow with vinegar — it'll fizz immediately. Leave it to sit for at least an hour, then flush through with hot (not boiling) water. Works well for mild kitchen and bathroom sink blockages.
Seal any overflow opening with a damp cloth first, so you get full pressure at the blockage. Place the plunger directly over the plughole and pump firmly several times. Good for hair and soap-scum blockages.
Under most sinks there's a U-bend (trap) that catches debris. Put a bucket underneath, unscrew the trap by hand or with adjustable pliers, and clear out anything solid. Messy but usually effective for anything the plunger didn't shift.
Clear visible debris — leaves, mud, litter — from the drain cover first. Use drain rods to break up the blockage, pushing and twisting clockwise (twisting the other way can unscrew the rod sections underground, which is a genuinely annoying way to lose a rod).
Call a specialist instead of continuing to DIY if: water is backing up rather than draining slowly, more than one drain in the house is affected at once (usually means the blockage is further down the shared pipework, not fixable from a single sink), it's a toilet (drain rods and plungers can push the blockage further in or damage the pan), or the same drain keeps blocking within weeks of clearing it — that's a sign of a structural cause a CCTV survey would find, not something repeat plunging fixes.
Sparingly, and not repeatedly. Chemical cleaners can damage older pipework with repeated use, and they're genuinely dangerous if you later need a plumber to work on the drain by hand. If hot water, baking soda/vinegar, or a plunger hasn't worked, it's usually better to call a specialist than to keep escalating chemicals.
DIY methods and safety notes sourced from UK trade-site research on 2026-09-04 (see docs/supporting-content-plan.md) — not fabricated advice.