How to unclog a drain is one of those jobs every homeowner, tenant and landlord ends up googling at the worst possible moment, usually with water rising in the sink. The good news is that most blockages in a kitchen or bathroom sit within reach of a plunger and twenty minutes, and the ones that do not have clear rules about who is responsible for fixing them. This guide explains the safe methods in order, when to stop and call a plumber, where a private drain ends and Scottish Water’s sewer begins, and what the Repairing Standard means for landlords and tenants in Scotland.

How do you unclog a drain?

Most sink and shower blockages are hair, soap scum and cooking fat sitting in the trap (the U-bend) or the first metre of pipe. Those clear easily. A blockage further along, or one affecting the toilet and the bath at the same time, is usually in the shared pipework or the drain outside, and that is a different job.

How to unclog a drain, step by step

1. Clear what you can see. Lift out the plug or strainer, pull out any hair or food at the top of the drain, and run the hot tap for a minute. Surprising numbers of “blocked” sinks are fixed here. For a kitchen sink, scrape plates into the bin first so you are not adding to the problem.
2. Use a plunger properly. Block the overflow with a wet cloth, add enough water to cover the rubber cup, then pump firmly ten to fifteen times before pulling away sharply. The pressure, not the force, shifts the clog. Use a cup plunger for sinks and baths and a flange plunger for the toilet, and keep them separate.
3. Snake it. A cheap plastic drain stick or a hand-cranked drain snake pulls out the matted hair and soap that plungers push past. Feed it in slowly, twist, and withdraw. Have a bag ready. Be gentle in older homes, where lead and cast-iron waste pipes do not take kindly to a metal snake.
4. Clean the trap. Put a bucket under the U-bend, unscrew the connectors by hand (no tools needed on most plastic traps), tip out the contents, rinse and refit. Check for drips after the first use. This clears the single most common blockage point in any bathroom.
5. Dissolve grease the gentle way. Pour a cup of baking soda down the plughole, follow it with a cup of white vinegar, cover for fifteen minutes and flush with a kettle of hot water. On a kitchen sink, hot (not boiling) water with washing-up liquid run for a few minutes also softens fat. Avoid boiling water in a toilet or on plastic pipes.
6. Know when to stop. If the blockage comes back within days, if more than one fixture is slow, if there is a sewage smell in the garden or water coming up through an outside gully, stop. Those are signs the problem is beyond the house, and repeated plunging or chemical cleaner will not fix it.

When the blockage is outside the house

In Scotland the pipework is private until the point where the drain leaves the boundary of your property (the curtilage) or joins a drain from a neighbouring property; from there it is a public sewer and Scottish Water’s responsibility, as its drains and sewers leaflet explains. In a block of flats the shared drains within the grounds stay private, so a blockage in the common stack is a common repair shared between the owners. Scottish Water says around 80% of blockages come from items flushed down the toilet or fat, oil and grease poured down the sink, which is why the fixes above are worth trying before anyone is called out. For a private drain beyond your reach, a licensed drainage contractor with a jetting unit is the right call; for a public sewer, report it to Scottish Water.

Landlords and tenants: who fixes a blocked drain in Scotland?

A private landlord in Scotland must keep the let to the Repairing Standard, which requires the structure and exterior, including drains, gutters and external pipes, to be in a reasonable state of repair and the installations for water supply and sanitation to be in reasonable repair and proper working order. A sink that will not drain or a toilet that backs up is a Repairing Standard issue, and the landlord has to put it right within a reasonable time once told. Tenants should report it in writing, with photos and the date, so there is a record; Citizens Advice Scotland suggests asking for a response within 14 days. If nothing happens, a tenant can apply to the First-tier Tribunal for Scotland (Housing and Property Chamber). The flip side is that a blockage caused by what has gone down the drain, such as wipes, nappies or cooking fat, is damage rather than wear and tear, and most tenancy agreements let the landlord recover a reasonable cost from the tenant; check the wording of yours. Since 6 October 2026 damp and mould reports in Scotland also carry fixed investigation and repair timescales under Awaab’s Law, and a leaking or blocked drain is a common cause of both, so a managed property should treat a drainage report as urgent rather than routine. Our landlord compliance checklist and boiler pressure guide cover the other calls a landlord gets in winter.

Preventing the next one

Fit a mesh strainer in every plughole and empty it weekly. Pour cooled fat into a container for the bin, never the sink. Only toilet paper goes down the toilet; “flushable” wipes are the single biggest cause of blocked sewers. Once a month, run hot water and a little washing-up liquid through the kitchen sink for a few minutes. In a let, a one-line note in the welcome pack about wipes and fat saves more call-outs than any clause in the lease. Our guide to preparing a home for a Scottish winter has the rest of the seasonal list.

“Surely a bottle of chemical drain cleaner is quicker?”

Sometimes, and it is a fair shortcut for a slow bathroom sink. But caustic cleaners do nothing for a blockage of hair and wipes, they can damage older pipes and seals, and if the drain is fully blocked they leave a sink full of corrosive water that the plumber then has to work in. If you use one, follow the label, never mix products, and never plunge afterwards. For anything worse than a slow drain, the mechanical methods above are safer, cheaper and more likely to work.

Frequently asked questions

Who is responsible for a blocked drain in a rented house in Scotland?

The landlord, in almost every case. The Repairing Standard makes drains, external pipes and sanitation installations the landlord’s responsibility, and the repair must be done within a reasonable time of being reported. The exception is a blockage the tenant has caused by misuse, where the tenancy agreement will usually allow the landlord to recover a reasonable cost. Tenants should always report the problem in writing first. Our guide to letting agent fees in Scotland explains what a managed service handles for you.

Is a blocked drain Scottish Water’s problem?

Only once the pipe has left your property boundary or joined a neighbour’s drain; up to that point it is private. Within a block of flats the shared drains in the grounds remain the owners’ joint responsibility. If sewage is surfacing in the street or the garden from a public sewer, report it to Scottish Water; if the problem is between your house and the boundary, you need a plumber or drainage contractor.

Can I use boiling water to unclog a drain?

Hot water is useful for softening grease in a kitchen sink, but boiling water can soften and distort plastic waste pipes and crack a ceramic toilet, and it will not shift hair or wipes. Use water from the hot tap, or a kettle left to cool for a minute, and combine it with a plunger or drain stick rather than relying on heat alone.

How much does a plumber charge to unblock a drain?

Call-out charges vary by area and time of day, so get a price before anyone arrives and ask whether jetting is included. A simple internal blockage is usually a short visit; an external drain that needs a jetting unit or a camera survey costs more. For a let, a managing agent will have vetted contractors at agreed rates, which is one of the practical arguments for full management. See our landlord registration guide for the other costs of letting legally in Scotland.

Letting a property in Ayrshire or Glasgow?

Blocked drains, boilers and damp are the calls that test a self-managing landlord. Our fully managed service handles the reporting, the contractors and the Repairing Standard paperwork for you. Find out more about letting your property with Lomond, see our homes to let, or read more in our landlord and lettings guides.

This article is general information, not legal or financial advice. Property rules differ across Scotland and the rest of the UK and change over time; check the current position with a solicitor or the relevant council before acting. Last verified: 2 November 2026 against the Scottish Government’s Repairing Standard statutory guidance (in force from 1 March 2024), Citizens Advice Scotland (getting repairs done while renting) and Scottish Water’s drains and sewers leaflet.