How Much Does It Cost to Unblock a Sink? Kitchen vs Bathroom

What it costs to unblock a sink depends on how far along the pipe the blockage is. Most blocked sinks are blocked in the trap directly under the bowl, which is a short job and often one you can do yourself. The price goes up when the blockage is further along the waste pipe, inside a wall or under a floor, or in the gully and drain outside. A kitchen sink and a bathroom basin also block for different reasons, which changes what a lasting fix involves and what it costs.

What decides the cost of unblocking a sink?

The location of the blockage, what it is made of and the time you book are what set the price. A trap blockage is the cheapest; a blockage in a long or boxed-in waste run, or in the drain outside, costs more because it needs more access and different equipment.

The trap is the U-bend or bottle trap under the sink. Hair, soap and food build up there first, and it can be unscrewed and cleaned by hand. Beyond the trap, the waste pipe runs to a soil stack or out through the wall to a gully. If the blockage is along that length, an engineer will rod or jet it from an access point, and if the pipe is boxed in or runs under a floor, reaching it takes longer.

Our rate card splits prices into three time bands: standard hours, evenings and nights. A blocked sink is inconvenient, but it is rarely an emergency when there is another sink or basin in the property, so booking in standard hours is usually the cheapest choice.

Kitchen sink or bathroom basin: why the price differs

A bathroom basin usually blocks with hair and soap in the trap, and clearing it is normally a quick job. A kitchen sink usually blocks with fat, oil and food waste that coats the whole waste pipe, so a proper fix may mean clearing the full run rather than just the trap.

Fat poured down a kitchen sink cools and sticks to the inside of the pipe, gradually narrowing it until food scraps catch and block it. Clearing the trap brings the flow back for a while, but the narrowed pipe blocks again. On a kitchen run that keeps blocking, high-pressure jetting the waste pipe and the gully cleans the pipe back to its full bore, which costs more on the day and usually saves repeat visits.

Our guide to why a sink drains slowly goes through the common causes if yours is sluggish rather than fully blocked.

What you can safely try before paying anyone

For a blocked sink, a plunger and a cleaned trap fix a large share of cases, and neither costs anything beyond the tools. It is worth trying both before you book.

Block the overflow with a damp cloth, then plunge the plughole firmly for a minute. If that does not work, put a bowl under the trap, unscrew it by hand, and clear out what has collected inside. Check the washers are seated properly when you screw it back on, then run the tap and look for drips.

Be careful with chemical drain cleaners. They can work on a slow basin with a little hair in it, but they rarely shift a solid blockage, and a sink full of caustic water is dangerous for whoever has to open the trap afterwards. If you have used one, tell the engineer before they start.

When a blocked sink is really a blocked drain

If the sink and other fittings are slow, or water comes up in the outside gully when the sink drains, the blockage is in the drain rather than the sink. That is priced as drain clearance, not sink unblocking.

Many kitchen sinks in London houses discharge into a trapped gully outside the back wall. Leaves, fat and silt collect in that gully and block it, so the sink backs up even though its own pipe is clear. Look at the gully before calling anyone: if it is full of standing water, the problem is there or further down. Clearing a gully and the drain beyond it is covered on our drain clearance page.

What pushes the cost up

The price rises when the pipe is hard to reach, when the blockage keeps coming back, or when the waste pipe itself is faulty. These are the points to raise when you ask for a quote.

Hidden pipework. Waste pipes boxed in behind kitchen units, run under a floor or through a wall need more time to access and to reassemble afterwards.

Shared waste runs. In a flat, the kitchen waste may join a shared stack. If the blockage is in the shared stack, it is usually the freeholder's or managing agent's responsibility rather than yours.

Poor falls or faulty pipe. A waste pipe laid with too little slope, or with a sag, will keep catching debris. Clearing it helps for a while; correcting it is a small plumbing job that is priced separately.

How to compare sink unblocking quotes

Ask what the price covers, where the blockage has to be for that price to apply, and what happens if it turns out to be in the drain outside. Two quotes for 'unblocking a sink' can describe very different amounts of work.

Check whether the price is fixed or charged by time, whether VAT is included, and whether jetting the waste run is part of it or an extra. A company that explains those points before arriving is one whose invoice will match what you were told. Tell us what the sink is doing and whether other fittings are affected, and we will confirm which rate applies before we attend.

For how drain unblocking is priced more generally, see our guide to how much drain unblocking costs in London.