Kitchen Sink Blocked - How to Unblock It Safely in Bishops Stortford

Published April 2026 | Kitchen Sink Blocked How to Unblock It Safely

This guide walks you through how to safely unblock a kitchen sink using tools and methods that work for most common blockages. It's written for homeowners in Bishops Stortford and across Hertfordshire who want to try a sensible DIY fix before picking up the phone to a plumber.

Before you start - safety first

A blocked kitchen sink is one of the most common plumbing complaints our engineers deal with. Before you reach for a plunger or pour anything down the drain, take a moment to understand what you're dealing with and what to avoid.

Do not use boiling water on plastic waste pipes. Most modern kitchens - including the majority we see in Bishops Stortford properties built after the 1980s - use white plastic PVC pipework beneath the sink. Boiling water can soften or warp these pipes and loosen the push-fit joints that hold them together. Use hot water from the tap, not boiling water straight from a kettle.

Avoid mixing chemical drain cleaners. Products like Mr Muscle Drain Unblocker, HG Liquid Drain Unblocker, and Buster Kitchen Plughole Unblocker are fine used alone, but mixing different chemical products can produce dangerous fumes. If one product hasn't worked, flush the sink thoroughly with cold water before trying anything else.

Protect yourself. Wear rubber gloves throughout. If you're using any chemical product, open a window or make sure the kitchen is well ventilated. Blocked drains can harbour bacteria, and chemical drain cleaners are caustic enough to irritate skin and eyes.

Check the waste connections. If you have a dishwasher, its drain typically connects to the kitchen sink waste pipe. A blockage in the sink can back up into the dishwasher too. If both appliances are draining slowly, the blockage is likely in the shared waste pipe or the trap directly below the sink.

One more thing: if there's standing water in the sink, don't remove it before reading through these steps. That water can actually help you test whether your plunger is working properly.

What you will need

You don't need specialist tools to clear most kitchen sink blockages. Here's what to gather before you start.

Tools:

• A rubber cup plunger - the flat-bottomed type, not a toilet plunger
• A bucket and a few old cloths or towels
• A pipe wrench or adjustable pliers (if you need to remove the trap)
• A flexible drain snake or drain auger - optional but useful, available from Screwfix or B&Q for around 15 to 25 pounds

Materials:

• Washing-up liquid
• Bicarbonate of soda and white vinegar
• A chemical drain cleaner such as HG Liquid Drain Unblocker or Buster Kitchen Plughole Unblocker, typically 5 to 12 pounds from supermarkets or hardware shops
• PTFE tape, in case you need to refit the trap

Time estimate: Allow 30 to 60 minutes for a first attempt. If the blockage is deep in the pipework, it may take longer, or you may need to bring in a professional.

Step-by-step instructions

Step 1 - Remove debris from the drain opening

Use a cup or jug to scoop out the bulk of any standing water, then pull out the drain cover or filter basket if your sink has one. Clear out any visible debris sitting right at the drain - food scraps, grease build-up, and accumulated residue are all common culprits. This alone sometimes resolves a slow drain, particularly in kitchens that don't have a fine mesh filter basket fitted.

Step 2 - Try hot water and washing-up liquid

This is the simplest method and works well for grease-based blockages, which are the most frequent cause of kitchen sink problems. Boil your kettle, then let it cool for two or three minutes - you want very hot water, not boiling. Add a generous squirt of washing-up liquid directly into the drain. Slowly pour in around one litre of the hot water. Wait three to five minutes, then run the hot tap to see if the water flows freely. If it does, you're done. If not, move on to the next step.

Step 3 - Use a plunger

Fill the sink with a few centimetres of water if it isn't already. Place the plunger cup directly over the drain opening so it creates a seal against the sink base. Push down firmly, then pull up sharply - the idea is to create suction that dislodges the blockage. Do this 10 to 15 times in quick succession, then remove the plunger and check whether the water drains. Repeat two or three times if needed.

If your sink has an overflow hole (a small hole near the top rim of the basin), cover it with a wet cloth before plunging. This prevents you from losing suction through the overflow opening, which makes the plunger significantly more effective.

Step 4 - Use bicarbonate of soda and vinegar

If plunging hasn't fully cleared the blockage, this method can help break down organic matter and grease residue. Pour half a cup of bicarbonate of soda directly into the drain, followed immediately by half a cup of white vinegar. You'll hear a fizzing reaction - that's exactly what you want. Cover the drain with the plug to keep the reaction working inside the pipe rather than foaming out into the sink. Wait 20 minutes, then flush through with hot water from the tap.

Step 5 - Apply a chemical drain cleaner

If the previous steps haven't worked, a purpose-made chemical drain cleaner is your next option. Products like HG Liquid Drain Unblocker or Buster Kitchen Plughole Unblocker are widely available across Hertfordshire in supermarkets and DIY stores. Follow the label instructions exactly - most products ask you to pour a measured amount into the drain, leave it for 15 to 60 minutes, and then flush with water.

Do not use chemical cleaners repeatedly if they aren't working. If the first application hasn't shifted the blockage, there's likely a more solid obstruction further along the pipe that chemicals alone won't dissolve.

Step 6 - Remove and clean the trap

The P-trap - the curved U-shaped section of pipe beneath your sink - is where blockages most commonly accumulate. Removing and clearing it yourself is well within most people's ability. Place a bucket beneath the trap before you start, then unscrew the two plastic collar nuts where the trap connects to the waste pipe. Most modern plastic traps can be loosened by hand; if they're stiff, use adjustable pliers wrapped with tape to avoid marking the plastic.

With the trap removed, clear out any build-up inside it - compacted food particles, grease, and debris are typical. Rinse it under the tap. While it's off, feed a flexible drain snake or a straightened wire coat hanger into the section of pipe that runs into the wall to check for blockages further along. Refit the trap with the rubber washers seated correctly, hand-tighten the collar nuts, then run the tap and check for any leaks at the joints.

Step 7 - Test and flush

Run the cold tap at full pressure for 30 seconds, then switch to the hot tap for another 30 seconds. The water should flow freely with no pooling in the basin. If it drains well, the blockage is cleared. It's worth running a diluted washing-up liquid flush every few weeks as a preventative measure - it takes 30 seconds and significantly reduces grease build-up over time.

What to do if this does not fix it

If you've worked through all seven steps and the sink is still draining slowly or not at all, the blockage is most likely further along the external waste pipe - beyond the reach of standard household tools. In older properties around Bishops Stortford, clay drainage pipes can develop root intrusion or partial structural damage that produces exactly the same symptoms as a straightforward internal blockage.

You can hire a longer manual or electric drain snake (sometimes called a drain rod set) from a tool hire shop - HSS Hire and Speedy Services both have locations in Hertfordshire. These can reach 15 to 20 metres into the pipe. However, if you're not confident using one, it's possible to worsen a partial blockage by packing it tighter, or to disconnect a pipe joint inside the wall.

A CCTV drain survey is the most reliable way to diagnose a persistent blockage. Our engineers use the Voltrade GoFIX diagnostic process to quickly determine whether a blockage sits in the internal waste system or the external drain, which can save a lot of unnecessary investigation time and cost. A CCTV drain survey typically costs between 80 and 180 pounds depending on the access point and pipe length involved.

When to stop and call a professional

Some situations need a trained plumber rather than a DIY fix. Stop and call a professional if any of the following apply:

• Water is backing up into your dishwasher, or the sink is overflowing onto the floor
• You can smell sewage coming from the drain - this suggests the blockage may be at mains drainage level, not just in your kitchen waste pipe
• More than one drain in the house is blocked at the same time, such as the kitchen sink and the bathroom basin - this points to a shared drain problem rather than a localised blockage
• You've removed the trap and found no blockage in it, meaning the obstruction is further inside the wall or in the external drain
• The trap or waste pipes show signs of cracking, corrosion, or active leaking - these need replacing properly rather than being worked around

A local plumber in Bishops Stortford will typically charge between 60 and 100 pounds as a call-out fee for a standard blocked drain, with most kitchen sink jobs completed within an hour. For out-of-hours or emergency callouts, expect to pay between 150 and 300 pounds depending on the time and the complexity of the job. Don't delay if there's water pooling on the floor - water damage inside kitchen cabinets escalates quickly and can lead to mould growth, damaged flooring, and swollen cabinet bases that cost far more to repair than the original plumbing job.

Questions about this process

Can I use a drain snake on a kitchen sink without damaging the pipes?

Yes, in most cases a manual flexible drain snake is safe to use in standard kitchen waste pipes, including plastic PVC pipework. Insert it gently and rotate it as you feed it in rather than forcing it. Avoid using a motorised drain snake yourself unless you're confident with the tool, as these can crack older or corroded pipes if used at the wrong angle or with too much pressure. If in doubt, a plumber can clear a kitchen drain blockage safely for around 80 to 150 pounds in most cases.

How often should I clean my kitchen sink drain to prevent blockages?

For most households, a monthly hot water and washing-up liquid flush is enough to keep grease from building up in the trap and waste pipe. If your household cooks regularly with oils and fats, doing this weekly takes very little effort and makes a real difference over time. A bicarbonate of soda and vinegar treatment once a month adds another layer of protection. The single most important habit is to avoid pouring cooking fat or oil down the drain at all - even small amounts accumulate and are a leading cause of the kitchen sink blockages our engineers clear in Bishops Stortford every week.

What causes a kitchen sink to smell even when it is draining normally?

A sink that drains fine but produces a persistent bad smell is typically caused by organic build-up inside the trap or waste pipe - food residue and grease breaking down slowly over time. Cleaning the trap as described in Step 6 usually resolves it. If the smell returns quickly, the issue may be a failing drain vent or a trap that's drying out due to infrequent use. Running the tap for a few seconds every couple of days keeps the trap water seal intact, which is what blocks sewer gases from rising up into the kitchen.