Can Coffee Grounds Go Down The Sink? Here’s What Really Happens

Can coffee grounds go down the sink? We’ve been asked so often that we felt the need to put the extremely simple answer down in writing:

No!

Coffee shouldn’t be washed down the drain under any circumstances – it’s just that simple. It might look harmless when it disappears with the water – out of sight, out of mind – right? Wrong.

Inside your plumbing, it hasn’t just innocently flowed away or dissolved. Far from it. And once we explain why, the risks become obvious – and it’ll be easy to see how a small kitchen habit can turn into a major blockage.

So here we go – the main reasons coffee grounds cause problems, followed by a look at some similarly bad kitchen habits that quietly damage drains as well.

5 Reasons you should never put coffee grounds down the sink

Here’s what really happens inside your plumbing when coffee grounds go into the drain – and why they cause persistent blockages.

1. Coffee grounds don’t dissolve – they clump

A big misconception is that grounds wash away like sugar or dissolve like salt.

They don’t.

Even fine particles behave like grit and settle in the bends of the pipe. Over time, they form dense sludge that water struggles to carry. We’re often called out after people try to solve it themselves by searching how to dissolve coffee grounds in drain – unfortunately, nothing you buy at the shops will break them up once they’ve compacted. You’ll need pro help!

2. They mix with grease and fats to form a block

Even in tidy kitchens, a small amount of oil, butter, or cooking residue ends up in the plumbing line. When coffee grounds meet these fats, the result is a sticky, cement-like paste.

This is one of the most common causes of slow kitchen drains. It’s also why coffee grounds in sink issues tend to appear suddenly – the pipe can look fine one day and be almost fully blocked the next. As this buildup starts to break down, it often creates a lingering kitchen sink smell long before a complete blockage forms.

3. They collect in the P-trap and slow everything down

All kitchen sinks have a P-trap designed to hold water and stop smells. It’s also the first point where sediment settles.

Grounds often build up here first, which creates a partial blockage that gets worse every time more coffee is tipped in. Many people don’t realise the problem started months earlier with the occasional scoop of coffee grounds down sink holes.

4. Older Brisbane pipes are especially vulnerable

Many homes around Brisbane still have older clay or mismatched pipework. These lines have rough internal surfaces – making it even easier for coffee grounds to snag and pile up.

Once a layer sticks, more follows – and eventually the whole line can clog. It’s a simple mistake, but we see it almost every week across Brisbane Northside, Southside and the bayside suburbs. Unfortunately.

5. Recurring blockages become almost guaranteed

Once coffee grounds settle in a kitchen plumbing line, they trap:

• Soap scum
• Food scraps
• Grease

This causes ongoing problems even after you think the drain is clear. The smallest leftover pocket becomes a magnet for new debris. That’s why professional jetting or mechanical cleaning is often the only long-term fix.

Other kitchen habits that damage your drains

Coffee grounds are only one part of the story. A few other everyday sins that you may also be committing on a daily basis also create blockages – especially when combined with Brisbane’s older pipe networks and heavy wet seasons.

Cooking oils and fats: Hot water might wash them away briefly, but further down the line, they cool, harden and trap anything that passes by.

Rice and pasta: These swell with water and glue themselves to the inside of the pipe.

Eggshells: The thin membrane sticks to grease, creating little “nets” that catch more debris.

Food scraps: Even tiny bits build up over time, especially in kitchen lines with slight dips or older joints.

Small habits like these are why kitchen drains tend to be the first plumbing lines to block in many Brisbane homes.

How to prevent coffee-related blockages

Don’t stress too much, because you actually don’t need to change much – just build small habits that help your drains stay clear:

• Put used grounds in the bin or compost
• Wipe pans with a paper towel before washing
• Use a sink strainer to catch finer particles
• Rinse with hot water only after food debris is removed
• When in doubt, keep solids out of the sink entirely.

When it’s time to call a plumber

Be honest. Is your drain:

• Running slowly?
• Gurgling?
• Giving off a sour smell?

We hate to break it to you, but there’s already build-up in the line – there’s just no getting around it.

Coffee grounds are a common culprit, but grease, food scraps and collapsed pipe sections can be part of the problem too. Luckily, a CCTV drain inspection shows exactly what’s going on – and hydro-jetting clears the entire line so it flows properly again. And there are plenty of other drain cleaning tools, techniques and tricks that a great plumber will have up their sleeve as well.

Need your kitchen drain cleared fast?

Here at Brisbane Drain Cleaning, we handle everything – from stubborn kitchen sink blockages to full stormwater and sewer cleaning. And we do it all with fixed upfront pricing and same-day service across Brisbane and beyond.

Can you put coffee grounds down the sink? No! What you can do is book online or call now for a straightforward quote and reliable, friendly service.