How to Fix a Slow Draining Sink (And Why It Shouldn’t Be Overlooked)

A clog in the drain and a slow draining sink is one of those issues that will only worsen unless you address it. After 15 years or so of having a plumber's licence and countless blocked drains, I can tell you that working on a slow drain early is always going to be better than leaving it alone. Learning how to fix a slow draining sink is an essential skill for any homeowner.
Imagine this. You're brushing your teeth and the water just sits there in the basin, rather than disappearing down the drain. Or you're doing the dishes and no matter how fast you scrub, water is just filling up higher and higher. That's your sink trying to tell you something requires attention.
The good news is that in many cases, you won't have to call a plumber for slow drains. This is a list of the most common reasons and how to solve them yourself.

Hair Build-up (Bathroom Sinks)

For a bathroom sink, hair is likely the primary suspect. I've removed some hairballs from drains that were truly of remarkable size. Not pleasant, but very common.
How to Fix It:
If you need an on-the-spot DIY solution that may or may not hold up, try straightening out a wire coat hanger and shaping a small hook at one end. Shove it down the drain, then pull out whatever comes up. Be prepared, it will smell bad.
You can buy a shower drain hair catcher for under ten bucks at Bunnings, and it's actually one of the best investments you'll ever make. So much better than trying to clear that clog later. Many people forget that the same techniques that work for a shower drain can also be applied to bathroom sinks.

Soap Scum and Sludge

Soap doesn't fully dissolve in the waste water. Then there's that fancy moisturising hand wash and body wash that leave behind a residue over time. Mixed with hair and dead skin cells, it forms a slimy clog that will put the brakes on your drain.
How to Fix It:
The bi-carb soda and vinegar method is great for bathroom sinks. Pour half a cup of bi-carb soda and half a cup of white vinegar down your drain, cover with a damp cloth for 15 minutes, then rinse away with hot water. The fizzing action makes it easier to dislodge the soapy residue. This same approach works well when learning how to fix a slow draining sink in any bathroom.
You can buy bi-carb soda and white vinegar from Coles or Woolworths for a couple of dollars.

Scrap Food, Grease (Kitchen Sinks)

Kitchen sinks have a different problem. The most obvious is food scraps, however it's the sneaky stuff which gets people. Rice absorbs water, and coffee grounds become sludgy instead of just breaking down like you might think.
Fatty residues such as cooking oils, butter can cause serious blockages. These oils congeal bit by bit as they cool, lining the inside of your pipes and catching anything else that goes down.
How to Fix It:
After you cook — whether it's a large roast or just some potatoes — run very hot water through the drain for a couple of minutes. This assists in rinsing off slight grease before it hardens.
If the grease is still there, try the hot water and dishwashing detergent method. Pour a generous squirt of detergent into the drain and then very hot (not boiling) water.

Fats and Cooking Oils

I'm putting this in its own section because it comes up so frequently. Grease and oil feel neutral when they're in liquid form, but they turn solid as soon as they cool down after being poured down your pipes. In the winter this is a big issue. The grease coats the inside of those pipes, seizes any other junk that goes down, and helps to create an ideal environment for serious blockages.
How to Fix It:
Prevention is key here. Do not pour fats and oils down the sink – wait until they solidify then scrape into a bin. But if your pan is only slick with a little bit of oil — even something as sticky and rich as duck fat — very hot water, lots of dishwashing liquid and a good scrub will do the trick.
If you suspect that the blockage is from grease or grime, you can use direct action to dilute and wash away the debris, but again: If plunging doesn't work quickly, give up. Be certain to get a seal around the drain, and push with quick, strong plunges.

Poor Drainage Fall or Damaged Pipes

The drain itself is sometimes the problem rather than what's in it. Homes settle after construction, tree roots can find their way into pipes and old plumbing eventually just gives up. If your drain has been slow all along or if sluggishness now shows up in multiple locations elsewhere in the house, you may have a bigger problem. These structural issues are often more complex than typical slower drain maintenance problems.

When to Call a Professional

This is where DIY has its limits. If these basics don't cover the problem, consider calling in a professional or reaching for the snake to clear things up. A plumber can diagnose the issue with a drain camera and work out how best to fix it.

What About Chemical Drain Cleaners?

I'm not a fan of those chemical drain cleaners they sell on TV. They're bad for your pipes (especially if you have old metal pipes), they can be hazardous to use, and often times will not actually fix the problem — at best just shifting it further into your plumbing.
I've seen broken pipes from people who use too much of that stuff. The temporary solution only costs you thousands of dollars in re-piping. It's not worth it.

Prevention Tips

And of course, an ounce of prevention is worth a pound of cure. Here's what I recommend:
For all sinks:

• Use mesh strainers and clean them
• Once a week let hot water run through the drain
• Deal with slow drains before they become clogs

For bathroom sinks:

• Less hair going down the drain
• Clean the drain stopper regularly
• In the shower, use a hair-catcher

For kitchen sinks:

• Scrape plates thoroughly before washing
• Never pour fats and oils down the drain
• Don't rinse rice and other foods down the drain

Where to Get Your Supplies

The vast majority of DIY drain fixes can be completed with simple household materials. Bi-carb soda and white vinegar is available at Coles or Woolworths. Typically, Bunnings has a decent selection for drain snakes and plungers, as well as hair catchers. If you require more specialized gear, Reece Plumbing and Tradelink have you covered.

The Reality Check

But even with good maintenance, drains can still have problems. Organic material breaks down quickly in Australia (even more so during our humid summers); thus, we end up with the occasional unexpected blockage. Tree roots are especially persistent with our natives such as eucalypts.
If your do-it-yourself efforts continue to fall short, or you're finding only temporary relief from the temptation, it's perfectly fine to call in a professional. We have the drain cameras and high-pressure water jetter to fix problems you cannot see or reach.
The trick here is do not ignore the warning signs. A sluggish drain today is often a clogged drain tomorrow … at the worst possible moment.

Final Thought

Dealing with slow drains isn't glamorous, but addressing these issues early can help you avoid more costly, frustrating problems later on. Begin with the easy fixes, know your own limits and don't be too proud to ask for help when you need it.
Ever unclogged a slow drain in the sink? What remedy helped the most? Leave a comment below and tell me what you've tried!