Plumbing pros warn why you should never pour boiling water down the drain – and what to do instead

We've all done it before, whether cooking or unclogging pipes, but the answer to 'can I pour boiling water down my drain' is a resounding no. But why, exactly?

As our experts explain, doing so isn't just dangerous with risks of splashes and scalding, but may actually cause irreparable damage to your plumbing and pipes.

Here, they share why boiling water is a liquid to never pour down your sink, with advice on what to do instead, whether you have a stubborn blockage, frozen pipe, or simply want to keep your drains maintained.

Why you should never pour boiling water down the drain

You may already know how to dispose of cooking oil without pouring it down your drain to prevent clogs, but it's just as important to never pour boiling water down, either, particularly when addressing any reasons your sink won't drain or when working to fix a clogged kitchen sink.

As Aaron Adams, master Plumber and CEO of Aaron Services: Plumbing, Heating, Cooling, explains, 'The main reason you shouldn't put boiling water down your drains is that oftentimes drain pipes aren't designed to handle hot temperatures. Pipes that bring water to your faucets are often made of different materials than pipes that take the water away.'

For example, Aaron highlights, pipes that take hot water to your faucets are generally made of more modern pipe types, like CPVC (chlorinated polyvinyl chloride), which are tested and rated to carry hot water to your faucets and showerheads safely. On the other hand, most drain pipes are made of PVC, and this type of pipe is not rated to handle boiling water.

'Even the hot water that modern water supply lines are designed to carry isn't meant to be as hot as boiling water,' he continues. 'For example, CPVC is generally designed to handle water as hot as 200° Fahrenheit, while PVC can only handle temperatures of up to 140° F. Water's boiling point is 212° F.

'While the water that goes down your kitchen sink drain can be hot to help flush away residual grease, for example, it's less than boiling, and starts dropping in temperature as soon as it leaves the heat source that is your water heater.'

So what happens when you pour boiling water down a drain?

'It can cause the pipe to slightly melt or soften, which can destroy the integrity of the pipe,' warns Aaron. 'This shifting can cause pipes to disconnect at fittings or sag.

'Drain lines are designed to work with gravity to properly drain, so when they sag, the angle that the lines are designed to drain at can be compromised.

'In short, you can get little dips or "bellies" in your drain line where waste and debris accumulate and eventually clog the pipe.'

Additionally, this can particularly pose issues when trying to thaw frozen pipes and avoid burst pipes, as the sudden increase in temperature can cause damage to the drain.

In fact, says Aaron, 'The extreme temperature change can cause more problems than you started with!'

What to do instead

Before you can work out the alternative solution most suited to you, ask yourself: why are you pouring boiling water down your drain in the first place?

If you have a clogged drain, and are seeking DIY drain cleaning solutions professionals swear by, instead of reaching for the kettle, 'Start with a drain weasel or hand auger [available at Amazon] to clear the line,' recommends Aaron. 'You can also carefully try a drain cleaner like Liquid Plumr, available at Walmart. If those DIY efforts don't help, call in the pros.'

Importantly, you should never be tempted to use baking soda and vinegar to unclog a drain, warn experts, as, like boiling water, this can do more harm than good.

Like most things, prevention is better than cure – investing in simple drain covers, such as the OXO Good Grips Silicone Sink Drain Strainer available at Walmart, can go a long way in stopping the occurrence of clogs.

If you're trying to keep your drains maintained, Aaron suggests regularly running hot water from your faucets down the drains and purchasing a drain maintenance cleaner such as Endure from a local plumber.

'These products are designed to regularly go down the drain to avoid build up,' he says. 'You should also just generally be careful with what you put down your drains, and avoid fats, oils, grease, and solids to keep your drains healthy.'

Finally, if it's frozen drain pipes you're dealing with, Aaron advises that you should slowly thaw the pipe out with a hair dryer or space heater, such as the Mainstays Ceramic Fan-Force Electric Space Heater available at Walmart.

'You should be careful, though, as you may have pressurized pipes that have also frozen,' he adds. 'You don't want to thaw out pipes if anything has cracked.'

If you're concerned about this, it's always safer to call a professional plumber for help or advice.

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Meet our expert

Aaron Adams

Atlanta's award-winning service provider Aaron Services boasts a host of five-star online reviews, with trusted and skilled technicians who specialize in all things HVAC and plumbing.

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