Try a plunger before you pour anything down a blocked drain

Water stands in the sink, or the toilet will not clear, and a plumber costs money. Two cheap fixes come to mind first: a kettle of boiling water, and baking soda with vinegar. One can damage a toilet. The other is unlikely to clear a grease clog, according to a US poison centre.

Try a plunger or a hand drain snake first, and do not pour boiling water into a toilet.

This page is for a slow or blocked sink, tub or toilet. If drain cleaner is already in the pipe, if something hard has gone down, or if sewage is coming up in more than one drain, go straight to “When to stop and call someone”.

What boiling water can damage

A toilet maker’s support page says it is not recommended to pour boiling water onto ceramic items such as toilets and bathroom vanities, because the ceramic may expand quickly and crack, which can lead to injury or a leak. Some people say the same and warn that it can damage plastic pipe as well. One person adds that it can melt the wax seal under a toilet. This page could not check that last part. One person also warns against adding hot water to a toilet that is already overflowing or badly blocked.

The pipes are a separate question. A maker of plastic (PVC) drain pipe says its pipe is for systems where the water stays at or below 140°F (60°C). Water boils at 212°F (100°C). The same maker says PVC is not a good fit where boiling water is dumped down the drain in a commercial kitchen. A home kitchen is not that, and this page cannot say how much harm one kettle does, because it depends on what your pipes are made of. If you do not know, hot water from the tap is the cautious choice.

Baking soda and vinegar

Baking soda (bicarbonate of soda in the UK) is a base and vinegar is an acid, so the two fizz and give off carbon dioxide gas. The National Capital Poison Center says drains are not airtight, so the gas escapes instead of building enough pressure to push a clog out, and that the mix is unlikely to be strong enough to melt a tough oil or grease clog.

People split on it. Some people say it is a cheap, non-corrosive cleaner. Others say it cannot clear a clog and only cancels itself out. One person says to pour the two in one after the other, not mixed first. Another says the fizz stirs a clog loose so hot water can wash it away, but that the two are too weak to dissolve it. Some people point out that the mix does not dissolve hair, and one person that soap does not either: hair has to be pulled out.

Baking soda is not caustic soda. Some people point out that baking soda and vinegar are safe on skin, and that the burn stories come from mixing baking soda up with caustic soda, also called lye (sodium hydroxide), which is a different and dangerous chemical. The National Capital Poison Center lists sodium and potassium hydroxide among the common ingredients of drain cleaners.

What people use instead

Many people say a hand drain snake does better than a chemical cleaner on a clog made of hair or something solid, and costs far less than a plumber. A drain snake is a long, thin, bendy rod or plastic strip that you push into the drain to hook the clog or break it up, then pull it out. One person says a toilet auger, which is a snake made for toilets, is easier than household remedies for a stubborn blockage.

Some people say a plunger is the first thing to try, and that how you use it matters: it has to make suction, not just push.

For the curved pipe under a sink, one person says it can be taken apart and emptied, and that a blockage deeper in the wall or floor is a job for a professional. One person says hair gathers on the stopper in a bathroom sink, so the stopper may have to come out. One person says a hard object, such as a plastic fork, will not move with soap or other household remedies and has to be physically removed.

For a greasy kitchen drain, some people pour in dish soap and follow it with hot water, saying soap breaks grease down.

If you use a chemical drain cleaner

Some people prefer a strong chemical cleaner when other methods have failed, even though it costs more. One person warns that a drain cleaner needs gloves; another, that it can destroy plumbing quickly if misused. The National Capital Poison Center says some are strong acids and some strong alkalis, that caustic products burn on contact with skin, eyes and the gut, and that the injury cannot be reversed, only treated. It says to buy one only if nothing else will do the job.

Its rules, in short:

• Read the label first, and follow it exactly.
• Never mix household cleaning products. It can make poisonous fumes.
• Wear goggles and rubber gloves, and open a window if the label says to.
• Pour it carefully and close to the drain. It can splash back if it is poured from too high or if too much goes into a completely blocked drain.
• Keep it in its own container with the child-resistant cap on, and never move it into a food or drink container.
• Do not use it when children or pets are around.

If cleaner is already standing in a drain, one person says not to plunge it, because you would be plunging the cleaner. This page cannot give a safe way to clear a drain with cleaner in it. A plumber can.

Stop it coming back

Thames Water, a UK water company, says even small amounts of cooking fat, oil and grease can build up in pipes and harden when cold. It says to let grease cool and scrape it into the bin, and to pour used cooking oil into a sealable jar or bottle and put that in the bin. Some people say the same. One person suggests catching grease in foil or paper towel and throwing that away. Some people use a hair catcher over a shower or tub drain, so hair never reaches the pipe. One person points out that a garbage disposal does not turn solids into liquid.

When to stop and call someone

Some people say do-it-yourself methods cannot fix a main sewer line that tree roots have entered, or a collapsed pipe: those need a plumber.

Yorkshire Water, which serves Yorkshire in England, suggests that for a toilet or sink on the ground floor or in a basement you check whether other drains in the home are slow too. If your neighbours are affected as well, it says the problem is likely a drain that belongs to the water company. It also says that in a rented home you should tell your landlord, and that if you own the home you should contact your insurance company before you look for a drainage contractor, because not telling them could affect a later claim.

Who this page is not for

It is not for a blocked drain with cleaner already in it, a hard object stuck in a toilet, sewage coming up in more than one drain, or a blockage that keeps coming back. Those need more than a plunger or a snake. If you rent, tell your landlord first.