Does Drano Really Work? And How Does it Work?

Drano is probably the most popular chemical drain cleaner in the market. There is however all manner of information regarding it on the internet, some good and some bad.

So, should you use Drano to clear drain clogs? And how does Drano work in clearing clogs? Better still, why do plumbers hate Drano?


By the end of this post, I hope to explain to you everything that you need to know about Drano.

Drano, whose active ingredient is sodium hydroxide (lye/caustic), works through a chemical reaction which releases a lot of heat. The heat breaks down the clog while the lye also reacts with grease to form a soapy substance which dissolves the clog material.

I often have people ask me “Does Drano work”?

Drano works and is actually very effective in clearing clogs in kitchen sink, bathroom sink and shower/bathtub drains. However, Drano will only clear light organic clogs (soap scum, grease, hair, food waste). Solid clogs will need powerful tools and/or the intervention of professionals.

The main reason plumbers hate Drano is due to its corrosive nature. When Drano sits in the pipes for long, it will soften PVC pipes, weaken steel pipes, eat away the glue that bind pipes together and may even crack toilets. Drano will also burn your skin, irritate the eyes or even hurt your lungs.

If Drano doesn’t unclog a drain, you will be left with a toxic solution which must be drained before trying other unclogging methods. You can either wait for the fixture to drain slowly, or drain it out yourself then pour a cup of baking soda and another cup of vinegar then wait for 15 minutes.

If Drano fails to unclog a drain, it can actually make the clog worse. The solution solidifies farther down the drain line resulting in an even worse clog.

You should not use Drano if you have multiple clogged drains, you have had persisted clogs, you are on a septic system or you have old pipes. Drano should especially not be used to unclog toilets since the heat produced can crack the bowl.

How it Works


To understand how Drano works, you first need to understand what it is made of. So, what is inside a bottle of Drano drain cleaner?

As I have already mentioned, the main and active ingredient in Drano is sodium hydroxide which is commonly known as lye or caustic soda. It also contains other ingredients like aluminum, salts, bleach and water.

When you pour Drano inside a drain, a series of chemical reactions takes place. The first reaction is the break down or decomposition of organic matter by the sodium hydroxide.

Secondly, sodium hydroxide reacts with the aluminum in an exothermic reaction. An exothermic reaction is a reaction that emits/releases heat to the surrounding.

This heats speeds up the decomposition of the organic matter by further melting the clog. You see when for example your bathroom sink or shower is clogged, what you have is a ball made of hair, soap scum, oils and shampoo which form the clog.

Of course if you introduce heat into the clog you will be in a position to break it down faster. That is what this second reaction does.

After that, the sodium hydroxide also reacts with the grease to form a soapy substance. This soapy substance dissolves the clog matter which makes it easy for it to be flushed down the drain by hot water.

The whole process takes between 15 and 30 minutes depending on the severity of the clog. As I have already mentioned, there is usually no guarantee that Drano will clear your clogged drain.

So, how should you use Drano to unclog drains?

How to Use It


This is how to use Drano to clear drain clogs according to SC Johnson, the company that manufactures it:

  • Drain the standing water. With a clogged drain, you will either have a partial or full clog. With a partial clog, the fixture will drain slowly but if you have a full clog you will have standing water in the fixture. Start by draining all the standing water. You want the Drano to work directly on the clog.
  • Pour the Drano inside the drain. The amount to use depends on the severity of the clog. If you have a slow draining fixture, use half of the bottle (32 oz. size). On the other hand, if you have a nasty clog, empty the entire bottle down the drain.
  • Allow the Drano to work out its magic for 15 minutes if you had a slow draining fixture. However, if you had a terrible clog wait for 30 minutes.
  • Flush the drain with hot water and check if the Drano worked.
  • If the clog is still there, you can repeat the above steps or explore other drain clearing methods.

Does It Really Work?

So, does Drano really work? Is it worth your money and time?

The simple answer is Yes. Drano works and it actually works most of the time. It is especially successfully in clearing clogs in kitchen sink, bathroom sink, bathtub and shower drains.

That is because most of the waste that goes down through these drains is organic. As we already have seen, Drano is quite effective in breaking down organic waste.

Of course there are times when Drano will not work. All clogs are not created equal. This is especially the case when you have old problematic pipes.

Let us now look at instances where Drano does not work, or when you shouldn’t use Drano to try and unclog Drains.

When Should You Not Use Drano

If you have more than one clogged drain, using Drano is not a good idea. Drano works best if the clog is only affecting one drain? Why is that though?

Your house’s plumbing is one network of pipes referred to as the drain-waste-vent system. All the different drain lines (sinks, showers, tubs, toilets, washers) are connected together and leave the house through the lateral sewer line in your yard.

The lateral sewer line is then connected to the municipal sewer line or septic tank. If you didn’t already, your kitchen sink and toilet drain use the same sewer line and may “communicate” in case of a clog.

Now, if you have 2 or more clogged or backing up drains, it means that the clog is affecting the main house drain line far from the fixtures.

As such, the entire drain lines are full of water or raw sewage which makes using Drano a bad idea. The Drano won’t even get to the actual clog.

Another thing you need to know is that you fixtures could be draining slowly not because you have a clog in your drain lines but because the plumbing vent is clogged.

A plumbing vent is the vertical pipe which runs through the roof of the house and is usually connected to the main house drain stack.

The vent allows air into the draining system allowing the fixtures drain fast, and also allows sewer gases to exit the system. When it is clogged, you will end up with gurgling and slow draining fixtures.

You should also not use Drano if you are having repeated clogs. When a certain fixture keeps on clogging and there is nothing wrong you are doing to cause the clog, there is a deeper problem which needs to be examined by a professional.

Also, if you have tried using Drano to clear a clog unsuccessfully, I wouldn’t recommend pouring more Drano down the drain. Since you don’t know what exactly the clog is, you better contact a licensed plumber to come have a look.

And finally, I would advise against using Drano if you are on a septic system. A septic system depends on bacteria inside the septic tank to break down the waste whereby the sludge settles at the bottom of the tank while the clear water flows out to the leach field.

If you introduce Drano in the septic tank, it will kill these bacteria meaning there will be no way for the organic waste to be broken down.

The effects of that are that you will have raw sewage backing up to the house and/or a clogged leach filed. Fixing any or both of these issues is extremely expensive.

Why Do Plumbers Hate It?

There is no plumber who will recommend Drano to you. Why is that the case though?

Are plumbers just jealous because Drano denies them lucrative working opportunities? I mean it is way cheaper to buy a bottle of Drano than have a plumber come over simply because your bathroom sink won’t drain.

The main argument or concern plumbers put forward against Drano is its effects on plumbing pipes. This is regardless of whether you have steel pipes or PVC pipes.

According to plumbers, the heat produced by Drano during the decomposition of the clog is bad news for your pipes. It will soften PVC pipes and weaken steel pipes ultimately resulting in leaks.

Drano will also eat away the glue used to stick pipes together, again resulting in leaks. Is that the truth though? It depends on who you are asking.

According to SC Johnson, Drano will not harm your plumbing in any way. They say it is something they have even tested.

Plumbers argue that Drano and other chemical drain cleaners are tested under ideal conditions and over a short period of time. Effects of Drano apparently take a long time to manifest themselves.

They say that Drano will not affect new pipes the same way it does old ones, and over a long duration of time. Drano is tested on new pipes and probably over a short period of time.

I cannot accuse the plumbers of dishonesty since they spend most of their time checking out pipes. They could actually be right.

What I would recommend is not using Drano if your house has old pipes. It is better to be safe than sorry. Needless to say.

 What you should however know is that Drano can burn your skin and irritate your eyes when it comes into contact with them or could even make you blind. It is especially dangerous and could be fatal when ingested by children.

What Happens if It Doesn’t Work?

If you have a clogged drain and you decide to hire a plumber, the first question they will ask when they get to your house is “Have you tried Drano on it”?

Do you know why they ask that? Because Drano is toxic and therefore dangerous to their health and could damage some of the tool they use to clear clogs.

Most plumbers will actually leave your house and only come back after 24 hours when the conditions are safe to work in.

You see, if you have Drano sitting in your drain and you try plunging or snaking, there is every chance that the Drano will splash on your skin and cause serious burns or even irritate your eyes. Drano can actually make you blind.

Attempting to use other chemical drain cleaners will result in other reactions with production of toxic fumes which can hurt your lungs.

Actually, this is another reason why plumbers don’t recommend Drano. If it fails to work it leaves you in a big problem.

What you can do is wear elbow-length nylon gloves and drain the solution from your fixture and dump it appropriately. You can afterwards use baking soda and vinegar to try and clear the clog.

Can It Make a Clog Worse?

Believe it or not, Drano can actually make a clog worse that it was before. Another point to validate plumbers’ dislike for Drano!

If you have a nasty clog, Drano will first decompose the clog after coming into contact with it. That will turn the clog into a solution which should easily wash down the drain.

However, the solution can solidify farther down the drain line resulting in an even worse clog. That is why I recommend using Drano only once but if the clog persists contact a plumber to have a look.

Does It Work in Standing Water?


According to the manufacturer SC Johnson, Drano works perfect even in standing water. They say that “It pours straight through the water and attacks the clog directly”.

While I am not disputing that, I have found out that Drano and basically other drain cleaners work best when you first drain the water.

If you however don’t feel like draining a bathtub full of water, go ahead and do what they recommend. I should warn you that if the Drano fails to work you will be left with a tub full of toxic water to drain.

Does It Work in Toilets?

One place you should not use Drano to clear clogs is the toilet. A toilet is designed a little different than other fixtures.

As you already know, there is water at the bottom of the bowl at all times. That is made possible by the S-shaped trap.

The water prevents sewer gases from coming up to the bathroom. Although all drains have a trap, a toilet’s trap is integrated with the toilet, which is made of china and that is where the problem is.

When china is heated, it expands and cracks. And as I have already said, pouring Drano in a drain results in a reaction which releases lots of heat.

The heat is enough to crack a toilet bowl. A toilet bowl cannot be repaired and will need to be replaced. That is another reason why plumbers don’t recommend Drano.

How Does It Work on Hair


Drano is actually very effective in clearing clogs caused by hair. Hair is usually responsible for most of the clogs in shower, bathtub and bathroom sink drains.

It combines with soap scum, oils and shampoo to form a ball which clogs the drain line especially around the P-trap.

Drano decomposes organic waste fair fast and hair being an organic substance is no exception. If you therefore have a clog in you shower drain then Drano will most likely clear it.

What is better a better alternative?

So, what if you don’t want to use Drano, what should you use? I have found out that a combination of baking soda, vinegar and boiling water is every effective in clearing clogs yet it is so safe.

Just pour a cup of baking soda down the drain followed by another cup of vinegar and after 15 minutes blast boiling water down the drain.

And basically that is pretty much everything about Drano. I hope this guide was helpful.

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