Chemical drain cleaning: what works and what to skip

Chemical drain cleaners are strong products that dissolve hair, grease and soap, and they sometimes clear a local clog in a sink or tub. They do not clear roots, collapsed pipe or a blocked main line, and a failed attempt leaves standing water that is dangerous for the next person to work on. A plunger, a hand auger or a service visit is usually a better first move. Below is what the products are, what the common kitchen fixes do, and when to stop.

Do chemical drain cleaners work?

Sometimes. Lye based and acid based openers can dissolve organic matter such as hair and grease in a short, slow draining line, and enzyme products work slowly on soft buildup. They do poorly on solid objects, roots and a long run where the product dilutes before it reaches the clog. If it fails, a plunger or a cable is the next step.

Wikipedia's entry on the drain cleaner groups them into caustic, acidic and enzymatic types. Caustic ones use sodium hydroxide, also called lye, and generate heat as they react. Acid types act faster and are more hazardous.

Products that claim to be gentler are not automatically weak. Read the label for the active ingredient and the warnings, not the front of the bottle.

Which chemical is used for cleaning drainage?

The three main kinds are caustic, acid and enzyme or bacterial products. Caustic openers use sodium hydroxide or potassium hydroxide. Acid openers use sulfuric acid and are usually sold to trades. Enzyme products use bacteria or enzymes that digest organic matter over hours. Which one suits you depends on the clog, the pipe and your tolerance for risk.

If you are choosing between brands, our page on the best chemical to unclog a sewer line compares what is sold for main lines.

Is it safe to use drain cleaner in my pipes?

It can be, if you follow the label exactly, and it is risky if you do not. Never mix two products, or a product and bleach or vinegar. Mixing cleaning products can give off poisonous fumes, so follow each label and never combine them. If the first product fails, do not add a second.

Practical rules:

• Wear eye protection and gloves, and ventilate the room.
• Do not use any chemical in a toilet bowl that is full of water or in a fully blocked drain: it sits there and can splash.
• Keep a plunger away from a drain with chemical in it, because it can splash back at you.
• Tell anyone who works on the drain later that you used a product, so they can protect themselves.
• Keep drain cleaners locked away from children and pets.

If someone swallows a product or gets it in the eyes, call Poison Control at 1-800-222-1222, or 911 in an emergency. Unused product goes to household hazardous waste collection, not down the drain or in the trash. Check the city or county program for locations.

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Can salt be used to unclog a drain?

Salt alone barely helps. Poured down with hot water, it may loosen a light grease film because the grains scrub a little and the water melts fat, but it does not dissolve hair or a solid plug. It is cheap and low risk for sinks, so it is a fair first try on a slow drain, not a fix for a stopped one.

If the drain is fully stopped, move to a plunger or a hand auger. A cup of salt followed by a kettle of very hot water is the strongest version, and it should be tested on a slow drain, not a dead one. Our clogged drain home remedy page puts the homemade methods side by side.

Does Dawn dish soap unclog drains?

It can help with grease. Dish soap breaks up fat, so a squirt followed by hot water can free a greasy kitchen line. It does not dissolve hair or a solid object. Dish soap also does not cause clogs in normal amounts, though the grease that rides along with dishwater is what builds up over time.

Use a generous squirt, wait a few minutes, then flush with a kettle of hot water and test the flow. If it is still slow, it is not a grease clog, and a plunger or cable is the next step.

Does boiling water or hot water help a clogged drain?

Hot water helps with grease in metal pipes and sinks, but it is a poor tool for other clogs and can damage some fixtures. Boiling water can crack a porcelain toilet bowl or sink and soften plastic fittings or the joints on PVC pipe. Very hot tap water is the safer choice, and a kettle just off the boil is a compromise in a metal pipe.

In a toilet, pouring hot water in rarely clears a clog and may crack the bowl, so use a plunger first. Hot water does make a better follow-up after soap or a cable, because it flushes loosened grease away.

What will dissolve hair in a shower drain?

Hair mostly needs to be pulled out, not dissolved. A plastic drain snake with barbs, or a hair catcher cleaned weekly, handles most of it. Caustic cleaners will dissolve hair, but they are the harshest option for a small clog you can reach by hand.

Start with a plunger or a barbed strip, and read cleaning hair from a drain for step by step methods. If you must use a product, choose one labeled for hair and follow the label. A visit makes sense when several drains are slow, because that points beyond hair.

When should I stop and call someone?

Stop when more than one drain is slow, when water backs up in the lowest fixture, when you smell sewage, or when a product has failed. All of those point beyond a local clog. A service visit with a cable or a camera is faster and often cheaper than a second bottle, and it keeps you away from a pool of chemical.

For a stopped main line or repeated slow drains, see drain snaking and our quote page. Snaking by a plumber runs roughly $100 to $300 for a fixture drain in national guides, and a hand auger costs about $10 to $30 to buy. West Coast prices are often higher, and the written quote after a visit is the real price. The LA Drain Works home page lists the other services.

Questions people ask

Do chemical drain cleaners damage pipes?

Some can. Strong acid and some caustic products can attack old metal or soften plastic if they sit in the pipe. Heat from a lye reaction is hard on a stalled drain. Repeated use is more risky than a single careful one. Check the label for your pipe material.

Is Dawn dish soap good for clogged drains?

It is good for grease clogs and poor for hair or objects. Use it for a greasy kitchen sink along with hot water. Dish soap does not cause clogs in normal use, so there is little risk in trying it first.

Can I use drain cleaner with a plunger?

Not safely. A plunger can splash a caustic product onto your face and hands. If you have poured product in, wait for the label's time, flush with water, then use a plunger only if the water is clear. Do not use a plunger if you suspect the product is still in the bowl.

Do chemical drain cleaners work on a main sewer line?

Rarely. A main line clog is usually roots, grease or collapsed pipe a long way from the drain, and the product dilutes before reaching it. A cable, a jetter or a camera visit is the usual answer. See cleaning out a main sewer line.

Can I mix vinegar and baking soda with a chemical cleaner?

No. Never mix household chemicals unless the label says so. Vinegar is an acid and can react with caustic products and with bleach. If the first product failed, stop and call a professional rather than adding another.