Buy ComStar Pure Lye: 99.9% lye beads with the fullest directions, including a mix for a fully stopped drain. Pick Instant Power for a tub or shower, Roebic if you want a cold-water method, or Drano Granules for kitchen grease. Never use lye after acid or bleach.
Top pick: ComStar Pure Lye$19.99 at AmazonPrice as of Oct 24, 2026, 5:30 AM EDT
Each one is the genuine brand, new and in stock on Amazon when we checked just after midnight on Oct 22, 2026, and each scored 7.0 or higher on our spec score.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.
How the four compare on our spec score
Five checks from each maker’s own pages and safety sheets, equal weight. The rules and every input are in the method section near the end.
PlumbingPicks spec score out of 10, from ComStar’s, Instant Power’s, Roebic’s and SC Johnson’s product pages and safety sheets, read Oct 21 and 22, 2026. It is not a customer rating.
ComStar and Instant Power are close. ComStar wins on directions, with a separate method for a drain that won’t move at all. Instant Power wins on pipe guidance, naming more metals and surfaces to keep it off.
Roebic lost points because it names only the kitchen sink and lists pipes to avoid without saying which are safe. Drano lost points for a 60 to 100% lye range on its sheet and a kitchen-only use list.
Each pick, in detail
What each bottle is for, the dose and the wait, and where its maker says not to use it.
99.9% lye beads1 lb or 2 lbItem 30-5003 heaping tbsp per slow drain1 cup per quart for a full clogpH 14 (5% solution)
Buy it if
A drain is fully stopped, or you keep a grease trap or septic tank and want one bottle with a dose for each job.
Skip it if
Acid, bleach or another drain cleaner is already in the line, or the drain has aluminum parts the beads would touch.
ComStar Pure Lye is the crystal opener I’d keep under the sink, and I’ve used it. It’s sodium hydroxide beads, 99.9% on ComStar’s safety sheet revised December 12, 2022, and the front label says 99% pure. ComStar International, the maker, was the Amazon seller when we checked.
What puts it on top is the directions. For a slow drain with grease, hair, soap scum or oil, ComStar says to run hot water for a minute to warm the pipes, add 3 heaping tablespoons (about ¼ cup, 2 oz), wait 15 minutes or longer, then run hot water until it dissolves.
For a drain that’s fully stopped, ComStar gives a second method. Stir 1 cup of beads into 1 quart of cold water in a plastic pail, using a non-metal stirrer, pour the mix into the drain, and leave it overnight if you can. None of the other three bottles gives a separate method for a drain that won’t move.
ComStar names more places than anyone else here: slow drains, grease traps at 2 lb per 100 gallons, septic tanks at 6 lb a year for a 500 gallon tank, and basement floor drains.
Its question page says it’s safe in garbage disposals with about a 20 minute stand. ComStar also says the beads sink through standing water to reach the clog.
There are limits. ComStar says to keep it off aluminum, floors and paint, and not to use it if any other chemical has been used. It isn’t allowed in septic tanks in Massachusetts. The safety sheet calls for a face shield, gloves and an apron.
My call: buy the 1 lb for a house and the 2 lb if you run a grease trap. Put a dish pan over the drain after you pour, as ComStar says, and stand back. ComStar gives no repeat limit, so I’d try once more at most and then call a plumber.
Maker posts a child-resistant packaging certificate
Cons
Not for toilets, urinals, dishwashers or disposals
Keep off aluminum, brass, chrome and fiberglass
No method for a fully stopped drain
Safety sheet dates from 2020
100% lye crystals1 lb bottleItem 16501 heaping tbsp + 1 cup hot water15 to 30 min waitpH 13 to 14
Buy it if
A bathroom sink, tub or shower drains slowly from hair and soap scum, and you want a small, measured dose.
Skip it if
It’s a toilet or a garbage disposal. Instant Power rules both out.
Instant Power Crystal Lye Drain Opener is the bottle I’d reach for on a slow tub or shower, and I’ve used it. It’s item 1650 from Instant Power Corporation of Dallas, 100% sodium hydroxide on its safety sheet, and Amazon itself was the seller when we checked.
The dose is small. Take out as much standing water as you can, make sure the water in the drain is cool, and pull the strainer if it comes out. Pour 1 heaping tablespoon slowly into the drain.
Then add 1 cup of hot water and cover the opening with a bowl right away. Don’t seal it, since pressure can build.
Leave it 15 to 30 minutes, then flush with hot water. If it’s still slow, repeat once. Instant Power says that if two treatments don’t clear it, call a plumber and tell them you used crystal lye. That stop rule is why it scored 9 on directions.
It scored a full 10 on pipe guidance. Instant Power says it’s safe for all pipes and septic systems, then names what to keep it off: fixtures and utensils made of aluminum, brass, chrome, wood, paint, acrylic or fiberglass. That matters on a tub, where the overflow plate and drain flange are often chrome or brass.
Its use list is narrower than ComStar’s: kitchen and bathroom sinks, tubs and showers. It’s not for toilet bowls, urinals, dishwashers or garbage disposals, and it’s never to be used with a plunger, ammonia, acid, bleach or another drain opener.
Instant Power posts a certificate of compliance listing item 1650 under the Poison Prevention Packaging Act, the federal child-resistant packaging rule. Many lye recalls in the CPSC record were for packaging that failed that rule, so it’s worth knowing. My call: wipe any crystal off the chrome right away and keep the bottle locked up.
96 to 100% lye2 lb bottleModel HD-CRY-DO1 tbsp + 2 cups cold water15 min waitpH over 12.5
Buy it if
A sink is slow with grease, the pipes are PVC or copper, and you’d rather keep the heat down with cold water.
Skip it if
The house has galvanized steel or lead drain pipe, or the clog is in a toilet or disposal.
Roebic Heavy Duty Crystal Drain Opener is the one I’d pick for a cooler, slower job, and I’ve used it. Roebic Laboratories calls it professional strength, 100% lye on the label, and its safety sheet revised March 4, 2022 lists 96 to 100% sodium hydroxide. Amazon was the seller when we checked, in a 2 lb bottle.
Roebic does one thing differently: cold water. Its directions say to apply with cold water to minimize heat. Take the standing water out of the sink, pour 1 tablespoon into the drain, then pour 2 cups of cold water and cover the drain with a plastic bowl. After 15 minutes, flush slowly with cold water for 30 seconds.
Lye gives off heat when it meets water; ComStar’s sheet calls it exothermically soluble. Every maker here manages that heat. Roebic does it with cold water, the others with a cover over the drain and limits on boiling water. Our hot or cold water table below lays the four side by side.
Roebic is the most specific about pipes to avoid. Its label says no aluminum, lead, zinc or galvanized pipe, which rules out many older homes with galvanized steel drains. It doesn’t say which pipes are safe, though, so it scored 7 on pipe guidance.
Its directions name only the sink, and the label rules out toilets and garbage disposals. Roebic’s directions say to repeat if needed but give no limit, so it scored 8 on directions. Don’t use any other drain cleaner with it, including acids or ammonia, as splashing or hazardous gases may result.
My call: Roebic is a good fit for a slow kitchen or bathroom sink on PVC or copper. If you don’t know what your drain pipe is, look under the sink first. Gray or silver threaded pipe with rust at the joints is often galvanized steel, and Roebic rules that out.
Sodium hydroxide 60 to 100%Sodium chloride 10 to 30%8.8 oz boxModel 6990273 heaping tbsp + 2 cups hot water15 min wait
Buy it if
The kitchen sink is slow with cooking grease, there’s no garbage disposal, and you want a measured, familiar box.
Skip it if
The sink has a disposal, or the clog is in a tub, shower or toilet. SC Johnson rules out all four.
Drano Kitchen Granules is the lye opener most people already know, and I’ve used it. SC Johnson says it’s best on grease clogs, with a formula that heats the water to melt them. Amazon was the seller when we checked, in the 8.8 oz box, model 699027.
It isn’t pure lye. SC Johnson’s safety sheet, revised July 11, 2025, lists 60 to 100% sodium hydroxide and 10 to 30% sodium chloride, and its ingredient page adds sodium stearate as a wetting agent. That range is why it scored 7 on lye strength, against 9 or 10 for the others.
The directions are clear. Sponge out the standing water, pull the strainer if you can, pour 3 heaping tablespoons into the drain, then 2 cups of hot water that isn’t boiling. Wait 15 minutes and flush with cold water. If it’s still clogged after a second try, SC Johnson says to call a plumber.
SC Johnson is firm about the dose. Its precautions say not to exceed it, because too much can cause stagnation or permanent pipe clogging. It also says not to pour it into standing water or cold water, so get the water out of the sink first.
The use list is the shortest here. It’s for the kitchen drain only, with no bath, shower or toilet, and not for a sink with a garbage disposal. SC Johnson points disposal owners to Drano Max Gel instead. Keep the granules off aluminum, stainless steel, wood, paint, acrylic and fiberglass, which matters on a stainless kitchen sink.
SC Johnson says it’s safe on PVC and metal pipes and on septic tanks. My call: Drano Granules is fine for a slow kitchen sink with no disposal. Wipe any granules off the stainless sink right away. For a bathroom drain, buy Instant Power or ComStar, whose labels allow it.
The four side by side
Tap a column heading on a computer to sort by spec score or strength.
From each maker’s product page, directions and safety sheet, read Oct 21 and 22, 2026. Sizes and sellers from Amazon’s product data, Oct 22, 2026.
Read the toilet and disposal columns first. Three of the four rule out both, so a stopped toilet isn’t a job for crystals; our best toilet auger page covers the tool that is. ComStar is the only one whose maker allows a garbage disposal.
Is lye a good drain cleaner?
For the clogs the makers name, yes. Here’s what crystal lye is good at, and where it fails.
Good at: grease, hair and soap scum
Instant Power says its crystals melt and dissolve grease, hair, soap and scum. ComStar adds oils, and SC Johnson says its granules are best on grease clogs.
Good at: monthly upkeep
ComStar recommends ¼ cup a month to keep a drain running free. That’s a dose for a drain that still moves, not a cure for one that’s stopped.
Bad at: paper, plastic and metal objects
SC Johnson says not to use its granules if the clog is paper, plastic or metal. A dropped cap or a wad of wipes has to come out with a tool.
Risky with: aluminum and the wrong pipe
Instant Power’s sheet says lye meets aluminum, tin and zinc and makes flammable hydrogen gas. Roebic rules out aluminum, lead, zinc and galvanized pipe.
So crystal lye fits the slow sink or tub, not every clog. My call: plunge first, then try a hand auger, and use a crystal opener when the clog is grease or hair. If you’re deciding between a tool and a bottle, our drain snake vs drain cleaner vs plunger page walks through that order.
A hair clog in a bathroom pop-up often comes out faster with a plastic hair wand than with any chemical. Our best drain cleaner for hair page compares both.
How much crystal lye to pour, maker by maker
The four makers’ doses run from 1 tablespoon to a full cup. Here they are as one chart, with the water each one adds.
From ComStar’s, Instant Power’s, Roebic’s and SC Johnson’s directions, read Oct 21 and 22, 2026. A heaping tablespoon is drawn a little longer than a level one.
Step
ComStar
Instant Power
Roebic
Drano Granules
Before pouring
Run hot water a minute to warm the pipes
Remove standing water; water in the drain cool; pull the strainer
Remove standing water
Sponge out standing water; pull the strainer
Dose
3 heaping tbsp (¼ cup)
1 heaping tbsp
1 tbsp
3 heaping tbsp
Water after the dose
Hot water after the wait
1 cup hot water
2 cups cold water
2 cups hot, not boiling
Cover the drain
Dish pan or deep metal container
Bowl, not sealed
Plastic bowl
Not stated
Wait
15 minutes or longer
15 to 30 minutes
15 minutes
15 minutes
Then
Hot water until dissolved
Flush with hot water
Cold water, slowly, 30 seconds
Flush with cold water
If it’s still slow
Not stated
Repeat once; then a plumber
Repeat if necessary
Repeat once; then a plumber
From each maker’s directions, read Oct 21 and 22, 2026. “Not stated” means we didn’t find it in the maker’s text.
More isn’t better with lye. SC Johnson warns that going over the dose can cause stagnation or permanent pipe clogging. My call: measure with a plastic spoon you keep with the bottle, not a kitchen spoon, and never shake crystals straight from the bottle into the drain.
Hot or cold water with lye? The makers disagree
Every lye label talks about water temperature, and they don’t say the same thing. Here’s each maker’s rule and its reason.
Maker
Water rule
Why, in the maker’s words
Roebic
Cold water with the dose and for the flush
“Apply with cold water to minimize heat”
Instant Power
Cool water in the drain, then 1 cup of hot water
Crystals create heat to melt grease; cover so it can’t splash back
Drano Granules
2 cups hot, not boiling; never into standing or cold water
Formula heats water to melt grease
ComStar, slow drain
Hot water first to warm the pipes, hot water after
To dissolve the beads
ComStar, stopped drain
Mix 1 cup into 1 quart of cold water in a plastic pail
Dissolve before it goes in; leave overnight
From each maker’s directions and product page, read Oct 21 and 22, 2026. ComStar’s safety sheet lists sodium hydroxide as exothermically soluble in water, meaning it gives off heat as it dissolves.
The heat is the point and the danger. Lye warms the water it dissolves in, which helps melt grease, and every maker caps it a different way. Nobody here says to use boiling water.
My call: follow the label on the bottle you bought, not a neighbor’s tip. If you switch brands partway through a clog, wait for the first dose to clear and flush with plenty of water before the second brand goes in.
Is lye safe for PVC, toilets and disposals?
Forum threads argue about this. Here’s what the four makers actually say, pipe by pipe and fixture by fixture.
Pipe or fixture
ComStar
Instant Power
Roebic
Drano Granules
PVC
Safe on plastic pipe
Safe for all pipes
Not stated
Safe on PVC
Copper and other metal pipe
Safe on metal pipe
Safe for all pipes
Not stated
Safe on metal pipes
Aluminum, lead, zinc, galvanized pipe
Keep off aluminum
Keep off aluminum fixtures
Do not use
Keep off aluminum
Chrome or brass fixtures
Safe on chrome trim
Keep off
Not stated
Not stated
Stainless steel sinks
Not stated
Not stated
Not stated
Keep off
Bathroom sinks
Yes
Yes
Sinks
Kitchen only
Tubs and showers
Yes, any waste drain
Yes
Not stated
No
Toilets
Flushed for roots in sewer and septic lines
No
No
No
Garbage disposals
Yes, about 20 minutes
No
No
No
Grease traps
2 lb per 100 gallons
Not stated
Not stated
Not stated
Septic tanks
Yes; not in Massachusetts
Safe
Not stated
Safe
From ComStar’s product page, directions and question page, Instant Power’s product page, Roebic’s directions and label, and SC Johnson’s product page and Amazon listing, read Oct 21 and 22, 2026.
On PVC, three makers say yes outright and none says no. The pipe rows that bite are the metal ones. A tub’s chrome overflow plate, a brass pop-up and a stainless kitchen sink all sit right where crystals land if you pour fast.
The toilet row isn’t a yes from ComStar for a stopped bowl. Its maker page says the beads can be flushed to fight roots in sewer and septic lines, which is a different job.
How strong each bottle is, from the safety sheets
All four are mostly sodium hydroxide, the chemical name for lye or caustic soda. The sheets give the numbers.
Bottle
Sodium hydroxide
Other ingredients
pH
Sheet
ComStar Pure Lye
99.9%
None listed
14 (5% solution)
Rev. Dec 12, 2022
Instant Power Crystal Lye
100%
None listed
13 to 14
Rev. Jul 1, 2020
Roebic Crystal Drain Opener
96 to 100%
Sodium chloride 0 to 2%; sodium carbonate 0 to 2%
Over 12.5
Rev. Mar 4, 2022
Drano Kitchen Granules
60 to 100%
Sodium chloride 10 to 30%; sodium stearate
Over 12
Rev. Jul 11, 2025
From each maker’s safety data sheet, plus SC Johnson’s ingredient page for sodium stearate, read Oct 21 and 22, 2026.
The strength gap is smaller than it looks. All four sit near the top of the pH scale, and all four burn skin and eyes. What changes is how much of the bottle is lye. A 99.9% bead is almost all active chemical, while Drano’s sheet allows as little as 60%, with salt as a flow agent.
Never use lye with or after these
The most dangerous lye job is the one where something else is already in the pipe. These lines come from the makers’ own sheets and labels.
Already in the drain, or nearby
What the makers say
Source
Acid drain opener (sulfuric or muriatic)
Violent reaction with acids
Instant Power safety sheet; Roebic directions
Bleach
Do not mix with bleach or any other household cleaners
Drano Granules safety sheet; Instant Power page
Ammonia
Splashing or release of hazardous gases may occur
Roebic directions; Instant Power page
Any other drain opener
Do not use if another product treated this clog
Drano Granules page; ComStar page
Aluminum, tin or zinc
Can form flammable hydrogen gas
Instant Power safety sheet
A plunger
Splashing may occur; don’t plunge
Instant Power page; Drano Granules page
A sealed system
Never use in a completely sealed system
Instant Power page
From Instant Power’s product page and safety sheet (rev. Jul 1, 2020), Roebic’s directions, ComStar’s product page and SC Johnson’s Drano Kitchen Granules page and safety sheet (rev. Jul 11, 2025), read Oct 21 and 22, 2026.
This is why I won’t pour lye into a drain someone already treated. Acid openers sit at the other end of the pH scale, and our sulfuric acid drain cleaner page has the same warning from the acid side. If you don’t know what went in before, flush with plenty of water or call a plumber.
Is crystal lye better than Drano gel or acid?
They’re different tools. Here’s how dry lye compares with the gel and acid openers people weigh it against.
Lye rows from this page’s sources. Drano Max Gel pH from SC Johnson’s safety sheet 350000040792 (May 25, 2021). Acid range from Pro Line’s and Black Swan’s safety sheets, as covered on our sulfuric acid page.
Crystal lye is stronger, ounce for ounce, than a gel, because there’s almost no water or bleach in the bottle. That’s the case for it on grease. The case against: gels pour through standing water as sold, while crystals mostly need the standing water out first.
Acid is stronger still and goes after paper and rags, which lye doesn’t. For a full lineup across all kinds, see our best drain cleaner guide.
Lye recalls: what the CPSC record shows
None of our four brands has a CPSC recall since 2018. Plenty of other lye has, and almost always for the same reason.
What we searched
Recalls since 2018
Most common reason
ComStar, Instant Power, Roebic, Drano
0
None
“Sodium hydroxide” products
14
Mostly packaging that wasn’t child-resistant
“Lye” products
11
Mostly packaging that wasn’t child-resistant
Latest
Apr 23, 2026
Pellet bags, risk of chemical burns
From the CPSC recall database, searched Oct 22, 2026. The two searches overlap; most recalls appear in both.
Most of those recalls were raw sodium hydroxide from chemical and specialty sellers, in bags or jars that weren’t child-resistant. Only one, from Belle Chemical in 2020, was sold as a drain cleaner, and it was recalled for its label. Instant Power posts a child-resistant packaging certificate for its 1 lb bottle.
My call: buy a bottle labeled as a drain opener, keep its cap on tight, and store it locked up, as every maker here says.
Safety gear and first aid, from the labels
Put this on before the cap comes off. The first aid lines are the makers’ own.
What
What the makers say
Source
Eyes
Chemical splash goggles; a face shield too, per ComStar’s sheet
All four safety sheets
Hands
Rubber or chemical-resistant gloves
Roebic, ComStar and Drano sheets
Body
Protective clothing; ComStar’s sheet names a synthetic apron
ComStar and Instant Power sheets
Your face
Stand back; cover the drain with a bowl or dish pan
ComStar, Instant Power and Roebic directions
Lye on skin
Flood with water, then rinse with vinegar
ComStar and Roebic labels
Lye in eyes
Flush with water for 15 minutes; get medical help right away
ComStar and Roebic labels; Instant Power sheet
Swallowed
Call a poison center or doctor right away
Instant Power sheet; Roebic label
Storage
Store locked up, out of reach of children
Instant Power sheet; Roebic label
From each maker’s safety sheet and label, read Oct 21 and 22, 2026. For a poisoning in the US, Poison Help is 1-800-222-1222.
The vinegar step on ComStar’s and Roebic’s labels is for skin, after a long flood of water. Don’t pour vinegar into a drain that still has lye in it. My call: keep a jug of clean water by the sink before you open the bottle, so a splash gets rinsed in seconds.
How to use lye to clear a drain
This order follows the makers’ shared steps. Read your own label first, since doses and water temperature differ.
1
Make sure nothing else is in the drain
No acid, no bleach, no other opener. Every maker here says not to use lye after another product.
2
Gear up
Splash goggles, rubber gloves and long sleeves. Open a window or run a fan.
3
Take out the standing water
Bail or sponge it into a bucket. Drano says not to pour into standing water, and the others say to remove it first.
4
Pull the strainer or stopper
Lift out a pop-up or basket strainer so crystals don’t land on chrome or brass.
5
Measure the dose with a plastic spoon
1 tablespoon to ¼ cup, by the label. Pour slowly, straight into the opening.
6
Add the label’s water and cover the drain
Hot or cold as your label says, then a bowl or dish pan over the opening. Don’t seal it.
7
Wait, then flush
15 to 30 minutes, then a long run of water. Overnight only for ComStar’s stopped-drain mix.
8
One repeat, then stop
If it’s still stopped, call a plumber and name the product in the line.
Rinse the measuring spoon in a bucket of water, not the sink you just treated, and cap the bottle before you do anything else. My call: tape the product name to the cabinet door until the drain runs clear, so whoever opens the trap next knows lye is in it.
When to put the lye down and call a plumber
Two of these come from the labels. The rest are my call.
Two doses didn’t clear it
Instant Power and SC Johnson both say to call a plumber after a second treatment fails. Tell them which product is in the line.
The clog got worse after lye
SC Johnson warns that too much product can cause stagnation or permanent clogging. My call: stop adding lye and call.
Every drain is slow at once
My call: that points to the main line, where a spoonful in one sink can’t reach. Our main line guide explains the signs.
Something solid went down
SC Johnson says not to use its granules on paper, plastic or metal objects. Those come out by hand or with an auger.
The pipe is galvanized or very old
Roebic rules out galvanized, lead and zinc pipe. If you can’t tell what’s under the sink, a plumber can.
Standing water with lye in it
Instant Power warns that standing water left from a first dose can burn. Don’t reach in; call.
These names come up in every lye search. Here’s what kept each off the list on Oct 22, 2026.
Bottle
What we found
Why it’s out
Thrift T-100, T-200 and T-600
Alkaline granular drain cleaner; every listing we found was sold by resellers, not Amazon or Thrift
We picked bottles sold by Amazon or the maker
Rooto 1030
Sold only by resellers on Amazon; one multipack showed 4 left
We picked bottles sold by Amazon or the maker
“Red Hot Devil” lye
Food-grade caustic soda, sold for soap and cooking
Not labeled as a drain opener, so no drain directions
Bell Bird crystal lye
Little-known brand, sold by a reseller
No maker documents we could check
Clean Shot crystal lye
1 left in stock
Under our stock floor for a little-known brand
Instant Power Professional 8886
Pro line, 12-pack with 4 left
Sold by the case; the 1650 is the same chemical for home use
People still search for Red Devil lye. The “Red Hot Devil” jar on Amazon now is a different product, sold as food-grade caustic soda. It may be the same chemical, but without drain directions on the label, it isn’t what I’d pour into a sink.
How to choose a lye drain opener in four questions
Question
If yes
If no
Did any other cleaner go in?
No lye. Flush with water or call a plumber
Keep going
Is it a toilet?
Not a lye job; use a toilet auger
Keep going
Is the drain fully stopped, or does it have a disposal?
ComStar Pure Lye
Keep going
Is it a tub, shower or bathroom sink?
Instant Power, or ComStar
Kitchen: Roebic, or Drano Granules with no disposal
Most homes need one bottle at most, kept locked up for the grease or hair clog a plunger didn’t move. If you live in an older house with galvanized steel drains, skip Roebic and check with a plumber before using any of them.
Questions people ask
Does crystal lye drain opener work?
On grease, hair and soap scum, yes; that’s what the makers say it’s for. Instant Power says it clears lines in 15 to 30 minutes. It won’t dissolve paper, plastic or metal objects, per SC Johnson, so those need a tool.
Is crystal lye drain opener safe for pipes?
ComStar, Instant Power and SC Johnson say their lye is safe on PVC and metal pipe. Roebic rules out aluminum, lead, zinc and galvanized pipe. Keep crystals off chrome, brass and stainless fixtures, as the labels say.
How do you use a crystal lye drain opener?
Take out the standing water, pour the label’s dose slowly into the drain, add the label’s water, cover the drain with a bowl and wait 15 to 30 minutes. Then flush. Doses run from 1 tablespoon (Roebic) to ¼ cup (ComStar).
Is crystal lye better than Drano?
For grease, crystal lye is more concentrated: 96 to 100% sodium hydroxide, against bleach and lye in Drano Max Gel. Gels pour through standing water; crystals mostly need it bailed out first. Drano also makes Kitchen Granules, a lye product.
Is lye a good drain cleaner?
For grease, hair and soap clogs, yes. It’s a poor choice for toilets, since three of our four makers rule them out, and for clogs from paper or solid objects.
Will lye damage PVC pipes?
Not per the makers. ComStar says it’s safe on plastic pipe, Instant Power says all pipes, and SC Johnson names PVC. Follow the dose; SC Johnson warns that too much can cause permanent clogging.
Is it safe to pour lye down the drain?
Yes, when it’s a drain product used as labeled: goggles, gloves, standing water out, the measured dose and a cover over the drain. Never after acid, bleach or another drain cleaner.
Can you use lye in a toilet?
Instant Power, Roebic and SC Johnson all say no. ComStar says its beads can be flushed to fight roots in sewer and septic lines, which isn’t the same as clearing a stopped bowl. Use a toilet auger instead.
Can you put lye in a garbage disposal?
Only ComStar allows it, with about a 20 minute stand. Instant Power, Roebic and SC Johnson all rule out disposals.
Should I use hot or cold water with lye?
Follow your label. Roebic says cold water to cut the heat. Instant Power adds 1 cup of hot water. Drano says hot but not boiling. ComStar uses hot water for a slow drain and a cold-water mix for a stopped one.
How long should lye sit in a drain?
Fifteen minutes for Roebic and Drano Granules, 15 to 30 minutes for Instant Power, and 15 minutes or longer for ComStar. ComStar’s mix for a fully stopped drain can stay overnight.
Lye drain cleaner made the clog worse. What now?
Stop adding product. SC Johnson warns that too much can cause stagnation or permanent clogging. Don’t plunge or reach into the water; call a plumber and name the product.
Is lye drain cleaner the same as soap-making lye?
The chemical is the same, sodium hydroxide. The difference is the label: drain products carry drain directions and warnings. Most CPSC lye recalls since 2018 were raw lye in packaging that wasn’t child-resistant.
Can I use lye after a sulfuric acid drain opener?
No. Instant Power’s sheet warns of violent reactions with acids, and acid makers say the same from their side. Flush with plenty of water or call a plumber.
How we picked these
Why trust me
I’m Isaac Daniels, a licensed journeyman plumber in Georgia (license #JP507711), and I’ve used all four picks. Every spec here comes from ComStar’s, Instant Power’s, Roebic’s and SC Johnson’s product pages and safety sheets, read Oct 21 and 22, 2026. Where I add advice of my own, it’s labeled as my call.
How I pick
Only genuine brand lye drain openers, new and in stock on Amazon, checked through Amazon’s product data the same night. Each one was sold by Amazon or its maker.
Lye sold only for soap or cooking, with no drain directions, was left out.
Specs from each maker’s own pages and safety sheets first.
Each card’s spec score comes from the five checks below. All four score 7.0 or higher.
CPSC recall search for all four brands: no recalls since 2018.
The spec score, check by check
Each check scores 0 to 10 and counts one fifth. Anything the maker doesn’t state scores a neutral 5. It’s our score from the makers’ documents, not a customer rating or a lab test.
Check (weight)
How it’s scored
Lye strength (⅕)
10 for an exact figure of 99% or more on the maker’s sheet; 9 for a range within 4 points; 7 for a wider range; 5 when not stated
Pipe guidance (⅕)
10 when the maker says which pipes are safe and names 3 or more metals to keep it off; 8 for safe pipes plus 1 or 2 metals; 7 for metals to avoid only; 5 when not stated
Directions (⅕)
10 for a dose and stand time for both slow and fully stopped drains; 9 for a dose, stand time and a repeat limit; 8 for a dose and stand time; 5 when not stated
Places named (⅕)
10 for 5 or more places, including disposals or grease traps; 8 for 3 or 4; 6 for 1 or 2; 5 when not stated
Splash and heat (⅕)
10 for a cover-the-drain step plus a water temperature rule; 8 for one of them; 5 for neither
Total
Average of the checks, to one decimal
Pick
Lye strength
Pipe guidance
Directions
Places
Splash and heat
Score
ComStar Pure Lye
10
8
10
10
10
9.6
Instant Power Crystal Lye
10
10
9
8
10
9.4
Roebic Crystal Drain Opener
9
7
8
6
10
8.0
Drano Kitchen Granules
7
8
9
6
8
7.6
Sources
ComStar International, Pure Lye Bead Drain Opener product page on comstarproducts.com (instructions for small drains, stopped drains, grease traps and septic tanks): read Oct 22, 2026.
ComStar International, Pure Lye 1 lb product page (item 30-500, purity, uses, precautions, first aid) and question page (“ComStar says” answers only) on comstarpurelye.com: read Oct 21, 2026.
ComStar International, Pure Lye Bead safety data sheet, rev. Dec 12, 2022 (composition, pH, protective gear, incompatible materials): read Oct 21, 2026.
Instant Power Corporation, Crystal Lye Drain Opener product page (uses, instructions, what it’s not for, pipe and septic claim): read Oct 21, 2026.
Instant Power Corporation, Crystal Lye safety data sheet no. 1650, rev. Jul 1, 2020 (composition, pH, reactivity, protective gear), and CPSIA certificate of compliance listing item 1650: read Oct 21, 2026.
Roebic Laboratories, Professional Strength Crystal Drain Opener product page and instructions page (directions, pipes and fixtures to avoid, first aid): read Oct 21, 2026.
Roebic Laboratories, Crystal Drain Opener safety data sheet, rev. Mar 4, 2022 (composition, pH, incompatible materials): read Oct 21, 2026.
SC Johnson, Drano Kitchen Granules product page on drano.com (features, where it works, directions, precautions) and ingredient page on whatsinsidescjohnson.com: read Oct 21, 2026.
SC Johnson, Drano Max Gel Clog Remover SDS 350000040792, rev. May 25, 2021 (pH): read Oct 20, 2026.
Amazon listings for B00PKNBK24, B071YVYX5P, B07MQBT4HS, B00BH34MEY and B077M6G2F6 (titles, model, seller, condition, stock), plus the left-out listings: read through Amazon’s product data, Oct 21 and 22, 2026.
U.S. Consumer Product Safety Commission recall database, searched for the four brands, “sodium hydroxide” and “lye”: Oct 22, 2026.
America’s Poison Centers, Poison Help line number.
Google results and People Also Ask for “crystal lye drain opener” and “lye drain cleaner”: seen Oct 21, 2026. Search volumes from Semrush, Oct 21, 2026.
