DIY
Do Drain Cleaners Actually Work?
Caustic, acid, bleach-based and enzyme cleaners compared by the job they do, the risks, and what to use instead.
DIY
To unblock a drain yourself, first work out which drain is blocked: one slow fixture is a local blockage you can usually reach, while several fixtures or an overflowing gully trap mean the shared line outside. Then escalate in order: hot water and dish soap, a plunger, the trap's cleaning cap, a drain snake, and drain rods for outside drains. Home remedies and chemicals come a long way down that list. If water is not moving at all, or it is coming up outside, our drain unblocking service is the faster route.
Clearing a blocked drain is something you are legally allowed to do yourself in New Zealand. The Plumbers, Gasfitters and Drainlayers Board permits it as long as you do not alter or repair the inspection pipe or ventilation pipe. Anything beyond clearing, such as replacing or relaying pipe, is restricted work for a PGDB-licensed drainlayer. This guide stays inside that line.
Count the fixtures. If one basin, shower or sink is slow and everything else drains normally, the blockage is in that fixture's own trap or waste pipe, usually within a metre or two of the plughole. If several fixtures are slow, gurgle, or back up into each other, the blockage is further down, in a pipe they share. Then look at the gully trap outside: that one observation tells you which side of the house the problem is on.
The gully trap is the grated dish at ground level outside, usually against the wall near the kitchen, laundry or bathroom. Lift the grate. If it is full of standing wastewater or overflowing, the blockage is downstream of it, in the drain that runs out to the street. If it is empty while fixtures inside are backing up, the blockage is between the house and the gully. Our guide to the signs of a blocked drain goes through the other clues in more detail.
| What you see | Where to start |
|---|---|
| One fixture slow, the rest fine | Plunger, then the trap's cleaning cap if it has one, then a hand snake through the plughole |
| Two fixtures in one room | The branch pipe serving that room: a hand snake through the plughole |
| Fixtures across the house, gully overflowing | The outside drain: rods from an inspection point, or call |
| Wastewater in the street, or neighbours affected | Possibly the public main: call Watercare on (09) 442 2222, option 1 |
That last row matters before you spend anything. Watercare owns and clears the public wastewater network, and private drains belong to the property owner. Our guide to who is responsible for a blocked drain shows where the boundary usually sits.
For a single slow sink, basin or shower, the quickest fix is mechanical: pull out what you can reach from the plughole, then use a plunger with the overflow sealed. That clears most hair and soap blockages in a few minutes. If the plunger does not shift it, opening the trap's cleaning cap, if it has one, is the next quickest step. Pouring things down the drain and waiting is slower, and often does nothing.
The order below runs from the gentlest and cheapest to the most involved. Stop at the step that works. If a step makes no difference at all, the blockage is probably beyond its reach, so move on rather than repeating it.
Hot water can soften and move a small, recent build-up of fat or soap in a kitchen or basin waste, which is why it sometimes works on a slow drain. It will not clear hair, wipes, roots or anything solid, and it does nothing to a blockage further down, where the water has already cooled. Use hot tap water rather than a boiling kettle: it is nearly as effective on soft grease and kinder to plastic pipe and porcelain.
There are two reasons for caution with boiling water. Plastic drainage pipe is made from PVC, and manufacturers rate it for continuous flows up to about 60 °C (Vinidex technical note). An occasional kettle is a short, hot pulse rather than continuous flow, but repeated kettles poured into a pipe that cannot drain are well outside that rating. And never pour boiling water into a toilet bowl: a sudden temperature change can crack the porcelain.
If the drain is fully blocked, hot water simply sits on top of the standing water and cools. It also makes anything you do next, such as plunging, more likely to splash scalding water at you.
A good squirt of dishwashing liquid followed by a jug of hot tap water helps grease and soap slide, because detergent is designed to loosen fat. Give it ten minutes, then run the tap. It is worth trying on a slow kitchen sink or a toilet that is draining sluggishly. It is not a fix for hair, which needs to be pulled out.
Rarely. Baking soda (sodium bicarbonate) and vinegar (a weak acetic acid) react to give carbon dioxide gas, water and sodium acetate. The fizzing is the gas escaping, and it is mostly over within a minute. What is left in the pipe is a mild salty solution with no real power against hair, grease mats, wipes or roots. It can freshen a smelly basin waste, but it is not a blockage clearer.
The chemistry is the same reaction used in school volcano experiments (the reaction is sodium bicarbonate plus acetic acid giving sodium acetate, water and carbon dioxide). The two ingredients largely cancel each other out. That is why people who try it on a genuinely blocked drain usually find the water still sitting there afterwards.
You can. Household vinegar is a dilute acid and will not harm your pipes in normal amounts. Leaving it overnight does no damage, but it does not make it work any better either. Vinegar is a reasonable deodoriser for a basin or shower waste. It will not dissolve a blockage.
It is safer, and on a slow drain caused by a light soap film it may do just as much. On a real hair clog, neither is the best choice: a plastic hair-removal strip or a hand snake pulls the hair out, which beats trying to dissolve it.
It is a popular home tip that salt, often with hot water, scours grease and keeps drains fresh. We know of no good evidence that it does. Table salt (sodium chloride) dissolves readily in water, so once it is wet it has no scrubbing action, and salty water does not dissolve fat or hair. A spoonful is harmless, but it is not a fix or a preventative.
What actually keeps a kitchen drain clear is keeping fat and food out of it in the first place: scrape plates, wipe greasy pans, and use a sink strainer. Our guide on what not to put down the drain has the short list of habits that work.
A plunger works by pushing and pulling a column of water against the blockage, so it needs a seal and it needs water. Use a flat cup plunger on sinks, basins and showers, and a flanged plunger on a toilet. Seal the overflow hole with a wet cloth, make sure the cup is covered by water, then give ten to fifteen firm strokes without breaking the seal. Pull the plunger off sharply and see if the water drops.
If two or three rounds of plunging make no difference, stop. The blockage is either too firm or too far down for a plunger, and the trap's cleaning cap or a snake is the next step.
The trap is the curved or bottle-shaped fitting under a sink or basin. It holds a little water to stop smells coming up the pipe, and it is where hair, food scraps and grease collect. Many traps have a screw-off base or a cleaning cap (sometimes called a cleaning eye) made to be opened by hand for exactly this. Opening it and clearing what is inside is as far as DIY goes: the trap itself stays connected.
If the trap has no cleaning cap, or clearing it would mean undoing the trap from the pipe, leave that to a plumber. Removing or disconnecting a trap or waste pipe counts as sanitary plumbing, which is restricted work, and it is not on the PGDB's list of jobs householders may do. A hand snake through the plughole is the DIY alternative.
Shower wastes are usually cleared from above: lift out the grate or any insert and pull out the hair. A cheap hair catcher on the grate prevents most repeats. The shower guide in the fixture list at the end of this page goes into tile wastes and soap scum in more detail.
A drain snake, or hand auger, is a coiled steel cable that you feed into a pipe and turn with a handle, so its tip grabs or breaks up the blockage. It reaches well past where a plunger works. Feed it in through the plughole (or an open cleaning cap) until you feel resistance, lock the cable, turn it while pushing gently, then pull it back out with whatever it has hooked. Flush with hot water afterwards.
Use a toilet auger, which has a guard over the cable, for toilets: an ordinary snake can scratch the porcelain. Most household hand snakes reach a few metres, enough for a fixture waste or a branch pipe, but not the main drain under the garden. If the cable keeps stopping at the same point and nothing comes back on it, do not force it, especially in an older house with clay or earthenware pipes.
Yes, on soft blockages in the outside drain, such as paper, wipes or a build-up of waste, if you can get the rods into the pipe. Drain rods are stiff sections that screw together, with a plunger or corkscrew head on the end. They go in from an inspection point or the gully trap, never from inside the house. They will not clear roots, a collapsed pipe or set fat, and old earthenware pipe can be damaged by heavy pushing.
The outside drain guide listed at the end of this page covers gully traps and stormwater drains in more detail. If the outside drain keeps blocking in the same place, rods are only buying time. A CCTV drain survey shows whether it is roots, a dropped joint or a crack.
Slowly, and only on the right job. Enzyme and bacterial cleaners digest organic film, such as fat, soap and food residue, over hours to days. They suit a drain that still flows but is slow or smelly, and regular dosing can help keep a kitchen or basin waste clear. They will not clear a full blockage, because they need flow to reach it, and they do nothing against roots, wipes or objects.
Follow the label: most are dosed last thing at night so the product sits in the pipe while nothing is used. Avoid pouring bleach into the same drain around the same time, as it is designed to kill the bacteria these products rely on.
Only as a late step, only on a single slow fixture, and only exactly as the label says. Caustic and acid drain cleaners can dissolve hair, soap and grease near the plughole, but they cause chemical burns, they can splash back, and in a fully blocked drain they just sit in the standing water, waiting for the next person to open the pipe. Never mix two products, and never plunge afterwards.
If you do use one, wear gloves and eye protection, keep the room ventilated, and tell anyone who comes to clear the drain what you have put in it. If a drain cleaner is swallowed, or splashes on skin or into eyes, call the National Poisons Centre on 0800 764 766 (24/7). Our guide to whether drain cleaners work compares the types, what each clears, and the safer alternatives.
A badly blocked drain is one where water is not moving at all, several fixtures are affected, or the gully trap is overflowing. Stop using water first. Then find the blockage: if it is one fixture, work through the plunger, the trap's cleaning cap and a snake. If the gully is full, the blockage is in the outside drain, and rods from an inspection point are the only realistic DIY tool. Do not pour chemicals into standing water.
Every flush, tap and wash cycle adds volume to a drain that cannot take it, and it will surface at the lowest opening, often a shower or floor waste. Keep children and pets away from any overflow, wear gloves if you have to clean up, and wash hands thoroughly afterwards. Our emergency drainage line runs 24/7.
A drain that is badly blocked outside is the point where professional equipment earns its cost. A drainlayer clears it from the gully or an inspection point with a powered drain machine, or with hydro-jetting where fat or silt lines the pipe, and can put a camera down afterwards to see why it happened.
Stop when you have tried the plunger, the trap's cleaning cap and a snake without any change, when the blockage is in the outside drain and you have no rods or no access point, when wastewater is coming up inside, or when the same drain blocks again within weeks or months. Repeat blockages almost always have a physical cause in the pipe, such as roots or a damaged joint, that no amount of DIY clearing will fix.
We can tell you on the phone whether it sounds like a DIY job or not. If it is a job for a drainlayer, we arrange one from our network. Our blocked drain cost guide explains what drives the price, and you can request a free estimate.
The method changes a little depending on the fixture, because each has its own trap, pipe size and usual culprit: hair in showers and basins, fat and food in kitchen sinks, paper and wipes in toilets, leaves and silt in outside drains. These guides go step by step for each one.
It saves a lot of wasted effort. Run each fixture and watch what happens elsewhere, then lift the outside gully grate. One slow fixture means its own trap or waste pipe. Several fixtures, or a full gully, means the shared drain outside, which a plunger or hand snake inside the house will not reach. Ten minutes of checking tells you whether you need a plunger, rods, or a drainlayer.
Yes. Hand snakes and rod sets are sold at hardware stores, and some hire shops rent powered drain machines. A hand snake suits a fixture waste. Rods suit a soft blockage in the outside drain. Powered machines are a different matter: in inexperienced hands they can kink, jam or damage older earthenware pipe, so think twice before hiring one for a main drain.
Only with long rubber gloves, and only to scoop out leaves or debris sitting on top. Gully water is wastewater from the kitchen, laundry or bathroom and carries germs. Keep cuts covered, do not touch your face, and wash your hands and arms well afterwards. If the gully is full and not draining, the blockage is further down the pipe and scooping will not clear it.
Give each step a fair go, then move on. If plunging, the trap's cleaning cap and a hand snake have made no difference, more of the same rarely helps. If the gully is overflowing, wastewater is coming up inside, or several fixtures are affected, call straight away: those blockages are in the shared line, and the longer it overflows, the bigger the clean-up.
Because clearing removes the blockage, not the reason it formed. A trap full of hair will block again if hair keeps going down it, which a strainer fixes. A drain outside that blocks every few months usually has a physical cause such as roots, a dipped section or a damaged joint. A camera survey shows which, so you stop paying for the same clear.
Tell us what it is doing and we will tell you what it probably is, what it takes to fix, and what that should cost.