Before you start
Put on rubber gloves. If you've already poured in a drain cleaner, don't plunge: the chemical can splash up into your face, so tell whoever comes what you used. Never follow one drain product with another, or with bleach, because some mixtures give off toxic fumes. If sewage is backing up outside, stop using water in the house until the drain is cleared.
One fixture or the whole house?
Start by working out how deep the blockage is. A single slow basin or shower usually means hair, soap or food caught in the trap or the first stretch of pipe, and that kind is often within your reach.
When the toilet, shower and basins all drain slowly together, or the shower rises as someone flushes, the drain that carries everything away from the house is blocked. A plunger won't get there, and running more water just sends the overflow somewhere you'd rather it didn't go.
Clearing a sink, basin or shower
Remove what you can see
Take out the plug or lift the shower grate and pull out the hair and gunk by hand. A bent wire coat hanger reaches a little further down. Quite often that's the whole blockage.
Block the overflow
Basins and baths have an overflow hole near the rim. Hold a wet cloth over it so the plunger pushes down the pipe instead of out the hole. On a double kitchen sink, put the plug in the other bowl.
Plunge with a good seal
Leave enough water to cover the plunger cup. Push down gently to squeeze the air out, then pump hard a dozen or so times without lifting the cup off. Pull it away and watch whether the water drops. Keep going while it's improving.
Rinse it through
Once it runs, send plenty of hot tap water after it to carry the loosened gunk away. Skip the jug of boiling water: it's hard on plastic waste pipes and can crack a cold toilet bowl.
A blocked toilet
Stop flushing. Each flush adds water to a bowl with nowhere to send it, and the next one can spill onto the floor.
Use a toilet plunger, the kind with a soft flange that sits into the outlet at the bottom of the bowl. Work it firmly a few times, then let the water level settle before you try a single flush. If a few honest goes don't shift it, or it blocks again within days, the problem is likely further along the line. Our page on blocked toilets explains what a plumber does next.
Drain snakes, and the line you shouldn't cross
PGDB's list of what a homeowner may do includes clearing a blocked drain, as long as that doesn't involve altering or repairing the inspection pipe or the vent pipe in any way. A small hand-held drain snake fed down the plughole is one way to clear a blockage without touching either.
The same list puts fixing or unfixing any trap, waste pipe or vent pipe on the side a homeowner can't do. So unscrewing the trap under the sink to clean it out is a plumber's job, as is anything that means taking a pipe apart. Leave powered drain machines to the trade as well: forced into an old pipe by someone unpractised, they can turn a blockage into a broken drain.
Stop and ring a plumber or drainlayer if
- More than one fixture is slow or blocked at the same time.
- Water rises in the shower, a floor waste or the gully trap when something else drains.
- The gully trap outside is overflowing.
- Other fixtures gurgle while the blocked one empties.
- A few proper goes with the plunger haven't moved it.
- You've already tried a chemical cleaner and it hasn't worked.
- The same drain keeps blocking.
What the tradie will do
A plumber or drainlayer will find where the blockage sits, often through an inspection point outside, then clear it with a drain machine or a high-pressure water jet (hydro jetting). If it keeps coming back, a camera run through the pipe (CCTV drain inspection) shows whether roots, a crack or a sagging section is to blame.
Sometimes the blockage turns out to be in the council's or water provider's pipe, and then the process depends on where you live. Whanganui District Council says finding the blockage is the plumber's job, and the council gets the invoice when it's in the council network. Napier City Council won't pay for camera inspections or jet cleaning used to find the cause. Whangārei District Council asks you to contact it before anyone else. Who fixes a blocked drain has each provider's rule that we've confirmed.
Keep it from happening again
- Wipe greasy pans with a paper towel and bin it, instead of washing fat down the sink.
- Flush only toilet paper. Tauranga City Council puts most wastewater blockages down to wet wipes, fats and cooking oils.
- Fit a hair catcher over the shower and bath outlets.
- Keep leaves, soil and mulch off the gully trap grate.
What we would do
Give the plunger a fair go on one slow fixture, and leave the chemicals on the shelf: they rarely reach a stubborn blockage and they make the job riskier for whoever comes next. If two fixtures play up together, put the plunger down and ring. That blockage is in the main drain, and a drainlayer or a plumber who specialises in blocked drains can clear it before it overflows inside.