How to unblock a toilet before calling a plumber

A blocked toilet is unpleasant but often fixable without help. The key is knowing when to stop. One careful go with the right plunger clears most blockages in the pan. Repeated flushing, chemicals and coat hangers are how a blocked toilet becomes an overflowing one, or a cracked pan.

Before you start

Stop flushing. Each flush adds more water to a pan that cannot drain, and that is how toilets overflow onto the floor and through the ceiling below.

If the water is close to the rim, take the lid off the cistern and lift the float arm, or push the float up, to stop it refilling. You can also close the isolation valve on the pipe to the cistern with a flat screwdriver.

Put old towels around the base of the toilet. Wear rubber gloves.

Step by step with a plunger

1. Use a flanged toilet plunger. The soft flange fits into the outlet at the bottom of the pan and makes a seal. A flat cup plunger meant for sinks will not work well.
2. Check the water level. You need enough water in the pan to cover the cup. If it is very full, bail some out into a bucket.
3. Seat the plunger. Put it into the bottom of the pan at an angle so it fills with water, not air. Then press it over the outlet.
4. Push gently first. The first push is to get air out without splashing.
5. Plunge firmly. Pull and push in a steady rhythm, keeping the seal, about a dozen times.
6. Lift and look. If the water starts draining, it is probably clear. If not, repeat a couple more times.
7. Test with one flush, with your hand ready on the float or the isolation valve in case it rises.

If it clears, run a second flush to make sure the pipe is fully open.

What not to do

Do not	Why
Keep flushing to test	It is how pans overflow
Pour boiling water in	It can crack the ceramic pan
Use caustic drain cleaner	It rarely shifts solid blockages and is dangerous if it splashes
Push a wire hanger down	It scratches the pan and can push the blockage further
Use a sink plunger	It cannot seal in a toilet outlet

When the blockage is not in the pan

If plunging does nothing, the blockage may be further along. Watch for these signs.

• The bath, shower or basin gurgles or drains slowly when you flush.
• Water rises in the shower tray when the toilet is flushed.
• Other flats in the building report the same problem.
• There is a sewage smell from other drains.

These point to a blockage in the branch pipe or the soil stack, the main vertical waste pipe that serves the building. Plunging will not reach it, and in a block it may not be yours to clear.

High rise flats and soil stacks

In Tower Hamlets, 80.7% of households live in purpose built flats, according to the 2021 Census (Nomis, TS044). In a tower on the Isle of Dogs or an estate in Bethnal Green, every toilet on your stack drains into the same pipe. If that stack blocks lower down, waste from the flats above backs up into the lowest toilets.

If you are on a lower floor and your toilet rises when someone above flushes, stop using it and tell the managing agent, housing provider or concierge. A shared stack is usually the building’s to clear. The Leasehold Advisory Service says the freeholder is usually responsible for communal pipes serving more than one flat.

Macerator toilets

Some flats, especially basements and studios carved out of other rooms, have a macerator toilet. It has a pump and grinder behind or beside the pan that chops waste and pumps it to the stack. These block more easily, because they cannot handle wipes, sanitary products or too much paper.

If your toilet has a box behind it and makes a whirring noise when flushed, it is a macerator. Do not plunge it hard. Switch it off at its fused spur and call a plumber. Plunging can push water back into the unit.

What usually causes the blockage

Most blockages in London flats are down to a few things.

• Wet wipes, even ones labelled flushable.
• Too much toilet paper in one go.
• Sanitary products, cotton buds and nappies.
• Children’s toys.
• Limescale narrowing the outlet over years in older pans. Thames Water says all the water in its region is hard.

When to call a plumber

Call a plumber if the plunger has not worked after a few goes, if water is rising, if something solid has gone down, if other fittings are affected or if it is your only toilet. Our blocked toilet page explains what the visit involves.

If the toilet has already overflowed and the water has gone through the floor, read our guide to a toilet overflowing into the flat below.

If you rent

A blocked toilet you caused is often yours to sort. A blockage in the building’s pipework is not. Under section 11 of the Landlord and Tenant Act 1985, landlords in England must keep sanitation installations, including toilets, in repair and proper working order. If the toilet keeps blocking for no clear reason, report it to your landlord in writing.