Small bathroom with a close coupled toilet, basin and white metro tiles

Blocked or overflowing toilet in London

Blocked or overflowing toilet

If a toilet is blocked or overflowing, stop flushing, turn off the small isolation valve on the cistern pipe or lift the float to stop it filling, and protect the floor. Try a plunger once. If it will not clear, or other toilets and sinks are backing up, the blockage is further down and needs a plumber.

Is it an emergency?

Photo for illustration

Blocked or overflowing toilet: tap what is happening

You see what to do right now, then send it through.

01Right now
02Your home
03Call back

Step 1

Right now

What is happening right now?

You need this when

If any of these is happening now, turn the water off at the stop tap first.

Blocked or overflowing toilet

The water rises to the rim when you flush
The toilet drains very slowly or gurgles
The cistern keeps filling and water runs into the pan or overflow
Water comes up in the shower or bath when the toilet is flushed
The toilet in the flat below or above is also blocked
There is a smell of sewage in the bathroom

Step by step

What happens from the first message to the written note at the end.

1
Stop the water
We isolate the cistern so it cannot keep filling, and protect the floor. If water has reached the flat below, we check there too.
2
Find where the blockage is
Pan, pan connector, branch pipe or main soil stack. If other fittings are affected, the blockage is shared and further down.
3
Clear it with the right tool
Plunger, toilet auger or drain rods, depending on where it is. We avoid harsh chemicals, which can damage old pipes and anyone working on them.
4
Fix the cause
If the cistern is overflowing, we repair or replace the fill valve. If the blockage keeps happening, we look at the fall of the pipe or the stack.

Blocked toilet or blocked drain?

If only one toilet is slow and everything else drains, the blockage is usually in the pan or the short pipe behind it. That is often wet wipes, too much paper, a child's toy or sanitary products. If the bath, shower or basin also gurgles or backs up when you flush, the blockage is further along, in the branch pipe or the soil stack.

In a converted London house, several flats can share one soil stack, the large vertical waste pipe usually on the back wall. If the stack blocks near the bottom, the lowest flat floods first, because waste from everyone above backs up into the lowest toilet or shower. If the toilet in the ground floor flat is rising when someone upstairs flushes, it is a shared blockage, not yours alone.

Overflowing cisterns and hard water

A toilet can also overflow from the top. If the fill valve in the cistern sticks open, water keeps running into the pan, or out of the overflow pipe to the outside wall. In older or concealed cisterns with an internal overflow, it just runs into the pan constantly.

Thames Water says all the water in its region is hard. Over time limescale builds up on fill valves and flush valve seals, which is one of the most common reasons London toilets keep running. The fix is usually a new fill valve or seal, not a new toilet. If the overflow pipe on your outside wall is dripping, that is the same fault showing from outside.

Who is responsible in a flat

A blockage in your pan or the pipe serving only your flat is usually yours, or your landlord's if you rent. 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.

A blocked shared soil stack in a block or conversion is usually the freeholder's to clear, while a blocked shared drain or lateral drain outside the building may be Thames Water's, since it took over most private sewers and lateral drains on 1 October 2011.

What to try before you call

If only one toilet is blocked and nothing else is backing up, one careful attempt is reasonable. Put old towels down, wear gloves and use a proper toilet plunger with a flange that seals in the bottom of the pan. Push gently first to get the air out, then work it up and down firmly about a dozen times. Do not keep flushing to test it, as that is how pans overflow.

Stop and call a plumber if the water is rising, if the plunger is not shifting anything after a few tries, if you know something solid has gone down, or if water is showing up in the bath, shower or the flat below. Those are signs the blockage is beyond the pan.

No prices online

Every job is priced after a look at it, by photo or a visit, and agreed before work starts.

What affects the price

Where the blockage is and how easy it is to reach decide the cost. A pan blockage is quicker than a stack or drain. We confirm the price once we know where it is.

What	Price
Clearing a blocked pan	price confirmed after a look at the job
Replacing a stuck fill valve or flush seal	price confirmed after a look at the job
Clearing a blocked soil stack or branch	quote on survey
Water damage to the flat below	quote on survey

No prices are shown on this site. Every job is priced after a look at it, by photo or a visit.

Asked questions

How do I stop a toilet overflowing?

Do not flush again. Take the cistern lid off and lift the float to stop it filling, or turn the small isolation valve on the pipe to the cistern with a flat screwdriver.

Can I use bleach or drain cleaner on a blocked toilet?

It rarely clears a solid blockage and can splash back when someone plunges or rods it. Tell the plumber if you have used any chemical.

My downstairs neighbour's toilet floods when I flush. Why?

That points to a blockage in the shared soil stack or drain below both flats. Stop flushing and tell the freeholder or managing agent, as it is likely a shared pipe.

Is a blocked toilet an emergency?

It is if it is your only toilet, it is overflowing, or sewage is coming up elsewhere. Otherwise it can usually be booked in.