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Why Won't My Toilet Flush?
This is the opposite of the fault the rest of this guide covers, and it splits cleanly in two. Either the cistern is not delivering water to the pan, which is a mechanism problem you can usually see, or the pan is not clearing, which is a blockage. Telling them apart takes one look under the lid.
The Short Answer
Lift the cistern lid and flush. If the water level drops sharply and a good volume leaves the cistern, the mechanism is fine and you have a blockage somewhere past the pan. If the level barely moves, or the handle or button feels slack and disconnected, the fault is in the cistern and the drain is fine. Those two answers lead in completely different directions, so make that check before anything else.
If the Cistern Is Not Emptying
With the lid off, watch what happens when you operate the flush. You are looking for the drop valve or flap to lift and a substantial volume to leave quickly. A weak, slow release, or nothing at all, points at one of four things.
The water level is too low. A cistern that has only partly filled cannot produce a full flush, and the cause is usually a fill valve set too low or a partly closed isolator on the supply. Check the level against the fill line first, since it is the quickest thing to rule out.
The linkage has failed. On a lever cistern there is usually a plastic or metal arm connecting the handle to the flush valve, and these snap. The tell is a handle that suddenly moves with no resistance at all. On a button cistern the equivalent is a cable that has come adrift or a push rod out of position.
The flush valve is not lifting far enough. Cable operated dual flush units have an adjustment for exactly this, and one that has drifted or been set wrong gives a persistently feeble flush that never quite clears the pan.
Or the siphon has gone, on an older cistern. Traditional siphon flush units, still common in this city's older bathrooms, work by pulling water over a bend, and the diaphragm inside them perishes. The symptom is very characteristic: you have to pump the handle several times to get a flush, and it gradually gets worse over months. A perished diaphragm is a cheap part and a straightforward replacement, though the cistern usually has to come off to reach it.
If the Cistern Empties but the Pan Does Not Clear
Now you have a blockage, and the useful question is how far along it sits. There are three broad positions and each behaves differently.
In the pan itself, in the trap immediately below the bowl. Water rises, hesitates, and then drains away slowly, or does not. This is the commonest and the most likely to clear with a plunger or a toilet auger. A flanged plunger, which has an extra lip that seats into the outlet, works far better here than a flat sink plunger.
In the branch between the toilet and the soil stack. The pan clears slowly and you may hear gurgling from a nearby basin or bath as air is pulled through. An auger can reach some of these; beyond that it is a rodding job.
In the soil stack or the drain below, which is where it stops being only your toilet. The signs are distinctive and worth knowing, and they are covered below.
One thing to avoid throughout: do not keep flushing to see whether it clears. Each flush adds several litres to a pan that is not draining, and the usual outcome is an overflow onto the floor, which in a flat means somebody else's ceiling.
Clearing a Blocked Pan
In order, cheapest and least invasive first, and none of this requires anything specialised beyond a plunger.
- Bail the pan down if it is full to the rim, using a jug and a bucket, so you have room to work without displacing water onto the floor.
- Hot water and washing up liquid. Not boiling, since very hot water into a cold ceramic pan can crack it and the pan is the expensive part. Hand hot, a generous squirt of detergent, and fifteen minutes. This alone shifts a surprising number of soft blockages.
- A flanged plunger. Seat it fully into the outlet at the bottom of the pan so it seals, then use firm steady pushes rather than violent ones. You are trying to move a column of water back and forth, and violence mostly splashes.
- A toilet auger, sometimes called a closet auger. This is a short cranked auger with a sleeve designed to go round the trap without scratching the ceramic. A general drain snake is the wrong tool and will mark the pan.
- If none of that moves it, stop. Chemical drain unblockers are a poor idea in a toilet: they do nothing to the things that usually block one, and they leave a pan full of caustic solution that whoever comes next has to deal with before they can put a hand or a tool in.
What Actually Blocks Toilets
Worth knowing, because it changes what you do afterwards rather than just now. The overwhelming majority of blocked toilets we attend contain wet wipes. They do not break down, they knit together into a mass, and the word flushable on the packet refers to whether they leave the pan, not whether they reach the sewer.
After wipes: sanitary products and nappies, which behave the same way, and cotton buds, which individually pass and collectively form a lattice that catches everything else. Then, in older properties, a build up of scale and debris narrowing the trap over years, so that a toilet which coped fine for a decade starts blocking regularly on normal use.
And occasionally something structural. A pan connector that has slipped, leaving a lip for waste to catch on, or a soil branch laid with too little fall. Those present as a toilet that blocks repeatedly with nothing unusual going down it, which is the signal to stop clearing and start looking at why.
The practical upshot is simple and slightly boring: nothing but the obvious goes down a toilet. It is a effective preventative and it is free.
When It Is Not Your Toilet
This is the case people miss, and it matters most in a flat. If the blockage is in the shared soil stack or the drain below it, the symptoms show up in your property but the fault is not in it, and no amount of plunging your own pan will help.
The signs are fairly reliable. Water rising in the shower tray or bath when the toilet is flushed. Gurgling from a basin or bath when the toilet is used, or from the toilet when a bath is drained. More than one fitting slow at the same time. And most conclusively, a neighbour in the same close with the same problem the same week.
If that is what you have, plunging is the wrong response and can make it worse by pushing waste further into a stack that is already full. The right step is to stop using the affected fittings, and to find out whether other flats are affected before anyone starts work, because that determines both what needs doing and who is responsible for it.
Your Toilet or the Building's Stack?
In a tenement this distinction is the whole job, and it is worth understanding because it decides who pays as well as what gets done. A traditional Glasgow tenement has a soil stack serving the same room in every flat up the close, a single vertical pipe taking waste from four or eight bathrooms stacked above one another. Your toilet connects to it by a short branch, and that branch is yours. The stack is common.
So a blockage in your branch is your repair and a blockage in the stack is the building's, and the symptoms differ in a way you can read from inside your own bathroom. A fault in your branch affects only your fittings. A fault in the stack affects other flats too, and it shows up as waste backing up into the lowest fittings in the close, which is why the ground floor flat frequently discovers a problem that originated three floors up.
That has a practical consequence worth acting on: before you spend an afternoon on your own pan, knock on a door or two. Establishing that the flat below has the same issue this week takes five minutes and changes the entire course of the repair. If your building is factored, a stack problem goes to the factor rather than being arranged by whichever household noticed first, and starting there avoids one flat paying for work on common pipework.
The other local pattern is the converted flat with a long soil branch. Where a bathroom was moved during a subdivision or a refit to make better use of a large room, the toilet can end up several metres from the stack on a branch with very little fall. Those block repeatedly on entirely ordinary use, and the honest answer there is usually not a better plunger but a look at the fall on that run.
When to Call Someone Out
Call when a plunger and an auger have not shifted it, when more than one fitting is affected, or when there is any sign the stack rather than your branch is the problem, because that needs establishing properly before anyone works on it. Also worth calling for a toilet that blocks repeatedly with nothing unusual going down it, since that is a fall or a connector problem rather than a blockage and clearing it again will not last. Paul leads the drain team and Kyle runs the jetting, and on a suspected stack issue we will tell you plainly whether it looks like common pipework, which matters for who arranges and pays for the work.
Toilet Installation in GlasgowCommon Questions
Take the lid off and flush. A cistern that empties sharply and a pan that does not clear means a blockage. A cistern that barely empties, or a handle with no resistance, means the mechanism. That one observation splits the problem in two and takes ten seconds.
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Read Next
Full guide
How to Fix a Running Toilet
Water is either passing from the cistern into the pan, which is the flush valve seal, or the cistern is overfilling and spilling into the overflow, which is the fill valve.
Why Does My Toilet Keep Running?
Listen to the pattern rather than the noise.
How to Fix a Running Toilet With a Button Flush
Take the button out of the lid first, because you cannot get the lid off with it in place on most designs.
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