A toilet that will not flush properly
A weak flush and a blocked toilet look the same from the doorway and need different fixes. One pail of water tells them apart, and it takes ten seconds.
If it turns out to be a blockage that will not clear, or the problem is further down the line, that is our drain and toilet declogging service. Most weak flushes are a small part in the tank and you can check them yourself first.
The pail test
Drag the drawing sideways to see all of it.
Fill a pail and pour it into the bowl in one steady go, the way you would flush with a tabo.
- The bowl clears normally: the drain is open. The fault is in the tank or the water reaching it. Read on.
- The water rises and drains slowly, or not at all: it is a blockage. Our guide on unclogging a toilet covers what to try.
If your toilet has no tank and is always flushed with a pail, the pail test is the whole diagnosis. A slow bowl is a blockage.
Inside the tank: four things to check
Lift the lid off the tank. You are looking at these, in this order.
1. The water level
The water should sit about an inch below the top of the overflow pipe, the open tube in the middle. Lower than that and every flush is short of water. The fill valve has an adjustment, usually a screw or a clip on the float, to raise it.
2. The flapper and chain
The rubber flapper at the bottom lifts to release the water. If the chain is too slack it does not lift far enough. If the flapper drops shut too early, only part of the tank goes into the bowl. A flapper that leaks lets the tank drain between flushes, which is the fault on our toilet keeps running page.
3. The rim holes
The small holes under the lip of the bowl, and the larger jet at the bottom on many toilets, clog with calcium, lime and rust. The flush comes out feeble all round the bowl. Clear them with a bent wire.
4. How fast it refills
Flush and watch. A tank that takes a long time to fill gives a weak second flush. That can be a worn fill valve, or it can be the house.
When it is the house, not the toilet
Many houses here fill their toilets from a roof tank or through a pump. If the tank is low or the pump is weak, the toilet refills slowly and flushes badly, and changing toilet parts will not help. If the shower is weak too, start with low water pressure.
Two more causes sit beyond the toilet. A blocked vent stops air getting into the drain, so the bowl gurgles and empties sluggishly. A blockage in the main line shows up as several slow drains at once, or water rising in the floor drain when you flush. Both need a plumber.
Questions about a toilet that will not flush
- How do I tell a blocked toilet from a weak flush?
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Pour a pail of water into the bowl in one go. If the bowl clears normally, the drain is open and the fault is in the tank or the supply. If the water rises and drains slowly, it is a blockage.
- Why does my toilet flush fine in the morning and badly at night?
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Usually because the tank refills slowly when the house pressure is low, so the second and third flush of the evening start with a tank that is not full. On a house fed from a roof tank or a pump that points at the supply, not the toilet.
- Can I fix a weak flush myself?
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Often, yes. Setting the water level, adjusting the chain and cleaning the rim holes need no special tools. A flapper or fill valve is a small part and a short job. A blocked vent or main line is not a do-it-yourself job.
- What if other drains are slow too?
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Then it is probably not the toilet. A toilet that flushes badly while the floor drain or shower is also slow, or water that rises in the floor drain when you flush, points to the main line. That needs a plumber.
If you would rather chat
A written message reaches us with the detail already in it, so we know what is wrong before we ring you back. For a quick question first, the chat button sits in the corner of every page.
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Emergency Repairs Available 24/7
Blocked, or slow everywhere?
Toilets, floor drains and the main line are part of our drain and toilet declogging service. Send us the problem and say what the pail test showed.
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