Quick answer
A weak flush comes from the cistern or from a blockage in the pipe. A blocked toilet is an emergency if sewage or water comes up, or if it is your only toilet and will not clear. Otherwise it can often wait until morning. Mark your request urgent if sewage comes up, because that tells the engineer it cannot wait.
Cistern problem or drain problem?
Start by looking at what the water does. A cistern problem gives a weak or short flush, while the bowl still empties. A drain problem leaves the water high or slow to go down.
Now check the rest of the home. If the sink, bath or shower drains slowly or gurgles too, the problem sits further down the pipe. That happens because all of them share it. Our guide to the warning signs of a blocked drain lists more clues to look for.
Common cistern causes
Lift the cistern lid and look inside, because the cause often shows there. These are the usual suspects:
- A low water level, so the flush has too little water behind it
- Blocked jets under the rim of the bowl, which weaken the rinse
- A worn flap or seal that lets water leak out before you flush
A low level is the easiest to spot, since the water should sit just below the overflow tube. If it sits well below, the float may need a gentle change. However, if you are not sure what you are looking at, leave it alone and ask the engineer.
Safe steps to try first
Try these in order, and stop if the bowl rises towards the rim. Each step is gentle, yet none should be forced.
- Do not flush again. Wait a few minutes to see if the water level drops.
- Use a flange plunger, not a flat sink plunger, so it seals around the outlet.
- Push down gently to push out the air, then pull up sharply.
- Repeat 10 to 15 times, keeping the seal tight.
- Flush once, and only if the water level has dropped.
If the bowl is near the rim, close the small valve on the pipe that feeds the cistern. That stops more water coming in. Never pour bleach or drain cleaner into a blocked toilet, because chemicals rarely shift a solid blockage and can harm older pipes.
When it is the drain, not the toilet
Plunging will not help if the blockage sits past the toilet. Signs include gurgling from other drains, water that backs up in a sink, or a smell near an outside cover. A blocked vent pipe can cause gurgling too, yet that job needs an engineer.
In that case, treat it as a blocked drain. The blocked toilet page covers this fixture, while the blocked drains page covers the whole run of pipe. Local pages cover blocked drains in York, blocked drains in Selby and blocked drains in Tadcaster.
Some engineers use water jets and some use rods, because the right tool depends on the blockage. See drain jetting versus drain rods for the difference. The hidden signs of a blocked drain are worth a read as well.
If sewage or water is coming up
Sewage in the home is urgent because it can spread germs. Stop using all the toilets, sinks and the washing machine. Keep children and pets away, and wash your hands if you touch it.
The emergency drain services page explains what to include in a request. The request form stays open 24/7. Mark it urgent, say where the water comes from, and ask the engineer for a written quote before work starts. You can send it on the contact page, and the locations page lists each area.
For an urgent problem, see the emergency plumber page for York or the emergency plumber page for Selby.
Stop it happening again
Flush human waste and toilet paper only. Yorkshire Water's blockages page says nearly 50% of blockages in Yorkshire come from wipes. It also says wipes should never go down the toilet, even biodegradable ones.
Nappies, cotton buds and sanitary items do not break down like paper either. Use a modest amount of paper per flush, especially in an older home, since narrow bends snag easily.
The same rule applies in the kitchen, where fat and food waste cause many blockages. For that side, our guide to preventing blocked drains in the kitchen covers it.
Related guides
Frequently asked questions
Why won't my toilet flush properly?
The cause is usually in the cistern or in the pipe below the bowl. A low water level or a partial blockage is the most common pair. A plunger clears many partial blockages, while other causes need a closer look.
Is a blocked toilet an emergency?
Yes, if sewage or water comes up, or if it is your only toilet and will not clear. In other cases it can wait until morning. Still, mark the request urgent if sewage comes up.
Can I use bleach or drain cleaner to unblock a toilet?
It is best to avoid them, because chemicals rarely shift a solid blockage. They can harm older pipes and seals as well. A plunger is the safer first step.
Is a weak flush the same as a blocked toilet?
Not quite. A weak flush still clears, but a blocked toilet will not clear however often you flush. Act early on a weak flush, because it can turn into a full blockage.
