Why Your Toilet Won’t Flush – 4 Common Problems and How To Fix Them

by Dan | Last Updated: April 29, 2023

Nothing gets on your nerves like a toilet that won’t flush or a toilet not flushing all the way. I imagine it can also be pretty much awkward especially for your guests and kids when they have just gone number two.

Luckily, you don’t have to call your local plumber whenever there’s a ‘toilet-won’t-flush’ alert. As you’ll soon find out, even a rookie DIY homeowner could troubleshoot and also remedy a toilet system that refuses to do its work.

What Would Cause A Toilet Not To Flush?

1. A Bent Or Warped Flapper

   A poorly seated flapper is the major culprit in toilets that won’t flush. Also known as the ‘flush valve seal,’ this refers to the plug that opens and closes the drain hole.

   It allows the water to rush down into the bowl when you flush and also closes the drain hole to allow enough water to accumulate in the cistern in readiness for the next flush.

   Usually, the flapper is found in the bottom-most part of the tank and connects to the flushing handle via a chain.

   If no water comes forth after pulling the handle, the chances are that it’s not seated well on the outlet. Usually, merely jiggling the handle should position it well.

   If jiggling does not work, then you might want to lift off the lid and check out what the problem could be. After lifting off the cover, check out to see whether the chain is connected to the flapper.

   Sometimes the chain may come disconnected from the handle and work its way to the bottom. If that’s the case, try to reattach it and flush again (more about this below).

   If the chain is still intact, then the chances are that the flapper isn’t seated properly. Try to re-seat it with your hands. If this corrects the situation, you are safe. If it doesn’t, then it’s very likely that the flapper is worn out and needs replacement.

   So, reach for any large container in the bathroom, fill it with water and manually flush your ‘business’ down the drain. Next, rush to the hardware or home improvement store and ask for a flapper and replace the worn out one. Learn how to replace the flapper here.

2. A Faulty Lift Chain

   For a flapper that has just been replaced, the problem might be the chain itself. In case the chain is still connected to the flush seal valve, inspect to see it has too much slack. If the lift chain has a lot of stretch to it, it won’t be able to lift the flapper high enough to allow the water to run down.

   To fix this, simply adjust the length of the chain by shortening it. This allows the flapper to lift high enough for a full flush. You’ll need needle-nose pliers for this.

   At times, the chain may have snapped links in the middle so that one piece remains connected to the flapper and the other one to the handle. In this case, you’ll need to reconnect the 2 pieces by slipping the middle links together.

   Importantly, ensure that you bend the links properly so that they won’t pull apart again. However, it’s also advisable to replace the entire chain if it’s rusty

3. Inadequate Water In The Cistern

   Insufficient water in the toilet tank might also be the reason why your toilet won’t flush. If there’s no enough water in the tank, even the best flushers such as the Toto CST454CEFG-01 Drake II toilet won’t create enough flush to send everything down the drain and no one wants a toilet hard to flush.

   Most toilet cisterns have the manufacturer’s designated water level mark usually about an inch below the top of the overflow tube.

   Low water level may be as a result of a water valve that has been accidentally turned OFF. To fix this, turn it ON and monitor to see if the water level will rise to the correct level.

   If the water is trickling in but does not reach the required mark:

   1. Inspect to see if there are some debris that cause the float mechanism to shut off the water valve prematurely
   2. Use needle-hole pliers to loosen a small nut that regulates how high the float rises. This nut should be a few inches from where the water valve is (inside the tank) along the arm of the float.

4. Clogged Rims (The Lazy Flush)

   When you pull down the flushing handle, water is forced down into the toilet bowl through small angled inlet holes found under the rim. Sometimes, these rim jets become clogged by mineral deposits over time and that’s one of the reasons why your toilet doesn’t flush all the way.

   To inspect whether the rims are clogged:

   1. You might stick your head inside the bowl or simply use a small mirror.
   2. Depending on how bad the buildup is, you could use an ice pick, Bobbie pin, or an old paring knife to chip out the mineral deposits then flush.
   3. Another option here is to use white vinegar. To do this, flush all the water in the toilet cistern and add a few cups of white vinegar. Pull the handle slowly so that the vinegar trickles down the system and leave it to stand overnight. Given enough time, the vinegar should dissolve the mineral deposits like a charm.

Call Your Plumber

These are the most common culprits in toilets that won’t flush. Toto’s Product FAQs section also has a few more reasons why your toilet won’t flush completely or has weak flushes and how to solve them.
If none of them works, be glad that you tried your best to fix the problem and call your local plumber.

Worth mentioning, a toilet that needs maintenance every other day is a sign that you need to replace the entire system. If this is the case, you might find our best toilet buying guide really helpful if you don’t know what to check out for when buying a new commode.

Dan is the editor in chief and founder of this site, after running into troubles with his own old toilet a while ago. Discussing toilets is not your everyday topic, so let’s talk toilets today.