Easy Guide: Fix A Toilet Not Flushing But Not Clogged

A gravity-style toilet plumbing system operates a toilet flush by dumping a lot of water into the bowl quickly in order to create a strong flush. The act of dumping a lot of water into the bowl creates a siphon effect that gets rid of the waste.

When the flush valve, rim holes, and siphon jets are fully open, the water will flow from the tank to the bowl as quickly as possible to allow the siphon to take effect.

For this to all happen effectively, you’ll need to make sure the tank is set to have enough water in it to get the job done right and all the pathways from tank to bowl are clear and ready to go.

In this blog post, we’ll go through some of the common reasons that your non-clogged toilet won’t flush properly and what to do about it. It might not be time to buy that toilet auger from your local hardware store just yet, there may be some other issues at play. Let’s discuss some of the common culprits.

In Summary

The possible reasons why toilets don’t flush all the way can be because of:

  • clogged siphon jets and little holes around the rim of the bowl,
  • or the level of water in the tank is too low.

You might also have:

  • a bent or warped flush valve,
  • slack lift chain,
  • or an improperly designed drain pipe causing the problem.

If you have hard water, it’s a good chance you’re dealing with clogged siphon jets and rim holes. Calcium deposits, otherwise known as limescale, are what is to blame when this happens.

If your toilet is new and it won’t flush properly, you most likely have a poorly designed drainpipe. To allow the waste to be emptied from the bowl easily with gravity, a toilet drain pipe needs to slope downward.

The toilet flapper seals over the flush valve at the bottom of the tank. This one’s connected to the lift chain, which then connects to the flush handle via the handle arm.

In order to prevent the toilet flapper from not fully closing, the lift chain should not be too loose, otherwise less water will enter the tank than intended. As a result, the toilet will not flush adequately.

When a toilet flapper is bent or warped, water slowly seeps underneath it, entering the bowl and reducing the flushing water, not to mention the massive waste of water over time. In this case, the toilet will not flush fully when you need it to because the tank is never full.

Let’s drill into more detail about why your toilet doesn’t flush all the way even though it isn’t clogged.

Siphon Jet And Rim Holes: Are They Clogged?

The first thing to note here is that not all toilet designs have a siphon jet. We’ll describe this common issue and what can happen in toilets with and without siphon jets. But first, let’s get a quick description of a siphon jet.

What Is a Siphon Jet?

At the bottom of the toilet bowl, there is a hole directly opposite the drain opening known as a siphon jet. By pushing some of the water down the toilet’s P-trap, it helps create a stronger siphon, which is what helps flush the toilet.

Common to all designs, pulling down the toilet flush handle releases the flapper from the opening where the flush valve is located, allowing water to flow into the bowl in a fast and vigorous event. 

A combination of a siphon jet and rim holes, or just rim holes direct the water into the bowl to achieve this.

The Lowdown On Rim Holes

Bowl rims contain tiny holes surrounding the rim. In toilets that have siphon jets, the rim holes are just to rinse the bowl, but in toilets that don’t have siphon jets, the holes have the 100% job to flush all the waste away.

You can get a good look at these rim jets if you hold a mirror just under the rim of the toilet bowl where you can clearly see them.

If you don’t see these rim jets, it will be because you have one of the more modern toilets with either the double-cyclone flushing systems or Tornado types. With these, there are only 2 holes built into the bowl rim. They can also get clogged.

A clog event caused by mineral deposits can either be complete or partial and can affect the rim holes and/or the siphon jet if your toilet has one. This will cause the situation of a slow flushing toilet where your toilet won’t flush completely, even though there is no blockage further down the line.

It occurs because clogged rim holes and a siphon jet means that no water or very little of it enters the bowl from the tank during the flushing cycle. A fully successful flush (and don’t we all want that!) requires a large volume of water to be dumped inside the bowl very fast to generate that decent flush.

The good news is that this problem is pretty straightforward to fix, and it is much less icky than some other toilet blockage problems – but we will leave those to your imagination for the purposes of this discussion. So all you have to do is unclog the siphon jets and holes.

Unclogging Rim Jet Holes And A Siphon Jet: Quick How-To Guide

To get this done the best way, this is what you will need:

  • Gloves that are waterproof (rubber gloves are best)
  • White vinegar
  • Wrench (L-shaped – small)
  • Some baking soda (optional but ideal)
  • A short piece of thin hose (optional)

Firstly, if your toilet has a siphon jet, proceed as follows:

  • Locate the siphon jet at the bottom of the bowl
  • Put the gloves on (this is a bit obvious but we’re covering all bases here if you want to avoid toilet water on your bare skin)
  • Using a combination of your finger and the thin hose pushed in and out of the siphon jet, physically break loose as much of the mineral buildup as you can.
  • Flush the toilet to see if the power of the flush has increased significantly. If it has, then good job. You’ve identified the problem and are well on the way to fixing it.
  • It is still important to get rid of all the mineral deposits, so continue on.

Do the following steps regardless if you have a toilet with a siphon jet or not:

  • You need to remove as much water as possible from the toilet bowl. This can be done with a toilet plunger or alternatively, you can saturate an old rag or towel with the toilet bowl water to completely remove it and have the bowl empty.
  • Carefully take the toilet tank lid off and if it is porcelain, set it aside carefully where it won’t get broken if knocked etc.
  • Pour vinegar (about two cups) carefully down the overflow tube situated inside the toilet tank. This way, the acid solution will go directly into the bowl via siphon jet (if present) and rim holes and do the work of breaking down the calcium deposits.
  • To speed things up, an optional step is you can add some baking soda to the mix to get to the mineral scale breakdown process happening more quickly.

Vinegar will dissolve calcium in the siphon jet and rim holes, thus opening them fully. Avoid using Muriatic acid instead of regular old white vinegar it is not good for septic systems (if you have one) and can be harsh on the toilet finish, not to mention the environment.

Now it’s a bit of a waiting game. Wait at least 3 to 4 hours for the vinegar to do its work. Then:

  • Using an Allen wrench or something similar, make sure that each rim hole is clear of any deposits.
  • Check to see if the toilet is strongly flushing.

So that’s what you need to do to clear a toilet’s rim and siphon jets. To prevent the whole problem from coming back in the future, every six months or so, pour a little vinegar or detergent down the internal toilet tank overflow tube to keep things clear.

How To Diagnose A Low Water Level In The Toilet Tank

The water supply in the toilet tank should come to about half an inch below the top of the overflow tube. If it comes any higher than that, water will come down through the overflow tube, resulting in the toilet leaking water into the bowl, even when not being flushed.

Too little water in the toilet tank can prevent it from generating the needed strong siphon action, resulting in it not flushing all the way, even if it is not clogged.

It is necessary to adjust the toilet float in order to adjust the level of water inside the toilet tank. By moving up and down the tank in response to the level of water, toilet floats control the opening and closing of the fill valve.

This is how to adjust the tank water level in a toilet:

  • Check if you have an older float ball arrangement (ballcock) or float cup (in newer toilets) . A ballcock features a balloon-like ball attached by an arm to the fill valve. A float cup design is much smaller and is connected to the fill valve along its vertical body.
  • With a float ball type, the float lever/arm must be connected to the fill valve. A small screw will be visible. The water level should be about half an inch below the top of the overflow tube after turning the screw clockwise.
  • On a float cup, you should see a long plastic screw along the fill valve. By turning the screw clockwise, you can raise the water level inside the toilet tank using your bare hands or a screwdriver.

Flush the toilet again and see if it flushes strongly after adding new water to the tank. If you’ve adjusted it to make the height of the water too much, water will be exiting through the overflow tube when the toilet is not in use, resulting in a large loss of water over time – so be careful not to do this.

Check For A Warped Or Bent Toilet Flapper

Although a toilet flapper valve usually last a long time, they can bend or warp, meaning they will no longer create the tight seal on top of the flush valve as intended. The tank gradually loses water to the bowl as it leaks out resulting in a constantly running toilet.

The flapper can also develop this problem due to mineral deposits underneath it. This situation will result in a weak flush due to insufficient water in the tank.

When this occurs, the toilet tank will refill automatically whenever level of water drops below the kick-in level of the refill valve. This is known as ghost flushing.

The only way to fix a warped or bent toilet flapper is to replace it with a new flapper unless there are mineral deposits underneath which can be removed using the white vinegar method.

It is inexpensive and easy to replace a toilet flapper if you do it yourself.

Check For A Slack Flapper Chain

There must not be much slack on a toilet flapper chain. You need 1.5 inches of slack in your toilet lift chain for a decent flush. This means less water will flow to the bowl if it is too slack.

Another issue with a lift chain is that it might become detached from the lever or flapper. Occasionally, it can even become hooked to another part of the toilet tank, making it impossible for it to move freely.

The toilet lift chain rarely fails, but when it does, it’s easy to miss it as the culprit since you rarely even think about it as a possibility. So it is important to check off that the toilet lift chain is working properly.

Check For A Drainpipe That Is Poorly Designed

If you have a new toilet, so you know it is not one of the issues we’ve already discussed, unfortunately, this could be your problem. 

If your newish toilet had good flush power in the past and just deteriorated recently then this situation is possible.

The toilet P-trap assists in creating a siphon in the toilet to quickly remove the waste. Another requirement to get this to work correctly is a downward sloping pipe that connects to the main sewer line or septic tank line needs to be installed after the P-trap.

Unfortunately, you cannot solve this problem by yourself – it is where a professional plumber comes into the picture. The cost of troubleshooting and repairing it may be quite high so steady yourself for the possible quote amount.

It basically works the same way for a toilet that isn’t clogged but won’t flush.


So there you have it. There can be a few different reasons why a toilet won’t flush properly, even when it is not obviously clogged by a single ‘event’. Hopefully, it is one of the reasons that you can rectify yourself as an easy fix and most importantly, a DIY fix. Happy diagnosing and fixing!

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