[SOLVED] Toilet Leaks When Flushed: How to Stop the Leak?

A leaking toilet can be very frustrating, especially if you have no idea of the source of the leak.

It doesn’t only make your toilet messy and unsightly but can also raise your water bill significantly.

toilet leaks when flushed

Most times, a toilet that leaks when flushed requires a simple fix and rarely needs a professional plumber.

If you have a toilet that leaks when flushed, this post is for you.

I will guide you on how to diagnose and quickly fix the leaky toilet without any expensive repair. Read on.

Why Is My Toilet Leaking When Flushed?

Your toilet will leak when flushed due to one or more of the following reasons:

  • Loosened or worn-out toilet T bolts.
  • Loosened or worn-out toilet tank bolts.
  • Damaged wax ring (rubber gasket seal).
  • Worn-out or damaged spud washer (if your toilet tank is not a single unit with the bowl).

You would need to give some of your time to properly investigate where exactly is your toilet leaking.

Is the toilet leaking in-between the toilet tank and bowl when you flush it? If yes, then the spud/sponge washer is damaged. Your toilet will also leak in-between the toilet tank and bowl when flushed due to loose tank bolts.

For a leaky toilet base, either the toilet mounting bolts are bad or the wax ring (rubber gasket seal) is damaged.

How to Fix Toilet Leaks When Flushed?

If the toilet leaks are in-between the toilet tank and the bowl, replace the spud washer and/or worn-out tank bolts.

If the toilet leaks are at the toilet base, replacing the toilet T bolts and the wax ring will fix this.

The first thing to do is to stop using the leaky toilet and avoid flushing it. It’s fine if you’ve already pinpointed where the toilet is leaking. But using the leaky toilet will only worsen the case or cause more damage.

Now that you know what to fix, you can hire an expert plumber to fix the toilet problem. This will save time and stress, and alleviate your worries.

However, if you’re a happy DIYer, you can quickly make the repairs and fix your toilet problems using this guide:

What You Would Need?

If you’re handling the repairs yourself, you would need the following tools and materials:

  • A putty knife
  • An adjustable wrench
  • A pair of latex gloves
  • A flathead screwdriver
  • A sponge
  • An empty bucket
  • A hacksaw blade and/or mini-hacksaw
  • A towel or rag
  • A new wax ring (or rubber seal)
  • A new spud washer
  • Replacement tank bolts, nuts, and washers
  • Replacement toilet bolts, nuts, and washers

We recommend that you purchase the last four materials after removing the old ones. This will enable you to get the exact size and model for your toilet.

With the materials in place, follow these steps carefully and sequentially to fix your leaky toilet.

Step 1: Check the Tank Bolt and Toilet T Bolts

The first step to fixing your leaky toilet is to check both the tank bolt and toilet T bolts. This will save you so much time and effort.

The tank bolts secure the toilet tank tightly on the toilet bowl. If they get worn out or loosen, they can misadjust the spud washer.

This will cause the toilet to leak water when flushed. You don’t have to be concerned about this if your toilet bowl and tank are a single unit.

The toilet T bolts secure the toilet bowl tightly on the toilet flange. If they are loose or worn out, they can break off the wax ring seal/rubber seal. This will cause the toilet to leak at the base.

Turn off the supply of water to the tank. You should see the control valve behind the toilet bowl.

Depending on the type of control valve you have, turn it completely clockwise or pull it to shut the supply.

Remove the water in the tank by giving the toilet one last flush. Hold down the flush lever (or flush button) to remove all the water from the tank into the toilet bowl. Open the tank cover and keep it somewhere safe.

If you use a toilet with a flush button, be careful to disconnect a flush button duct. Remove any water remaining in the tank with a sponge until the tank is empty.

Also, mop off any water on the toilet floor with a rag to avoid slipping or falling.

Checking the Toilet Tank Bolt

Look inside your toilet tank, you should see two (or three) bolt heads at the bottom.

Using a flathead screwdriver, turn these bolts until they feel tight. If the bolts are turning endlessly, hold the complementing nuts under the toilet tank with a wench and turn again.

If the bolts turn tight, you’ve fixed the problem of loose tank bolts. Otherwise, the tank bolts are rusted or worn out and need a replacement.

You’ll learn how to replace the worn-out tank bolt in the next step.

Checking the Toilet T Bolts aka Mounting Bolts

Look at the base of the toilet bowl, you should see two inverted bolts – one on either side.

Most times, these bolts have plastic caps covering them for aesthetic purposes.

Remove the plastic caps and turn the nuts with a wrench or pliers until they feel tight. If the nuts turn tightly, you’ve fixed the problem of loosed toilet T bolts.

If the nuts turn endlessly or won’t turn at all, the toilet T bolts are bad and need a replacement. You’ll learn how to replace bad toilet T bolts in the next step.

Step 2: Check the Tank-To-Bowl Gasket/Spud Washer

The spud washer seals the connection in-between the toilet tank and the bowl. If it’s bad, your toilet will leak in-between the toilet tank and the bowl. If your toilet is a single unit, skip this step.

Loosen the tank bolts to disconnect the tank from the toilet bowl. Using both hands, gently lift the tank off the toilet bowl.

Be careful to avoid damaging the flush valve in the tank. Place the tank on its side in a safe place.

Look under the toilet tank, some tanks do have nuts that hold the tank bolts in place. Loosen these nuts to completely remove the bolts.

Now, check if the spud washer is bad or worn out. You may also need to loosen the locknut to check the O-ring, washers, discharge tube, and flush valve shank.

If the spud washer is bad, get a replacement for it.

Better still, get a replacement for the entire gasket unit if other parts are bad too.

Check if there are dirt, debris, and/or mineral deposits around the hole – inside and outside.

Take them off before inserting the new tank-to-bowl gasket unit.

Make sure that the entire unit fits the flapper valve nut and sits well before holding it firmly with the locknut. Tighten the locknut gently with a wrench to provide a leak-proof seal.

Finally, cover the outer end of the discharge tube with the spud washer. The damaged tank-to-bowl gasket is now fixed and the tank is set to be reconnected to the toilet bowl.

Watch this video for more understanding of how to replace a bad spud washer –

Step 3: Check the Wax Ring

The wax ring closes the connection in-between the toilet bowl and the drain pipe. If the ring is bad, especially when the toilet bolts are also bad, your toilet will leak at the base.

Remove the plastic caps covering the T bolts and loosen the nuts to disconnect the bowl.

Turn the toilet bowl slightly to the left and right to free it from the wax ring seal. Your toilet bowl is now disconnected.

You may need an extra hand for this. Gently lift the toilet bowl off the drain pipe and place it in a safe place.

You may cover the drain pipe to prevent sewer gases from escaping into your toilet.

Check the wax ring if it’s bad and needs a replacement (some toilets use a rubber seal instead of a wax ring). Before replacing the wax ring (rubber seal), check the toilet flange and remove the damaged toilet T nuts.

Slide the damaged T bolts out from the grooves on the toilet flange. Gently scrape off the remains of old wax on the toilet bowl and flange.

If the flange feels loose, tighten it and if it’s broken, replace it. Now, it’s time to replace the damaged T bolts with new ones of the same size and length.

Slide the new T bolts into the flange through the groove until they lock-in. Place the new wax ring around the drain pipe.

The narrow end goes into the drain pipe while the waxy head sticks around the discharge opening on the bowl.

If the toilet uses a rubber gasket seal, set the seal on the flange to fit the openings for the T bolts.  

If you had covered the drain pipe earlier, remove the covering carefully and place the bowl gently on the flange.

Make sure that the toilet bowl sits rightly on the bolts. Press down the bowl gently to compress the wax ring and form a leak-proof seal.

Place the washers and nuts on the bolts and tighten them with your hand. Tighten the nuts further with an adjustable wrench.

However, be careful while doing this as over-tightening can damage the bowl. Once the bowl is stable and doesn’t wobble, you should stop tightening the nuts.

Cover the ends of the bolts with their plastic caps. If the new bolts seem longer to allow the caps, trim them with a hacksaw.

Watch this video for more understanding of how to replace a bad wax ring –

Step 4: Reconnect the Toilet Tank

You’ve successfully replaced the damaged wax ring (rubber gasket seal) and T bolts, and have reconnected your toilet bowl. Now, it’s time to replace the damaged tank bolts with new ones and reconnect the toilet tank.

Some tanks require that you first tighten the tank bolts on them before placing them on the bowl.

If this sounds like yours, insert the new bolts from inside the toilet tank. Place the nut at the end of the bolts and tighten them on the tank.

Place the toilet tank carefully on the bowl. Let the fixed bolts go into their openings on the tank or let the openings for the bolts align.

Ensure that the spud washer or O-ring seal fits perfectly on the matching opening on the bowl.

Place the nuts on the bolts under the bowl and tighten them gently using your hand. Further, tighten the nuts with an adjustable wrench until the tank is stable and firm on the bowl.

Be careful, over-tightening the nuts can crack your toilet bowl. Once the tank is secured and stable on the bowl, place the lid back on the tank.

Step 5: Reconnect the Water Supply

Finally, it’s time to test whether your toilet is truly fixed.

Reconnect the rubber hose by tightening the plastic screw on it to the fill valve. Turn on the control valve and allow water to enter the toilet tank.

Do this by turning the control valve completely anticlockwise or pushing the push/pull valve to turn on the water supply.

Flush your toilet about three times and check if there is any leak at the toilet base or spud washer.

If you still notice any leaks at these spots, you may need to call on a professional plumber to fix this.

Otherwise, you have successfully fixed your toilet that was leaking when flushed.


Fixing your toilet that leaks when you flush it is a simple DIY project.

With the straightforward guide above you should be able to determine and fix the cause of your leaky toilet.

However, if you were unsuccessful at fixing it, don’t hesitate to call on an expert plumber to assist you with this.

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