How to Repair Leaks on the Outside of the Toilet Tank

How to Repair Leaks on the Outside of the Toilet Tank


Leaks that appear on the outside of the toilet tank are important to consider, as they can cause serious damage.

If you find such a leak, take quick action before things get dirty. Let’s delay no further; this post will tell you how to do it.

Causes of leaks on the outside of the toilet tank

There are two main causes of leaks on the outside of the toilet tank:

  • Wear and tear of the gasket on the back of the bowl under the tank;
  • Loose screws secure the tank or bowl.

1. Re-seal the toilet bowl and tank

If you find that the water leakage is coming from the junction between the toilet bowl and the cistern, it is necessary to replace the gasket located at this location, but perhaps also the screws securing the cistern and the flushing mechanism.

During this disassembly, the old flushing mechanism should be replaced, and a more water-efficient model should be chosen. A two-speed model, for example, uses only 3 liters of water per flush instead of 8 to 10 liters for the old flush mechanisms. There are very practical kits on the market that can be adapted to all kinds of toilet models.

Dismantle the toilet tank

Turn off the water supply and flush the toilet to empty the tank.

Loosen the nut on the tank’s water supply valve using a wrench.

Loosen the nuts on the tank mounting screws using a pair of pliers.

Remove the tank from the bowl and lay it flat on a towel.

Remove the old foam gasket and clean the edges of the hole to remove lime deposits.

Reassemble the tank

If you are changing the flush mechanism:

Insert the new flush mechanism into the tank from the inside.

Fit the PVC nut onto the thread of the mechanism and screw it on using the special toilet wrench usually included in the flush kit.

Place the new foam gasket around the PVC nut.

Replace the tank.

Insert its screws in their places, with their seals, then screw their nuts. Tighten the nuts of the screws one after the other to compress the gasket evenly.

Next, connect the valve to the side of the tank, tighten its nut with a wrench, and then fill the tank.

Adjust the water level and the float.

Replace the cover and flush control.

2. Fix leaks in the drain

The junction between the toilet bowl and the flush pipe can leak. A leak at this point is very annoying because the water that flows out is dirty. It is, therefore, necessary to intervene quickly.

To fix this type of leak, it is necessary to remove the toilet bowl.

Before you start:

Turn off the water supply to the tank and flush the toilet to empty the tank.

Empty the water in the toilet trap with a sponge or ladle. Wear gloves for this operation.

Disassemble the toilet bowl

Using a wrench, unscrew the nut on the tank’s supply valve and pull the valve away.

Unscrew the screws that secure the bowl to the floor. If oxidation has blocked them, cut them out by passing a saw blade between the floor and the bowl.

Unscrew the connecting sleeve and remove the bowl. Wedge the base of the bowl and lean the tank against a wall to prevent the toilet from tipping over and being damaged.

Replace the flush sleeve gasket

Using a hacksaw, cut off the flush collar clamp.

Remove the old gasket.

Thread the new gasket onto the vent sleeve (leave it on the vent pipe, do not attach it yet).

Place the new gasket in the groove provided, then pull the ring forward to lock and secure the gasket.

Note: if silicone or PVC glue is used, it will be necessary to wait 24 hours (drying time) before using the toilet.

If the sleeve or the drain elbow is too damaged

If you notice that the liner and the drain elbow are damaged or too old, take the opportunity to replace them. Proceed as described below.

Using a hacksaw, cut the drain pipe flush with the sleeve.

Fit and glue a new sleeve of the same diameter.

Coat the sleeve with silicone grease.

Insert the outlet of the bowl into the joint of the drain sleeve.

Reassemble the bowl

Position the cuvette so that the outlet is in line with the sleeve, so that the point is well positioned.

Carefully replace the bowl in its place.

Replace the tank and tighten the nuts on the tank mounting screws with a wrench.

Connect the water inlet valve to the tank by tightening its nut with a wrench. If the bowl is correctly positioned, there will be no problem attaching the valve.

Screw in the screws securing the bowl.

Open the water supply valve to fill the tank.

Replace the cover and attach the flush control.

3. If water stagnates under the toilet bowl

The junction between the toilet bowl and the floor can be the place where all the moisture from leaks and wash water seepage is concentrated.

If water is trapped under the toilet bowl, you must remove it to clean the floor. See the previous steps for disassembly and reassembly.

After reassembling the toilet bowl, it is recommended to make a silicone seal on the floor around the base of the bowl to prevent water from seeping underneath.

Important: do not make a silicone seal without cleaning the underside of the toilet bowl.

4. Check the installation

Flush the toilet and check that:

the water stops flowing into the bowl when you stop flushing;

the space between the bowl and the tank is not wet;

the flush pipe is not leaking.

If leaks persist, repeat the process step by step.

Materials to repair leaks on the outside of the toilet tank

Drain sleeve clamp

Adjustable wrench

Silicone grease

Drain sleeve gasket

Toilet foam gasket

PVC sleeve

Flush mechanism

Multi-socket pliers

Metal saw


How to Repair Leaks on the Outside of the Toilet Tank

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