Why Is My Toilet Leaking? Common Causes and Quick Fixes

A toilet leak usually starts quietly. Maybe you hear a faint hiss every now and then. Maybe the cistern keeps refilling for no reason.  It’s one of those things you don’t pay attention to until suddenly you’re wondering why your water bill went up, or why the floor around the toilet feels a bit damp. It’s the same story with dripping taps. That constant tik…tik…tik can drive you mad, but it’s also literally money dripping away down the drain. The good news? Most of this is fixable. And not every toilet leak needs a full bathroom takeover. Let’s break down what usually goes wrong and how to tell if you can DIY it, or if it’s time to call a plumber.

Signs Your Toilet Is Actually Leaking

Some leaks are obvious, such as water around the base, damp patches, and puddles.
Others are sneaky.

Look out for:

• The cistern keeps topping up / refilling by itself
  
• hissing noise from the tank
  
• damp or discoloured flooring
  
• water sitting around the base
  
• sudden jump in water bill
  

And here’s a quick little test:

Add a few drops of food colouring into the cistern and leave it for 15 minutes (don’t flush!). If the colour shows up in the bowl, water is leaking through.

The Most Common Reasons Toilets Leak

Toilets are pretty simple machines. A few small parts working together. One tired or worn-out piece and you’ve got a leak.

1) Flapper Worn Out

The flapper is the rubber piece at the bottom of the cistern. If it doesn’t seal properly, water constantly escapes into the bowl.

Quick try: turn off the water, lift the cistern lid, check the flapper. If it looks warped or stiff, replace it. They’re cheap.

2) Faulty Fill Valve

This is what controls how much water goes into the tank. If it’s faulty, water rises too high and spills into the overflow tube.

Quick try: Adjust the float or replace the valve.

3) Loose Tank Bolts

Water between the tank + bowl usually means the bolts (and rubber washers) are no longer sealing properly.

Quick try: gently tighten the bolts, not too hard (porcelain cracks easily).

4) Wax Seal Gone at the Base

If every flush leaves a little puddle at the base, the wax ring underneath is gone.

Reality: This one usually needs a plumber; the toilet needs to come off completely.

5) Cracked Porcelain

Small hairline cracks can create constant, slow leaks.

If the crack is above the water line, epoxy sometimes buys you time.

Below the water line: the toilet is done, time for a replacement.

6) Condensation / Sweating

Sometimes it’s not a leak at all, just humidity + cold tank water.

Try: bathroom fan/tank insulation kit.

Can You Fix a Toilet Leak Yourself?

Sometimes yes. Replacing a flapper? → easy. Adjusting the fill valve? → doable.

Leaks at the base? Cracks? Internal damage?

This is where DIY gets risky because one wrong twist can break a seal or fitting… and then the “small leak” becomes “major panic”.

We handle these all the time, so if you’re unsure, call us in before it becomes flooring damage.

And Those Leaking Taps…

A single tap that drips all day long, that’s thousands of litres wasted a year. Most of the time, it’s worn washers, O-rings or corrosion inside the tap body. If you want to try it yourself, shut off the water, open the handle, and check the washer/O-ring. If it’s worn flat or brittle, replace it. If it still leaks after that? Probably corrosion. That’s a plumber’s job.

How to Stop Leaks from Happening Again

• Check around taps + toilet base every now and then
  
• Replace rubber seals before they totally fail
  
• don’t “tighten taps” like you’re turning off a fire hydrant
  
• occasionally lift the cistern lid and look inside
  
• Watch your home’s water pressure; too high = seals die early 

Small checks → big savings.

Why People in the Shire Call South East Plumbing

Locals around Engadine, Sutherland Shire, St George, Illawarra and Wollongong call us because we keep it simple, offer honest pricing, clear explanations, and work done right the first time.

We’re licensed. We’re insured. And we treat every home like a neighbour’s home. Whether it’s a worn washer or a leaking toilet base, we’ve fixed thousands of them.

Leaking toilets and taps are common, and they’re usually fixable fast if you catch them early. And if you’re unsure what’s causing the leak, don’t guess. A quick inspection now can prevent a bigger repair later.

Call 0414 651 351 or book online,  and we’ll sort it out.