Short answer
A licensed plumber. It is almost always the inlet valve or the outlet seal in the cistern, both routine replacements — and because the attendance is the bulk of the cost, get every other dripping tap and slow leak in the house done on the same visit.
What to do before anyone arrives
- Prove it is the toilet: put a few drops of food colouring in the cistern, wait twenty minutes without flushing, and look in the bowl. Colour in the bowl means the outlet seal is passing.
- Read the water meter with everything in the house turned off, wait ten minutes, read it again. That tells you whether you also have a second leak you have not found.
- Take the cistern lid off and look for the brand stamped inside. Parts are brand-specific and it saves a return trip.
What to ask when you book
- Do you carry inlet and outlet valves for this brand on the van?
- Can you do the other small leaks while you're here, and what does that add?
- If the cistern is an obsolete model, what are my options besides replacing the pan?
What changes the price
No dollar figures here: this directory holds no price data and an invented range is worse than none. What follows is what makes one of these jobs cost more than the same job next door, which is the part you can actually use when comparing quotes.
- Whether parts are current or obsolete for that cistern.
- Concealed cisterns in a wall, which are a different job from a close-coupled one.
- Whether the seat and the pan connection have also perished, which is common on the same age of fitting.
What you can do yourself
Is this licensed work?
Plumbing is licensed work. Some states treat replacing a cistern's internal parts as minor maintenance a householder may do; the exemptions differ, so check your regulator rather than assuming.
There is no national register. Search the licence number with the regulator for the state the work is happening in.
- NSWNSW Fair Tradingbuilders, electricians, plumbers and specialist trades
- VICBuilding and Plumbing Commission, and Energy Safe Victoria for electricalbuilding practitioners and plumbers; electricians are Energy Safe Victoria
- QLDQueensland Building and Construction Commission (QBCC)building and most trade contractor licences
- WABuilding and Energybuilders, electricians, plumbers and gas fitters
- SAConsumer and Business Servicesbuilding work contractors and supervisors
- TASConsumer, Building and Occupational Services (CBOS)building and occupational licences
- ACTAccess Canberraconstruction occupations licensing
- NTNT Government building practitioner registrationbuilding practitioners and electrical workers
Licensing thresholds and certificate requirements differ by state and change with amending regulation, so this page describes the mechanism rather than quoting a figure. The regulator’s own page is the current answer.
Common questions
- Who should I hire for a toilet that keeps running
- A licensed plumber. It is almost always the inlet valve or the outlet seal in the cistern, both routine replacements — and because the attendance is the bulk of the cost, get every other dripping tap and slow leak in the house done on the same visit.
- How much water does a running toilet waste?
- A continuously passing outlet seal runs day and night at a rate you would notice immediately if it came out of a tap. The bill is the evidence; the food-colouring test is the proof of which toilet it is if you have more than one.
Find a Plumber near you
3,553 plumbers in this directory, ranked on published evidence rather than on advertising.
Who to hire for
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- Who to hire for a blocked toiletA licensed plumber. Try a proper toilet plunger first — the flanged kind, not the flat cup for sinks — and sto…
- Who to hire for low water pressureA licensed plumber — but first work out whether it is one outlet or the whole house, because one outlet is usu…
- Who to hire for a blocked drainA licensed plumber — specifically one who owns a drain machine or a high-pressure water jetter, which not ever…
General information about who does what, not advice about your specific job. Licensing, consumer law and council rules differ by state and change; the regulator for your state is the current source. More guides to hiring a tradesperson.