Bathroom Renovation Plumbing Costs in Melbourne
Plumbing is the part of a bathroom renovation most people underestimate. It sits behind the wall and under the slab, so it doesn’t show up in the mood board — but in a Melbourne home it typically accounts for roughly 15–25% of the total project cost, and it’s the single biggest source of mid-job surprises.
Underquoting plumbing doesn’t save money. It defers it. Hidden leaks, rotting subfloors and failed waterproofing all trace back to plumbing that was scoped too thin at the start.
This guide covers plumbing-only costs so you can read a quote properly. Everything else — demolition, tiling, cabinetry, waterproofing, electrical — sits outside these figures.
A note before you read on: we don’t take plumbing-only work. House Sanctuary Builders scopes and prices plumbing as part of a complete bathroom renovation. If you need a plumber for a standalone repair or fixture swap, you want a licensed plumber, not a builder.
What plumbing work actually includes
A properly scoped bathroom plumbing package covers:
- Removal and replacement of existing fixtures and pipework where required
- Drainage relocation if required — toilet, vanity, shower, bath, floor waste
- Water supply rerouting, with hot and cold tail-outs set at the correct heights
- Installation of isolation valves
- Fit-off of new tapware, showerheads, toilets, baths and vanities
- Gas connection, if the gas hot water unit is being relocated
- Pressure testing and compliance certification
That last line matters. Compliance certification is a legal requirement in Victoria, and a quote that doesn’t mention it is a quote you should ask questions about.
What plumbing costs
Figures below are plumbing scope only, current as of August 2026.
| Scope of work | Cost (AUD) | Notes |
|---|---|---|
| En-suite, existing layout | $3,000 – $5,500 | Direct replacement, no relocation |
| Standard bathroom, new layout | $5,000 – $10,000 | Moving toilet, shower, bath, vanity |
| Bathroom and laundry combined | $8,500 – $14,500 | Includes new floor waste |
| Add-ons | ||
| Concrete floor cutting | +$1,000 – $1,500 | Required for most drainage relocation on slab |
| Cast-iron stack replacement | +$1,000 – $3,000 | Common in pre-1970s homes |
| In-wall toilet cistern | +$500 – $1,000 | Per toilet |
| Contingency | +10% | For what the walls hide |
The contingency line isn’t padding. Once the walls are open, the condition of what’s behind them is no longer a guess — and in older Melbourne housing stock it’s rarely good news.
Four things that push the number up
1. Concrete floor works
Moving a toilet even 300mm on a slab means cutting the concrete, laying new pipe and making good. There’s no cheap version of this — it’s why “just shifting the toilet a bit” is never a small change.
2. Cast-iron stack replacement
Standard in pre-1970s homes across the inner south-east. If the stack has corroded, replacing it with PVC is the only real fix, and it’s a full-height job rather than a bathroom-level one. We see this regularly in our Kew, Hawthorn and Brighton projects.
3. Hot water capacity
A new rain shower head moves considerably more water than the fixture it replaced. An older unit at 150 litres or less will run cold halfway through a shower. The fixture upgrade forces the system upgrade, and most people don’t find out until the tiles are already on.
4. In-wall cistern
The cistern sits inside a stud wall or purpose-built bulkhead, leaving only the pan and flush plate visible. It buys back floor space and looks considerably cleaner. It also requires the wall to be built to accommodate it, which is a framing decision made early — not a fixture choice made late. Worth reading alongside our guide on choosing the right toilet bowl.
Where plumbing sits in your total budget
Plumbing on its own tells you very little. A $5,000 plumbing figure means one thing in a $36,000 renovation and something quite different in a $60,000 one.
When you’re comparing quotes, the questions that actually matter are:
- Is compliance certification included, or billed later?
- Who carries the cost if the stack turns out to be corroded?
- Is the hot water unit priced in, or listed as a provisional sum?
We price bathroom renovations as a single scope with the plumbing already inside it, so the number you sign is the number you pay. You can see how we work through our renovation process, and browse completed work in our project gallery.
Frequently asked questions
How much does it cost to move a toilet in a bathroom renovation? On a concrete slab, budget $1000 to $1,500 for the concrete cutting and drainage work alone, on top of the base plumbing scope. On a timber subfloor it’s usually less, because there’s no slab to cut.
What percentage of a bathroom renovation is plumbing? In a Melbourne bathroom renovation, plumbing typically accounts for roughly 15–25% of total project cost, depending on whether the layout changes and what condition the existing pipework is in.
Do I need a separate plumber, or does the builder arrange it? On a full renovation the builder arranges and coordinates the licensed plumber as part of the scope. Engaging trades separately means you carry the coordination risk and the sequencing delays yourself.
Why is my plumbing quote so much higher than my neighbour’s? Usually the layout. Keeping fixtures where they are is dramatically cheaper than relocating them. Age of the home is the second factor — cast-iron stacks and undersized hot water units are common in older stock and don’t appear in a walkthrough quote.
Get your bathroom renovation scoped properly
House Sanctuary Builders has been renovating bathrooms across Melbourne for over a decade, with a 4.9 star rating from 143+ reviews. We scope plumbing properly at the quoting stage so it doesn’t become a variation later.
Request a quote or call 0406 309 088.
