Plumbing is rarely the biggest line in a renovation budget, but it is the one that most often blows out, because decisions made casually at the design stage (let's move the toilet to that wall) carry price tags nobody mentioned at the time.
This guide explains how renovation plumbing is staged and priced, what moving each fixture actually involves, and the design decisions that keep the plumbing bill sane.
Rough-in and fit-off: why the plumber comes twice
Renovation plumbing happens in two stages. The rough-in brings water and drainage pipes to each fixture position while walls and floors are open. The fit-off happens after tiling and cabinetry, when taps, toilets, basins and the shower are connected and commissioned.
Both visits are quoted together but scheduled weeks apart, which is why plumber availability needs locking in early. A renovation that misses its rough-in slot can stall the entire trade sequence behind it.
The golden rule: keeping fixtures where they are is cheap
Replacing fixtures in their existing positions is the budget renovation: new toilet on the old flange, new taps on the old breeches, new basin over the old waste. The plumbing cost for a full like-for-like bathroom swap is often only a few thousand dollars.
Moving fixtures is where money goes. Relocating a toilet means rerouting a 100mm drain with correct fall, which on a concrete slab means cutting the slab. Moving a shower or basin means new hot and cold runs plus a relocated waste. Each moved fixture typically adds somewhere between several hundred and a few thousand dollars depending on floor construction, and slab homes sit at the expensive end.
Typical cost ranges
As a guide for metro Australia, and treating these as budgeting ranges rather than quotes:
- Full bathroom renovation plumbing (rough-in plus fit-off, fixtures unmoved): $3,000 to $6,000
- Each relocated fixture: add roughly $500 to $2,500, more if a slab must be cut
- Kitchen plumbing (sink, dishwasher, fridge water point): $800 to $2,500
- Adding a gas point or moving one: $300 to $900
- New tempering valve, isolation stops and compliance items: often several hundred dollars that quotes omit, so ask
Where budgets actually blow out
The predictable blowouts are discovered, not chosen: corroded galvanised pipe that cannot be reconnected to, old drainage with no fall, missing isolation valves, and non-compliant work from a previous renovation that must legally be rectified once opened up.
Build a contingency of 10 to 20 percent for plumbing in any renovation of a house older than 30 years. If the plumber opens a wall and finds 1970s galvanised pipe, replacing it while the wall is open is dramatically cheaper than reopening the same wall in two years.
Questions to settle before signing anything
Ask your plumber these at quote stage, in writing:
- Is the quote fixed price for the drawn layout, and what does a variation cost?
- Does it include the tempering valve, stops, and the compliance certificate?
- Who supplies the tapware and fixtures, and who is liable if supplied items are faulty?
- What happens if the slab or existing pipework throws up surprises?
- When do you need final fixture selections to keep the rough-in date?
Frequently asked questions
Can I supply my own taps and toilet to save money?+
Usually yes, and it can save real money, but the plumber's workmanship warranty then covers installation only, not the product. Buy from Australian retailers with WaterMark certified products; plumbers are prohibited from installing non-WaterMark fixtures.
Do I need council approval for bathroom plumbing?+
Like-for-like renovations generally do not need planning approval, but the plumbing work itself is still notifiable to the state regulator, and structural changes or new wet areas can trigger building approval. Your plumber and builder handle the notifications; your job is to keep the certificates they generate.
How long is a bathroom without water during renovation?+
Water to the rest of the house is usually only off for short windows during rough-in and fit-off, often under an hour each time. The bathroom itself is out of action for the full renovation, commonly 3 to 5 weeks for a standard room.