All advice / Planning and cost
Most of it, and here is why
In a full bathroom renovation, the plumber replaces most of the plumbing inside the room. The water supply lines, the drainage, the fixture connections and often the stop valves are all renewed. This is not because every pipe is failing — it is because the walls and floor are open, and this is the only practical time to do it.
Reusing 20-year-old pipes behind new tiles means the weakest part of the bathroom is the one you cannot see or reach. If a pipe fails after the tiles go on, fixing it means opening the wall. Replacing the plumbing during the renovation is cheaper than fixing it after.
Water supply lines
The pipes that carry hot and cold water to the basin, shower, bath and toilet are called supply lines. In older homes, these may be copper, galvanised steel or — in pre-1950s homes — lead.
Copper pipes corrode over time, especially at joints. Galvanised steel pipes rust from the inside out, narrowing the bore and reducing water pressure. Lead pipes are a health concern and should be replaced whenever they are found.
New supply lines are typically PEX (cross-linked polyethylene) or copper. PEX is flexible, resistant to corrosion and faster to install. Copper is traditional and durable. Both are compliant. The plumber roughs in the new lines to the positions set by the layout before the walls are sheeted.
Drainage
The waste pipes carry used water from the basin, shower and bath to the main drain. The toilet connects to a larger sewer pipe. In older homes, these may be clay, cast iron or PVC.
Clay drains crack and sag over time. Cast iron corrodes. Both can develop root intrusion at joints. PVC is the modern standard — it does not corrode, is smooth inside and lasts decades.
In a full renovation, the drain positions are set during the plumbing rough-in. If the layout is changing — for example, moving the shower from one end of the room to the other — new drain runs are laid in the slab or under the timber floor.
The toilet connection
The toilet connects to the sewer via a pan connector. In older homes, this may be a lead or rubber joint on a clay or cast iron stack. In a renovation, the connection is renewed with a PVC pan connector and a new cistern connection.
If the toilet position is changing, the waste pipe route changes too. In a house on a slab, this may mean cutting the slab to lay a new pipe run. In an apartment, the toilet is usually constrained by the stack position. Our apartment vs house guide covers the plumbing constraints in unit renovations.
Stop valves and isolation points
Stop valves let you shut off the water to a single fixture without turning off the whole house. Old gate valves seize over time and stop working. New ball valves or quarter-turn isolators are more reliable.
Replacing stop valves during the renovation is a small job — the plumber is already on site and the walls are open. It gives you the ability to isolate a leaking tap or toilet later without shutting off the main.
What about the hot water system?
A bathroom renovation does not automatically mean replacing the hot water system. If the existing unit is working well and has capacity for the new fixtures, it stays.
If the existing unit is old, undersized or unreliable, the renovation is a good time to upgrade. The plumber is already on site, and the new supply lines can be run to suit the new unit location.
Switching from an old electric tank to a heat pump or continuous-flow gas unit can reduce energy costs. This is a separate decision from the bathroom renovation itself, but the timing works well together.
How ETR manages plumbing
The plumbing scope is confirmed at the on-site measure. The written quote names what is being replaced, what is being reused and how the rough-in will be done. The plumber is licensed and all work is certified.
Every bathroom is waterproofed to AS 3740 after the plumbing rough-in, with a compliance certificate. The work is carried out under NSW Builder Licence 475204C with a 10-year workmanship warranty. A free on-site measure anywhere in Sydney is the starting point.
Frequently asked questions
Do all pipes need to be replaced during a bathroom renovation?
Not technically, but it is almost always recommended. The walls and floor are open during a renovation, and this is the only practical time to renew old plumbing. Reusing old pipes behind new tiles means the weakest part of the bathroom is the one you cannot reach.
What type of pipes are used in a modern bathroom renovation?
PEX (cross-linked polyethylene) or copper for water supply. PVC for drainage. PEX is flexible, corrosion-resistant and fast to install. Copper is traditional and durable. PVC is the standard for waste and sewer lines.
Can the toilet be moved during a bathroom renovation?
Yes, but it depends on the waste pipe route. In a house on a slab, the slab may need to be cut. In an apartment, the toilet is usually constrained by the stack position. The plumber assesses what is practical during the on-site measure.
How much does plumbing replacement add to a bathroom renovation cost?
Plumbing is part of the total renovation cost, not a separate charge. In a full renovation, the plumbing rough-in, fixture connections and certification are included in the scope. The cost varies with the number of fixtures and whether pipe positions are moving.
Should I replace the hot water system at the same time as the bathroom?
Only if the existing system is old, undersized or unreliable. If it works well and has capacity for the new fixtures, it can stay. The renovation is a convenient time to upgrade because the plumber is already on site.