Bathroom Renovation Plumbing Checklist

A bathroom renovation is where the most plumbing decisions get made at once, and mistakes here are expensive because they are buried behind tiles and waterproofing. Getting the plumbing sequence and the fixture choices right before the walls close up saves you tearing them open later. This checklist walks through the plumbing side of a bathroom reno in the order the work happens, from rough in to fit off, so nothing gets forgotten while the walls are open.

Plan the layout and set out first

Before a single pipe moves, lock in where everything goes. Moving a toilet or shower waste across the room means moving drainage under the floor, which is the costliest change, so decide early. Check the toilet set out, the distance from the wall to the waste, because it determines whether you need an S trap or a P trap pan and whether an existing pan will fit. Confirm the fall available for the shower and floor wastes, because drainage relies on gravity and a floor that is too flat will pond. Mark the mixer and outlet heights against the vanity, bath and shower rail before the plumber roughs in.

The rough-in stage

Rough in is the concealed pipework done before lining and tiling. Your plumber runs and pressure tests the hot and cold water lines and the drainage, and sets the outlets to the marked positions. This is the moment to fit isolation valves so each fixture can be shut off individually later without turning off the house, and to confirm the pipe material, covered in PEX vs copper pipe. Any hot water and tempering arrangement is set now too, per tempering valves and TMV compliance. Get the rough in inspected and photographed before it is covered: those photos are gold if anything ever needs locating.

Waterproofing before tiling

Waterproofing is a mandatory, standards governed step done after rough in and before tiling, to the wet area standard AS 3740. It is not a plumbing task as such but it is intimately tied to the drainage falls and the floor waste, and it must be done by a competent person and certified. A floor waste that is not correctly integrated with the membrane is a leak waiting to happen. Do not let tiling start until the waterproofing is done and has cured.

Choosing the fixtures

With the rough in set you fit off the visible fixtures. Key choices:

• Tapware and mixers, matched to the outlet type and, ideally, a good WELS water efficiency rating to cut water use.
• Toilet suite, matched to the set out (S or P trap) and with a WELS rating.
• Shower, with a water efficient rose and a floor or wall waste sized for the flow.
• Basin and vanity, with the waste and trap that suit the cabinet.
• Bath, with access to its waste and overflow if it is against a wall.
• Floor waste in the correct low point, and an exhaust fan for ventilation.

WELS ratings are worth attention: a higher star tapware and toilet noticeably reduces water and, on the hot side, energy use over the life of the room.

Sign-off and records

The plumbing work must be certified with a compliance certificate, and you should keep it with the waterproofing certificate for the property records and any future sale. Choosing the plumber who does all this is covered in how to choose a licensed plumber. If the reno includes a new or relocated hot water unit, size it with the continuous flow vs storage sizing guide and the hot water system types guide. A dripping mixer discovered during the reno is a quick fix, see replacing a tap cartridge.

When you are buying tapware, a toilet suite, wastes and a vanity, matching model numbers and certification matters, which is where buying plumbing parts safely helps. Browse current listings for fixtures and trades, and suppliers or plumbers can list a business to reach renovators. Sort the plumbing before the tiler arrives and the rest of the bathroom goes together the easy way.

Common questions

When in the renovation is waterproofing done?

After the plumbing rough in and before the tiling. The waterproof membrane has to tie in with the floor wastes and the drainage falls, so it cannot go down until the pipework is set, and tiling cannot start until the membrane is done and cured. Rushing this sequence is how leaks end up behind finished tiles.

Do I need approval for a bathroom renovation?

Often, particularly if you are relocating fixtures, changing drainage, or doing structural work, and the plumbing itself always needs a compliance certificate. A cosmetic refresh that reuses the existing outlets is simpler than a full reconfiguration. Ask your plumber and, where needed, your local council what applies before you start knocking out walls.

What is the difference between rough in and fit off?

Rough in is the concealed pipework run and tested before the walls and floor are lined and tiled, setting the outlets in the right positions. Fit off is the later stage where the visible fixtures, the tapware, toilet, basin and shower fittings, are installed onto that rough in once the room is tiled. Getting the rough in positions right is what makes the fit off go smoothly.

How long does the plumbing take in a bathroom reno?

The plumber typically attends at least twice, once for the rough in early and once for the fit off near the end, with the tiling, waterproofing and cabinetry happening in between. The plumbing days themselves are a small part of the calendar, but their timing controls the whole job, so a delay to the rough in holds up everyone who follows.