Bathroom Renovation Plumbing: What Has to Be Decided Before the Tiler Arrives
Planning a bathroom renovation in Auckland? The plumbing happens in two stages. The rough-in, when pipes and wastes go into the walls and floor, comes before the linings, waterproofing and tiles. The fit-off, when the tapware, toilet and vanity go in, comes at the end. Almost every expensive bathroom change happens because something wasn't decided before rough-in. Once the tiles are on, moving a mixer even a short distance means cutting into finished work.
In short: lock in your fixtures, check your water pressure, decide the shower floor and waste, and plan the waterproofing hand-over before the walls are closed in. Tiled wet areas need a building consent, with plumbing and membrane inspections along the way.
1. Choose your fixtures first, not last
Your plumber sets pipe and waste positions to suit the exact products you're installing. The shower mixer, toilet pan and cistern, vanity and basin waste all come with instructions that set heights and positions. Ideally, have the actual products, or at least their spec sheets, before rough-in. We're happy to install fixtures you've bought yourself, we just need to see them early.
Shower: wall mixer or mixer with diverter, fixed head, rail or both, and the height of each.
Toilet: close-coupled, back-to-wall or in-wall cistern. Each needs a different waste and water set-out, and an in-wall cistern needs the framing planned around it.
Vanity: wall-hung or floor-standing, the waste position, and whether the tap is on the basin or on the wall.
Extras: a heated towel rail, bath filler or second basin all change what goes into the wall.
2. Check your water pressure
Lots of older homes still have a low-pressure hot water system, while most newer homes are mains pressure. The government's Smarter Homes guide to hot water cylinders and pipes explains the difference. Some tapware is designed only for mains pressure and won't perform well on a low-pressure system, so check before you buy. A renovation is also a good time to think about upgrading your hot water system.
3. Decide the shower floor and waste
A shower tray, a tiled shower with a centre waste, and a tiled level-entry shower with a strip drain each need different floor prep and waste positions. In a tiled shower, the floor has to fall to the waste. BRANZ's guidance on waterproofing tiled showers sets out the minimum fall, and notes that floor wastes need wide flanges designed to work with the membrane and tiles. Level-entry showers especially need planning with your builder, because the floor may need to be lowered.
4. Plan the waterproofing hand-over
The plumber, membrane applicator and tiler work one after another, and the joins between their work are where leaks start. BRANZ says penetrations, like the shower mixer coming through the wall, must be properly sealed before the membrane goes on. It also says membranes should be inspected before tiling and areas flood tested. Good communication between trades protects your bathroom and your warranties.
5. Check consent and inspections
Auckland Council's kitchen and bathroom renovation guidance says installing tiled wet areas, and adding new fixtures to existing spaces, need a building consent. On consented work, the council's list of inspection types includes a plumbing pre-line inspection before the linings go on, and a waterproofing membrane inspection for internal wet areas. These need booking at the right time, so build them into the programme.
6. Think about the future
Isolation valves: make sure you can get to them, so a tap or toilet can be serviced without turning off the whole house.
Backing in the walls: timber nogs for grab rails, towel rails and wall-hung fixtures.
Pipe insulation: insulate hot water pipes while the walls are open. Smarter Homes notes the Building Code requires hot water pipes to be insulated, and many older homes don't have it.
Photos: take photos of the open walls before they're lined. They're gold for anyone working on the bathroom later.
Frequently asked questions
Can I buy my own tapware and toilet?
Yes, we install customer-supplied fixtures all the time. Send us the product details before rough-in so we can check they suit your water pressure and set everything out correctly.
Do I need a site visit for a bathroom quote?
For bathrooms, we recommend one. Seeing the space, the existing pipes and the access underneath means we can give you an accurate, itemised quote rather than a guess.
Planning a bathroom renovation?
We handle full bathroom renovation plumbing, from rough-in to fit-off, including any drainage changes outside. See our plumbing and renovation services. Every repair and installation is backed by a 12-month workmanship guarantee. If something we've fitted fails because of our work, we'll fix it at no charge.
Call 021 025 83179, email info@poseidonplumbing.co.nz or send us a message to book a site visit and free quote. We work right across Auckland, including Central Auckland, the North Shore and Glen Eden.
Sources
General information only. Confirm consent requirements for your project with Auckland Council.
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