Bathroom Renovation Plumbing Checklist: What to Get Right Before Waterproofing and Tiling

Bathroom renovations can look simple once the tiles, vanity and tapware are chosen, but the plumbing behind the walls and under the floor is what decides whether the bathroom works properly long term.

Before waterproofing and tiling, the plumbing layout needs to be checked carefully. Toilet set-outs, shower wastes, floor wastes, vanity plumbing, mixer positions, drainage falls, pipe condition and hot water supply all need to be planned before the bathroom is sealed up.

This matters across Brisbane, the Gold Coast and South East Queensland because homes vary so much. A bathroom renovation in an older Queenslander, post-war home, slab house, townhouse, duplex, unit or acreage property can all involve different plumbing access, drainage and compliance requirements.

JR Gas & Water provides bathroom renovation plumbing in Brisbane and the Gold Coast, along with broader plumbing services across Greater Brisbane and the Gold Coast. For homeowners, builders, tilers and renovation teams, getting the plumber involved early can help avoid expensive rework once waterproofing and tiles are already finished.

Quick answer

Before waterproofing and tiling a bathroom, homeowners should confirm the plumbing layout, toilet set-out, shower waste, floor waste, vanity plumbing, mixer positions, drainage falls, water pressure, hot water supply, pipe condition and access points with a licensed plumber. Once tiles are installed, plumbing mistakes become much harder to fix without cutting walls, floors or finished surfaces.

Why plumbing should be planned before tiles and waterproofing

A bathroom renovation should not start with tile colours. It should start with the plumbing layout.

The plumbing decides:

• Where the toilet can realistically go

• Whether the shower waste can drain correctly

• Whether the floor has enough fall

• Whether the vanity can be centred

• Whether wall mixers will fit inside the wall

• Whether the bath can be connected properly

• Whether old pipework should be replaced while walls are open

• Whether the hot water system can support the new bathroom layout

• Whether future servicing will be possible

• Whether the renovation needs drainage changes or compliance work

Once waterproofing is complete and tiles are laid, changes become harder. A small mistake with a toilet set-out, mixer depth, waste location or pipe route can mean cutting into new finishes.

That is why JR Gas & Water’s bathroom renovation plumbing service is built around planning the plumbing scope before demolition, rough-in, waterproofing, tiling and final fit-off.

Bathroom renovation plumbing checklist before waterproofing

Before waterproofing starts, work through these key plumbing items.

1. Toilet location and set-out

Toilets are one of the most important fixtures to check early because they are not always simple to move.

Your plumber should confirm:

• Existing toilet set-out

• New toilet pan requirements

• Whether the waste exits through the floor or wall

• Whether the toilet can move without major drainage work

• Whether the new pan suits the existing pipe location

• Whether the cistern and pan have enough clearance

• Whether the floor structure or slab limits relocation

• Whether body corporate approval may apply in units or townhouses

A simple like-for-like toilet replacement is very different from moving the toilet to a new position. If the toilet is leaking, running, blocking or unreliable before renovation starts, it may also be worth checking whether toilet repairs or a full replacement better suits the plan.

2. Shower waste and drainage fall

The shower may look like a simple fixture choice, but drainage fall is critical.

Check:

• Shower waste position

• Waste pipe size and condition

• Fall to the waste

• Whether the shower is hobless, walk-in or enclosed

• Whether a linear grate is being used

• Whether large-format tiles will affect fall

• Whether the waste can connect properly to existing drainage

• Whether there is enough floor depth for the proposed setup

Walk-in showers and linear drains can look clean, but they need careful set-out. If the fall is wrong, water can sit in the shower, creep toward the bathroom floor or create ongoing nuisance drainage issues.

If the renovation involves broader waste or sewer changes, JR Gas & Water’s drainage plumbers can help assess what is practical before the bathroom is tiled.

3. Floor waste position

Floor wastes are easy to overlook until the tiler is on site.

Confirm:

• Whether a floor waste is required

• Where water will naturally fall

• Whether the grate location suits the room

• Whether the pipe can connect correctly

• Whether tile set-out will work around the grate

• Whether the floor waste clashes with the vanity, toilet or shower screen

A floor waste should be planned before waterproofing, not squeezed in later. If it is positioned poorly, the bathroom may not drain the way it should.

4. Vanity plumbing

Vanities often cause problems when the cabinet design does not match the plumbing.

Check:

• Hot and cold water point locations

• Waste outlet position

• Drawer clearance

• Basin waste location

• Mixer location

• Wall-hung vanity fixing points

• Whether the pipework needs to be centred

• Whether the trap will fit neatly inside the cabinet

Wall-hung vanities, twin vanities and drawer-style cabinets need careful planning. A vanity can look perfect on paper but clash with the existing water or waste points once it arrives.

5. Tapware, mixers and shower outlets

Tapware should be chosen before rough-in, not after the walls are closed.

Check:

• Mixer height

• Mixer depth

• Finished wall thickness

• Shower outlet position

• Rail shower or overhead shower location

• Bath spout position

• Basin mixer compatibility

• Access for future servicing

• Whether the tapware suits the wall cavity depth

If you are only updating fixtures without changing the bathroom layout, JR Gas & Water can help with tapware replacement, tapware repairs and shower head replacement. For a full renovation, those same fixture choices need to be coordinated with the rough-in stage.

6. Bath plumbing

Baths need more planning than many homeowners expect, especially freestanding and back-to-wall styles.

Check:

• Bath waste position

• Trap access

• Mixer or spout location

• Water point locations

• Overflow requirements

• Floor structure

• Clearance around the bath

• Whether future access will be possible

Freestanding baths can be difficult if the waste is not in the right position. Back-to-wall baths can also create access issues if pipework, wastes or valves are hidden without proper planning.

7. Hot water supply

A bathroom renovation can increase hot water demand.

This is especially true if you are adding:

• A larger shower head

• Twin showers

• A freestanding bath

• A second bathroom or ensuite

• Higher-flow fixtures

• A family bathroom upgrade

• More simultaneous hot water use

If the current system already runs out, recovers slowly or struggles in cooler weather, the renovation is a good time to review it.

JR Gas & Water can help compare suitable hot water systems, including electric hot water systems, heat pump hot water systems, gas storage hot water systems and instant gas hot water systems. If the system is faulty before the renovation starts, hot water repairs and servicing may also be needed.

Common bathroom renovation plumbing mistakes

Many bathroom renovation problems come from decisions made too late.

Common mistakes include:

• Choosing fixtures before checking pipe locations

• Moving toilets without confirming waste options

• Buying a vanity that clashes with existing plumbing

• Setting wall mixers at the wrong depth

• Not checking shower fall before tiling

• Forgetting the floor waste location

• Leaving old pipework behind new tiles

• Not pressure testing before sheeting

• Not coordinating with the waterproofer

• Not checking hot water capacity

• Assuming all toilets have the same set-out

• Assuming all mixers suit all wall depths

• Not allowing access for future servicing

• Treating drainage as an afterthought

A bathroom renovation is the best time to fix plumbing properly. Once the room is finished, every hidden mistake becomes more expensive.

Disconnection, rough-in and fit-off: the plumbing stages explained

A good bathroom renovation usually involves more than one plumbing visit.

Disconnection and isolation

Before demolition, existing water and waste services may need to be safely isolated or disconnected. This helps the builder or demolition team start without damaging active pipework or creating leaks.

Rough-in plumbing

This is where the new plumbing layout is set up before walls and floors are closed.

Rough-in work can include:

• Moving water points

• Altering waste pipework

• Setting shower mixers

• Setting bath and vanity pipework

• Positioning floor wastes

• Altering toilet plumbing

• Preparing for bidets or specialty fixtures

• Checking drainage and pipe routes

JR Gas & Water’s bathroom renovation plumbing page is the best service page for this type of staged renovation work.

Testing before close-up

Before waterproofing and tiling, pipework should be checked and tested where required. This helps reduce the risk of hidden leaks behind new walls or under new floors.

Final fit-off

Once waterproofing, tiling and cabinetry are complete, the plumber returns to fit off toilets, vanities, showers, baths, tapware and accessories.

This is where correct earlier planning pays off. If the rough-in was accurate, fit-off is much smoother.

Check old pipework before closing the walls

A bathroom renovation is one of the best chances to replace old or questionable pipework because the walls and floors are already open.

Older Brisbane and Gold Coast homes may have:

• Ageing copper pipework

• Old galvanised pipework

• Previous renovation changes

• Corroded fittings

• Unsupported pipes

• Old isolation valves

• Poorly routed hot and cold lines

• Signs of previous leaks

• Pipework affected by water hammer

• Drainage that no longer suits the new layout

If you cover old pipework behind new tiles, a future leak may require cutting into the new bathroom.

If there are damp areas, water stains, unexplained moisture or previous leak concerns, JR Gas & Water can help with leak detection and water leak repairs before the renovation continues.

Pressure testing before waterproofing

Pressure testing is a key step before the bathroom is closed up.

It is especially important when:

• Pipework has been moved

• Existing pipework has been joined to new pipework

• New wall mixers are installed

• A vanity has moved

• The shower has changed position

• A bath has been added

• The bathroom is upstairs

• There are rooms below the bathroom

• The property has had past leaks

A leak behind finished tiles can be disruptive and costly. Testing before waterproofing and tiling is a practical way to reduce that risk.

Waterproofing and plumbing need to be coordinated

Bathroom waterproofing and plumbing need to work together.

The plumber, waterproofer, tiler, builder and cabinetmaker should be aligned on:

• Shower waste position

• Floor waste position

• Mixer penetrations

• Pipe penetrations

• Bath waste access

• Vanity waste location

• Finished wall thickness

• Tile set-out

• Falls to drains

• Access panels where needed

• Timing between rough-in and waterproofing

• Final fit-off timing

Changing pipework after waterproofing can damage the waterproofing system and create delays. That is why the plumbing should be confirmed before the bathroom moves to the next stage.

Moving plumbing in a bathroom renovation

Moving plumbing can be practical, but it depends on the home.

Common layout changes include:

• Moving a vanity

• Moving a toilet

• Changing a bath to a shower

• Adding a second shower outlet

• Installing a wall-hung vanity

• Installing wall mixers

• Adding a floor waste

• Creating an ensuite

• Turning a laundry into a bathroom

• Adding a bidet or bidet seat connection

The difficulty depends on:

• Slab or timber floor construction

• Underfloor access

• Existing pipe routes

• Drainage fall

• Wall depth

• Fixture selections

• Body corporate rules

• Shared services

• Existing drainage condition

In a timber floor home, underfloor access may make some changes easier. In a slab home, waste relocations may require concrete cutting and reinstatement. In units and townhouses, approvals and shared services may affect what can be done.

Bathroom renovations in older Brisbane homes

Older Brisbane homes can hide plumbing surprises.

Common issues include:

• Ageing pipework

• Old drainage layouts

• Timber floor movement

• Limited wall depth for mixers

• Previous DIY plumbing

• Low or inconsistent pressure

• Old hot water systems

• Water-damaged framing

• Out-of-level floors

• Poor past renovations

• Tight access around existing services

High-set homes can offer useful access underneath, but that does not mean every change is simple. Waste fall, pipe routes, fixture positions and compliance still need to be checked.

Bathroom renovations on the Gold Coast

Gold Coast bathrooms can bring different challenges.

Common issues include:

• Coastal corrosion

• Duplex access limits

• Townhouse and body corporate requirements

• Slab construction

• Flat sites with drainage constraints

• Shared plumbing services

• Tight wet area layouts

• Limited access for pipe alterations

• Moisture and ventilation concerns

If the renovation is in an apartment, unit, duplex or townhouse, check access, approvals and service locations before locking in the layout.

Slab homes, townhouses and body corporate bathrooms

Bathrooms in slab homes and body corporate properties often need extra planning.

Ask these questions early:

• Can the toilet waste be moved?

• Can the shower waste be repositioned?

• Will concrete cutting be required?

• Are there rooms or units below?

• Are services shared?

• Does body corporate approval apply?

• Are acoustic requirements relevant?

• Can future servicing access be maintained?

• Will the renovation affect neighbouring properties?

A plumber should assess these details before fixtures are ordered and before demolition starts.

Toilets, tapware and showers: when a smaller update is enough

Not every bathroom needs a full renovation.

In some homes, a smaller plumbing upgrade may solve the main issue without replacing the whole bathroom.

For example:

• A cracked, stained or outdated toilet may suit a toilet replacement

• A leaking or running toilet may suit toilet repairs

• Worn mixers or old tapware may suit tapware replacement

• Dripping taps may suit tapware repairs

• Poor shower performance may suit a shower head replacement

This is useful if the bathroom still looks acceptable but the fixtures are unreliable. A full bathroom renovation plumber is more relevant when walls, floors, waterproofing, drainage or fixture positions are changing.

Drainage and sewer checks before renovating

If the bathroom has drainage symptoms before renovation, do not tile over the problem.

Warning signs include:

• Slow shower drainage

• Gurgling floor wastes

• Bad smells

• Toilets slow to flush

• Water backing up

• Repeated toilet blockages

• Wet patches near bathroom walls

• Outdoor overflow issues

• Tree roots suspected in drains

For recurring drain problems, a CCTV drain inspection can help identify pipe condition before renovation work begins. If there are damaged sewer lines, root intrusion or broken sections, sewer repairs may need to be considered before finishing the bathroom.

For broader drainage problems, JR Gas & Water’s drainage plumbers can help assess the best path forward.

Hot water performance after a bathroom renovation

A new bathroom can expose an old hot water problem.

Review your hot water system if:

• The old system already runs out

• The new shower has higher flow

• A bath is being added

• More bathrooms will be used at once

• A twin shower is planned

• The household has grown

• Recovery time is slow

• The system is old or unreliable

• The renovation includes a new ensuite

The right hot water system depends on the household, not just the bathroom. Available space, power supply, gas availability, usage patterns and installation requirements all matter.

JR Gas & Water can help compare hot water systems or arrange hot water repairs and servicing if the current system is not performing properly.

Bathroom renovation plumbing cost factors

Bathroom renovation plumbing costs depend on access, scope and how much is changing.

Common cost factors include:

• Whether fixtures stay in the same position

• Whether the toilet is moving

• Whether shower or bath wastes need altering

• Whether concrete cutting is required

• Whether old pipework needs replacing

• Whether drainage work is needed

• Whether a floor waste is being added

• Whether the bathroom is upstairs

• Whether there are rooms below

• Whether the property is on a slab

• Whether body corporate requirements apply

• Whether specialty fixtures are being installed

• Whether hot water tempering is required

• Whether extra visits are needed around other trades

JR Gas & Water’s bathroom renovation plumbing service is the most relevant starting point for renovation-specific quoting. For smaller plumbing tasks, the broader service work pricing page can help homeowners understand how service work is structured.

What homeowners can safely plan themselves

You can prepare useful information before booking a plumber.

Helpful details include:

• Photos of the existing bathroom

• A rough layout sketch

• Fixture selections

• Vanity details

• Toilet model or set-out details

• Shower type

• Bath type

• Tapware choices

• Whether fixtures are staying or moving

• Builder, tiler or waterproofing notes

• Timing preferences

• Access notes

• Any known leaks, smells or drainage issues

Do not move pipework, alter wastes, modify valves, connect fixtures or perform plumbing work yourself. Bathroom plumbing should be handled by a licensed plumber.

What needs a licensed plumber

A licensed plumber should handle:

• Bathroom disconnection and isolation

• Rough-in plumbing

• Toilet relocation

• Toilet installation

• Shower waste installation

• Vanity water and waste connections

• Bath water and waste connections

• Mixer installation

• Pipework replacement

• Drainage changes

• Floor waste planning

• Pressure testing

• Tempering valve work where required

• Hot water connections

• Leak repairs

• Final fixture fit-off

• Compliance-related plumbing work

Gas work should always be completed by a licensed gas fitter. Electrical work should always be completed by a licensed electrician.

Signs your bathroom plumbing needs attention before renovating

Before spending money on new tiles and fixtures, look for plumbing warning signs.

These include:

• Slow shower drainage

• Gurgling floor wastes

• Bad smells

• Water stains on walls or ceilings

• Low water pressure

• Hot water running out quickly

• Noisy pipes

• Water hammer

• Old isolation valves

• Rusty fittings

• Previous leak repairs

• Damp vanity cabinets

• Mould around wet areas

• Cracked tiles near wet zones

• Soft flooring

• Wet patches outside near bathroom walls

If any of these are present, it is worth getting the plumbing checked before the renovation is sealed up.

Bathroom renovation plumbing checklist

Before waterproofing and tiling, confirm:

• Toilet set-out is correct

• Shower waste is correctly positioned

• Floor waste is planned

• Vanity waste and water points suit the cabinet

• Wall mixers are at the correct depth

• Tapware suits the finished wall thickness

• Bath waste and access are planned

• Old pipework has been checked

• Hot and cold lines are secure

• Drainage fall has been confirmed

• Pipework has been pressure tested

• Hot water supply suits the new bathroom

• Any leaks have been repaired

• Waterproofing penetrations are coordinated

• Access for future servicing has been considered

• Compliance requirements have been allowed for

• Licensed trades are handling plumbing, gas and electrical work

This checklist is much easier to work through before tiles are installed than after the renovation is finished.

FAQs

Do I need a licensed plumber for a bathroom renovation?

Yes. Bathroom renovation plumbing should be completed by a licensed plumber. This can include disconnection, rough-in, water pipe alterations, drainage changes, fixture installation, hot water tempering, testing and final fit-off.

When should I get a plumber involved in a bathroom renovation?

Before demolition is best. Early plumbing advice can help confirm whether the proposed layout is practical before waterproofing, tiling, cabinetry and fixtures are locked in.

Can JR Gas & Water help with bathroom renovation plumbing?

Yes. JR Gas & Water provides bathroom renovation plumbing across Brisbane, the Gold Coast and South East Queensland, including disconnection, rough-in, drainage changes, fixture fit-off, testing and compliance-focused plumbing support.

Can I move my toilet during a bathroom renovation?

Often yes, but it depends on the existing waste location, floor construction, slab access, pipe fall and the new toilet type. Moving a toilet in a slab home can be more complex than moving one where there is underfloor access.

Should I replace old bathroom pipework during a renovation?

If the walls or floors are already open and the pipework is old, corroded, damaged or poorly installed, replacement may be worth considering. It is usually easier to replace questionable pipework during renovation than after new tiles are installed.

Why is my new shower draining slowly?

Slow drainage may be caused by poor fall, a waste issue, pipework restrictions, a blockage or incorrect set-out. If a shower drains slowly after renovation, it should be checked before it becomes a bigger issue.

Can a bathroom renovation affect hot water performance?

Yes. Larger showers, baths, twin showers or extra bathrooms can increase hot water demand. If the existing hot water system is already struggling, the renovation may make the issue more noticeable.

Do bathroom renovations need Form 4 plumbing compliance?

Some bathroom renovation plumbing work may require Form 4 lodgement, especially where regulated plumbing work, fixture relocation, new pipework or drainage alterations are involved. Your plumber should advise what applies to the work being completed.

Planning a bathroom renovation?

Before waterproofing and tiles go in, make sure the plumbing is right.

JR Gas & Water can help with bathroom renovation plumbing, rough-ins, fixture fit-off, drainage checks, leak repairs, toilet upgrades, tapware replacement, hot water advice and licensed plumbing support across Brisbane, the Gold Coast and nearby South East Queensland areas.

Start with the bathroom renovations plumber page, view broader plumbing services in Greater Brisbane and the Gold Coast, check service work pricing, or send plans and photos through the quote request and bookings page.