Moving the sink stack in a Canberra slab home.
Almost every Canberra home built between 1995 and 2015 has its kitchen waste set into the slab. Where it was poured is where the sink sits — unless you pay to move it. Here’s what a slab penetration actually costs in 2026, when a relocation is a 1.5 m no-problem job, and the drainage assessment we want on the table before we sign off on any layout change.
The waste pipe was set in 1998 — and the new kitchen has to live with it.
If your home is in Amaroo, Forde, Bonner, Harrison, Crace, Coombs, Wright or Denman Prospect, it is almost certainly a slab-on-ground build. The waste stack for the kitchen sink was cast into the slab before the concrete went down — usually a 40 mm or 50 mm PVC rise inside the wall cavity, with the run to the boundary trap set well below floor level. There is no subfloor. Nothing to crawl under. To move it, you cut the slab.
That single fact dictates a huge amount of what your renovation costs. A like-for-like kitchen replacement that keeps the sink in the same spot is straightforward joinery and benchtop work — we run our standard process and the drainage line item is near zero. A layout flip that pushes the sink to the other wall, or adds a working island, can add anywhere from $3,000 to $9,000 in drainage work alone. It is the single line item most likely to surprise an owner who has been quoted by a kitchen-only company that hasn’t thought about the slab.
The 1.5 m rule of thumb.
We call it the 1.5 m rule. Inside 1.5 m of the existing stack, and provided we can hold a fall of at least 1:60 to the boundary trap, we can usually extend the waste in PVC without cutting the slab — the new run sits inside the cabinetry and connects to the existing stub. We’ll re-vent if the existing branch becomes too long under AS/NZS 3500.2 and we’ll insulate the run where it crosses an external wall. Past 1.5 m, the geometry stops working: the fall runs out, or we’d need a back-vented loop that won’t pass a Certificate of Compliance. That’s when we chase the slab.
What a chase-out looks like.
A slab chase is not the disaster owners imagine. We saw-cut a straight channel about 200 mm wide along the line of the new drain, jackhammer out the concrete to a depth of around 100 mm, break through to the existing waste, lay new graded PVC, pressure test the line, then re-pour the channel in non-shrink grout and tie it back to the surrounding slab. A finishing screed brings it level for tiling or new floor coverings. Done well by a concretor who understands floor flatness, you will never see it once the new flooring is down. The licensed plumber lodges a Notice of Intention and issues a Certificate of Compliance on completion.
If your floor is warm, read this before you draw a new layout.
Cold-climate kitchens in Canberra are increasingly being renovated with in-slab hydronic heating retrofits, and a meaningful share of newer homes in O’Connor, Ainslie, Watson, Aranda and parts of Forrest already have it from the original build. The heating loops are 16 mm or 20 mm PEX-AL-PEX pipe set in serpentine patterns inside the slab pour. Cutting one is recoverable — it’s a repair coupling and a re-fill — but the cost and disruption to the rest of the floor is steep.
Before we sign off on a layout that crosses heating zones, we run a thermal-imaging scan during a heating run. The loops light up clear as day. We trace them onto the floor plan, mark the safe-cut corridors, and route the new drain only through those corridors. On three jobs this last winter in Inner North homes we redrew the island position by 200 mm to avoid a heating loop — it cost nothing to change on the page and saved a $15,000 floor rebuild. The thermal scan is the cheapest line item on the job.
Slab penetration — questions we get every week.
Why are sink waste pipes set into the slab in newer Canberra homes?
From the mid-1990s onward, most volume-built Canberra homes were built on engineered slab-on-ground with the kitchen waste stack set into the slab before the pour. There’s no subfloor to crawl under. Future relocation means chasing out the slab and re-laying drain. The original kitchen sat where the penetration was; renovating around it means working with that fixed point.
What does it cost to move a sink stack?
A short relocation under 1.5 m using a saw-cut chase, new PVC waste in fall, patched concrete and floor make-good usually lands in the $2,800–$4,500 range including the licensed plumber, concretor and floor reinstatement. A 3–5 m chase or a job that hits in-slab hydronic heating climbs to $5,500–$9,000. A full island relocation is usually $7,000 plus.
Do I need building approval to move a sink in the ACT?
Replacing a kitchen in the same footprint and re-using the existing connections does not usually need an Access Canberra building approval. The moment you alter sanitary drainage, the plumbing work itself must be done by an ACT-licensed plumber under the Plumbing and Drainage Act 2008, with a Notice of Intention and a Certificate of Compliance lodged. Removing a structural wall to open the kitchen triggers a separate building approval through a private certifier.
What do you want to see before signing the layout?
A sewer service location plan from Iconwater (or the as-built hydraulic plan if the home is under 15 years old), a tape measurement from the existing waste to the proposed new sink, and a thermal scan if the home has in-slab hydronic heating. With those three we quote the drainage line item accurately rather than estimate.
Want the slab line item priced before you fall in love with the layout?
Send us a photo of the existing sink position and a rough sketch of where you want it to go. We’ll come back with a clear yes-or-no on the 1.5 m rule and an honest range for the drainage work before you sign anything.