Plumbing a new build is not one job. It is five appearances on site, spread over months, each landing between other trades and each locking in decisions made before it.
Understanding the order is the difference between a smooth project and paying for the same work twice.
1. Underground and below slab
Sleeves, stub-ups and below-slab waste, set out from the drawings and fixed before the pour.
What locks in: the position of everything that comes up through the floor. A toilet stub-up in the wrong place after a pour is a concrete saw, a structural conversation and a bad week.
Least tolerance for error, highest cost of getting it wrong. This is where a careful contractor earns their money and a rushed one costs you.
2. Rough-in
Supply, waste and vent run within the structure. Stacks and risers. Everything that will be behind drywall.
What locks in: where every fixture can be. Rough-in is set out to finished dimensions — allowing for tile, backer board, cabinet depth and countertop overhang — not to framing dimensions. Getting that wrong is the classic remodel failure, and nothing reveals it until the finishes go on.
This is where fixture selection matters. Rough-in dimensions depend on the fixtures. A fixture chosen after rough-in means a compromise or a change order, and it is the most common avoidable cost on a project.
3. Top-out
Stacks and vents completed through the roof; the system made ready for test.
What locks in: venting. Venting is not optional and cannot be improvised later — a system that cannot breathe does not drain properly, and the fix after the fact is expensive.
4. Test and inspection
Pressure and air tests held, work presented for inspection where inspection applies.
What locks in: whether you can close the walls. A stage called before it is ready fails, gets re-presented, and costs schedule — and an inspector who has found one stage unready looks harder at the next.
A good sub checks before calling. That sounds obvious; it is not universal.
5. Trim-out
Fixtures, valves, trim and appliance connections set, connected and tested.
What locks in: the visible result. Trim-out comes after tile, after cabinetry is set, and after the countertop is templated and fitted. Setting fixtures before the finishes are in is how they get damaged and how they end up at the wrong height.
Then handover
Final test, notes on anything that moved from the drawings, isolation points identified, area left clean.
That last part matters more than it sounds. Knowing where the isolation valves are, and what was changed from the drawing, is what makes the property serviceable for the next thirty years.
Where projects lose money
- Fixtures chosen late, forcing compromise at rough-in
- Drawings that are not current, so the sub prices and sets out against a superseded sheet
- Compressed sequences, where rough-in gets squeezed because it is in the middle
- Nobody deciding when a drawing and a site condition disagree
- Stages called before they are ready, which costs more schedule than waiting would have
None of those are technical failures. They are coordination failures, and they are the ones that actually show up on the final account.
What actually delays a rough-in inspection
Almost never the plumbing. Rough-in fails on paperwork, on coordination and on decisions that were never made, and each of those is preventable weeks earlier.
Fixture selection not finalised. Rough-in heights and centers come from the fixture, not from a standard. A freestanding tub, a wall-hung pan or a shower valve with a different trim depth all move the pipework. Every week a selection stays open is a week the risk of rework stays open with it.
Blocking not in. A wall-hung basin or a grab rail needs timber or steel behind the board, and that is a carpentry item on a plumbing drawing. It gets missed, and it gets found after the board is on.
Penetrations not coordinated. Where the plumber, the electrician and the HVAC installer all want the same joist bay, the one who arrives last either notches something they should not or waits.
Test not held long enough. An inspector wants to see the system holding, not a gauge that was charged that morning. Charging the day before and leaving it is free; being asked to come back is not.
What we hand over, and why
A handover pack is not a courtesy. It is the difference between a warranty call that takes ten minutes and one that takes a day.
It contains the as-built deviations — where the installed run differs from the drawing, and why — plus photographs of every wall before it was closed, valve and isolation locations, test certificates with dates, and the model and serial of anything with a warranty attached.
The photographs are the part that gets used. Two years later, when somebody wants to hang a TV on a bathroom wall, a photograph of that wall open is worth more than any drawing.
If you are a contractor comparing bids, ask what the handover pack contains before you compare the numbers. A bid that does not include one is cheaper for a reason.