S-trap vs P-trap vs Skew trap toilets in Australia: what it means and how to choose
S-trap vs P-trap vs skew trap toilets: what it means and how to choose the right one in Australia
If you’re toilet shopping and you keep seeing S-trap, P-trap, skew trap (or “universal”), this is the bit that decides whether your new suite will actually connect up properly. Style is fun. Plumbing fit is non-negotiable.
When you’re ready to browse, here’s the full range of toilets. toilets.
The 10-second difference
S-trap (floor outlet)
Waste outlet goes down into the floor.
Look for: the pipe disappearing into the tiles.
P-trap (wall outlet)
Waste outlet goes back into the wall.
Look for: the pipe going straight into the wall behind the pan.
Skew trap (offset outlet)
Waste outlet is offset to one side.
Look for: the outlet point is noticeably off-centre.
Note: if you need a skew trap, you’ll usually need to know if the outlet points left-hand (LH) or right-hand (RH) as you face the toilet.
The cheat sheet for identifying your trap
- Look behind the toilet: if the pipe goes into the floor → S-trap
- Look behind the toilet: if the pipe goes into the wall → P-trap
- Look at the side/position of the outlet: if it’s offset left or right → Skew trap (LH or RH)
Still unsure? Don’t guess. The safest move is to measure set-out properly before you order.
What is a “universal trap” toilet (Uni-trap)?
A lot of modern toilet suites are now universal trap, which means the same suite can usually be configured for either S-trap or P-trap.
How they do it: universal setups commonly use a plastic connector (often called a connector or Vario bend) to convert the outlet and reach the floor for S-trap installs. It’s basically the secret weapon of modern toilet flexibility.
Universal does not mean “fits absolutely everything”, though. You still need to confirm set-out and outlet height so the suite sits where it should.
The set-out detail people mix up (horizontal vs vertical)
This is the most common mistake: people look for the wrong measurement direction.
- S-trap set-out is horizontal: measure from the finished wall (tiles) to the centre of the floor outlet.
- P-trap set-out is vertical: measure from the finished floor (tiles) to the centre of the wall outlet.
Extra important for P-traps: the height of the outlet from the floor matters, and it can vary between brands and suites. So for P-traps, you’re thinking about:
- outlet height from the floor
- and how the connection lines up at the wall
Measure from finished surfaces, not studs or raw sheeting. In a reno, that small difference can be enough to ruin the fit.
(We’ll publish the step-by-step next: How to measure toilet set-out in Australia.)
When you might need a skew trap (and why LH/RH matters)
Skew trap tends to come up when:
- you’re replacing an older toilet and the outlet wasn’t centred
- the waste was routed around a joist or other constraint
- the toilet isn’t positioned squarely in the room
If you suspect skew, confirm whether it’s left-hand or right-hand as you face the toilet, because ordering the wrong side can be a fast way to waste a week.
Quick table: trap types at a glance
| Trap type | Outlet location | Measurement direction | Best for |
|---|---|---|---|
| S-trap | Floor | Wall to centre of pipe (horizontal) | Standard Aussie homes |
| P-trap | Wall | Floor to centre of pipe (vertical) plus outlet height check | Apartments, modern builds |
| Skew trap | Offset (LH or RH) | Confirm left/right offset from centreline | Older or awkward plumbing layouts |
Which one should you choose?
You don’t choose trap type for fun. You match what your bathroom has, unless you’re doing plumbing changes.
If you’re replacing an existing toilet
Match the current setup:
- S-trap to S-trap
- P-trap to P-trap
- Skew trap if your outlet is offset (confirm LH or RH)
If you’re renovating
You’ve got more options, but plan it early:
- Decide whether waste runs in the floor or wall
- Confirm finished wall and floor thickness
- Confirm P-trap outlet height if you’re going into the wall
- Then choose a suite that matches the planned set-out
Browse options once you’ve confirmed your type with toilets.
FAQs
What’s the difference between an S-trap and a P-trap toilet?
S-trap connects into the floor. P-trap connects into the wall. The key difference is the outlet direction and the measurement direction for set-out.
Can I change an S-trap toilet to a P-trap toilet?
It’s possible during a renovation, but it usually means changing plumbing. For a simple replacement, it’s best to match what you already have.
What is a skew trap toilet?
A skew trap toilet is designed for an outlet that isn’t centred. You’ll usually need to confirm whether it’s left-hand or right-hand as you face the toilet.
Are universal trap toilets worth it?
They can be, especially if you want more suite options or flexibility during a renovation. They often use a connector (like a Vario bend) to suit different installations, but you still need to confirm set-out.
Do I need a plumber to figure this out?
If you’re confident identifying the outlet location and taking measurements from finished surfaces, you can usually work it out. If you’re uncertain, a quick check can save you ordering the wrong suite.