Australian Bathroom Planning Guide

How to Measure Toilet Set-Out in Australia: S-Trap, P-Trap and the 140mm, 160mm, 180mm Question

If you are replacing a toilet in Australia, the first thing to check is not the seat shape or pan style. It is the set-out. For an S-trap toilet, set-out is measured from the finished wall to the centre of the floor waste. For a P-trap toilet, it is measured from the finished floor to the centre of the wall outlet.

Many Australian toilet replacements land around familiar numbers such as 140mm, 160mm and 180mm, but those are only useful as reference points. The safe move is to measure your own bathroom carefully before you order.

Trap type	Where the waste goes	How to measure set-out	What catches buyers out
S-trap	Into the floor	Measure horizontally from the finished wall to the centre of the floor outlet	Measuring from skirting, studs or the edge of the hole instead of the centre
P-trap	Into the wall	Measure vertically from the finished floor to the centre of the wall outlet	Looking for the same wall-to-floor number used on S-trap toilets

Why toilet set-out matters before anything else

Set-out decides whether the toilet will align properly with the waste point and sit neatly in the room. Get it right and the replacement process is straightforward. Get it wrong and you can end up with a pan sitting too far forward, visible gaps, extra labour or a toilet that simply does not suit the plumbing layout.

That is why set-out is one of the strongest practical search topics in the Australian market right now. It sits right at the point where a shopper moves from browsing products to trying to avoid an expensive ordering mistake.

Step 1: Work out whether you have an S-trap or a P-trap

Start by checking where the waste exits:

S-trap: the waste goes down through the floor.
P-trap: the waste runs into the wall behind the toilet.
Skew or offset situations: if the outlet is off to one side, stop and confirm the exact setup before buying.

If your existing toilet hides everything behind the pan, take photos and check the specification sheet for the current model if you still have it. Trap type changes the way set-out is measured, so it is worth slowing down here.

Step 2: Measure from finished surfaces, not unfinished ones

This is the mistake that causes a lot of replacement headaches. Toilets should be measured from finished surfaces, which means tiles, final wall linings and the completed floor level.

For an S-trap, measure from the finished wall behind the pan to the centre of the floor waste.
For a P-trap, measure from the finished floor up to the centre of the wall outlet.
Do not measure from skirting boards, bare studs, screed or the outer edge of the waste opening.

If the bathroom is mid-renovation, factor in the final tile build-up before locking in the toilet suite.

Step 3: Understand what 140mm, 160mm and 180mm actually mean

These numbers are common reference points in Australian toilet replacement conversations, especially for S-trap installations. They are not a shortcut that replaces measuring. They are simply the kinds of set-out figures you will often see in product specs, plumbing discussions and connector ranges.

A lot of toilets are designed to work across a range rather than one exact number, sometimes with a standard connector and sometimes with an extension bend or adapter. That gives installers some flexibility, but not unlimited flexibility.

A practical rule: treat common set-out numbers as a filter for which product specs to read next, not as a reason to skip measuring your own bathroom.

Can connectors or adaptors solve a mismatch?

Sometimes, yes. Some S-trap toilets can work with Vario bends, extension bends or other approved fittings that help cover a range of set-outs. But this is where many shoppers get overconfident. A connector can make a product more flexible, yet it does not turn every toilet into a universal fit.

A fitting may cover only a specific adjustment range.
Extra parts can affect how far the pan sits from the wall.
P-trap replacements still need the outlet height to match the product spec properly.

If your current toilet already sits unusually far forward or if the waste point looks offset, it is wise to confirm the installation plan before ordering.

The most common mistakes before buying a replacement toilet

Assuming all floor-outlet toilets share the same set-out.
Measuring the current pan position instead of the actual waste centre.
Using unfinished wall or floor lines during a renovation.
Treating an adaptor as a guaranteed fix without checking the specification sheet.
Choosing style first and fit second.

Bottom line

If you are shopping for a new toilet in Australia, measure the set-out first, confirm whether you have an S-trap or P-trap setup, and compare your result against the product specification before you fall in love with a particular design. It is the quickest way to narrow the field to toilets that are much more likely to fit cleanly.

Once your measurements are clear, choosing between back-to-wall, close-coupled or other non-smart toilet styles becomes much easier because you are comparing suitable options instead of guessing.