Buying a shower drain looks simple right up until the old one comes out and the new one does not line up. Drains are one of the few bathroom purchases where a few millimetres genuinely matter: the outlet has to match your pipe, the grate has to sit flush with your base or tile, and the whole assembly has to fit within the depth you actually have under the floor. This guide covers the dimensions that decide fit, whether you are renovating a condo in Vancouver, a century home in Halifax, or a basement bathroom on the Prairies.
Start with the pipe, not the grate
The most important number on any drain listing is the outlet size, meaning the diameter of the waste pipe the assembly connects to. Canadian plumbing codes, which build on the National Plumbing Code, generally call for a 2 inch drain line on showers, while bathtubs typically run on 1.5 inch lines. Enforcement happens provincially and municipally, so your local inspector has the final word, but the takeaway is the same from coast to coast: a shower drain and a tub drain are not interchangeable parts, and a tub-to-shower conversion usually involves the drain line itself, not just the visible hardware.
The grate or cover you see on the floor is a separate dimension entirely. Two drains with identical 2 inch outlets can have very different face sizes, so never buy on the look of the grate alone.
The five measurements that decide fit
Before you shop, note these numbers from your existing setup or your build plan:
- Outlet diameter. Usually 2 inches for a shower in Canada. Measure the inside diameter of the pipe if you can see it.
- Connection type. Solvent weld fittings glued to ABS or PVC, threaded connections, and compression style no-caulk fittings all occupy different amounts of vertical space and suit different pipe materials. ABS is common in Canadian homes, so check what you actually have before assuming.
- Drain location. Measure from the finished walls to the centre of the drain in both directions. Shower bases from makers like Maax and Kalia are built around fixed drain positions such as centre, offset, or corner, and moving a drain even a few centimetres means opening the floor.
- Opening size in the base. Acrylic and composite bases have a factory-cut drain hole sized for standard drain bodies, and the base's own spec sheet will state it.
- Available depth below. The drain body, the trap, and the pipe slope all live under the floor. A slab-on-grade basement bathroom offers very different clearance than a joisted second storey.
Point drains and linear drains size differently
A point drain is the familiar round or square grate near the centre of the floor. Faces commonly run from about 4 to 6 inches across, and fit is mostly a question of the outlet and the opening in your base or membrane.
A linear drain trades that single point for a long channel, usually placed against a wall or across a curbless entry. Lengths typically run from around 24 inches up to 60 inches, and length is the critical measurement. The channel does not always need to span the full wall, but the floor must slope toward it along its entire run, so the length you choose shapes the whole tile layout. For a wall-to-wall look, measure the finished opening rather than the rough framing.
Clearance rules, stated generally
Every drain needs a trap below it, and traps need room. As a general planning rule, allow for the drain body plus trap depth beneath the shower, keep the assembly accessible where your local code requires it, and avoid landing the drain directly over a joist. For tiled showers, the drain must also clamp or bond to the waterproofing membrane, which adds height to the assembly and is not optional. In colder parts of the country, drains in seasonal properties and unheated spaces deserve extra thought, since a trap that dries out or freezes over the winter stops doing its job. Treat all of this as planning guidance and confirm specifics with your inspector.
Common fit mistakes
- Buying the grate size instead of the pipe size. The face dimension tells you almost nothing about compatibility.
- Assuming the tub line will serve the new shower. That 1.5 inch line often needs upsizing to 2 inches in a conversion, which is floor-open work.
- Choosing a linear drain by look, not length. A channel that is too short for the slope plan leaves standing water at the dry end.
- Ignoring connection type. A solvent weld drain does not mate to a threaded fitting without adapters, and adapters eat vertical space.
- Forgetting the membrane detail on tiled showers. A drain for an acrylic base and a clamping drain for a tiled shower are different assemblies.
- Trusting the old drain's position. If you are changing bases, confirm the new base's drain location matches the existing rough-in before demolition day.
How to read a drain spec sheet
Manufacturers such as OS&B and Mountain Plumbing publish detailed spec sheets, and thirty seconds with one prevents most returns:
| Spec sheet term | What it tells you |
|---|---|
| Outlet size | The pipe diameter the drain connects to, the first thing to match |
| Connection type | Solvent weld, threaded, or no-caulk, which must suit your pipe material |
| Overall height or rough-in | How much vertical space the assembly needs below the finished floor |
| Flow rate | How much water the drain passes, worth checking against rain heads and body sprays |
| Material | ABS, PVC, brass, or stainless components, relevant for durability and compatibility |
| Listings | cUPC or CSA marks showing the product was evaluated to standards Canadian inspectors recognize |
Those listings matter here: reputable brands sold in Canada carry cUPC or CSA marks as a matter of course, while unlisted marketplace drains are where inspection-day surprises happen.
Matching the drain to the rest of the shower
Once fit is settled, finish is the easy part: most grates come in the same polished, brushed, and matte families as shower systems, so coordinating is straightforward. You can browse listed, Canada-wide shipped options in our drains collection, and if this renovation goes beyond the floor, our buying guides hub covers bases, doors, and valves in the same fit-first spirit.
Frequently asked questions
Are shower drains a standard size in Canada?
The pipe side is close to standard: codes generally require a 2 inch drain line for showers, and most assemblies are built around that outlet. The visible side is not standard at all: grate faces, channel lengths, and flange dimensions vary widely between models, so match the outlet first and then confirm the visible dimensions against your base or tile plan.
Can I reuse my tub drain for a new shower?
Usually not as-is. Tubs typically drain through 1.5 inch lines while showers generally require 2 inch lines under Canadian codes. A conversion normally includes reworking the drain line, so budget for that plumbing work rather than treating the drain as a swap-in part.
How do I choose the right linear drain length?
Work from your finished shower dimensions and your slope plan. The floor must fall toward the channel along its full length, so a drain that spans the wet area keeps the tile work simple. Measure the finished opening between walls, then check whether the spec sheet's stated length refers to the channel or the overall flange.
What is a clamping collar drain and do I need one?
A clamping collar drain sandwiches the shower's waterproofing membrane between the drain body and a bolted collar, sealing the wet floor to the drain. Tiled showers built over a membrane need one; acrylic and composite bases take a base-style drain instead. The two are not interchangeable, and this is the most common mix-up in tiled projects.
