Size a linear drain by the width of the shower opening and the water flow, not by the room size. As a working rule, the drain should span most of the shower opening width, and its flow rate should comfortably exceed the shower’s output.
Length: match the opening
| Shower opening width | Suggested drain length |
|---|---|
| Under 800 mm | Any length from 200 mm up to the opening width |
| 800–900 mm | 700–800 mm, or made to the full opening width |
| 900–1000 mm | 800–900 mm, or made to the full opening width |
| 1000–1200 mm | 900–1200 mm, or made to the full opening width |
| Over 1200 mm | Multiple drains, or a channel in several sections |
Drain length is made to order within 200 mm to 1200 mm — the figures above are a sizing guide rather than standard stock sizes.
A drain that spans most of the opening lets the whole floor fall in one direction with a manageable slope. If the drain is much shorter than the opening, water at the far corners has to travel further and the slope must increase.
Flow rate: match the shower
- Standard shower head — around 0.2–0.3 L/s
- Rain shower / large head — 0.4–0.6 L/s or more
- Multiple outlets in one shower — add the flows together
Specify a drain with capacity above the total, not equal to it. In level-access showers where water can spread across the floor, allow extra margin.
Also check
- Channel depth against available floor build-up
- Outlet position — horizontal, vertical or side — against the pipe route
- Grate type — steel or tile-insert — against the floor finish
Send us the opening width and shower specification and we will confirm the size. Request a Quote