One drain is usually sufficient up to around 1200 mm of opening width. Beyond that, or where the total shower output is high, two drains are normally used — either in opposition or as a single longer channel. The deciding factor is flow rate and achievable fall, not floor area alone.
When one drain is enough
- Opening up to approximately 1200 mm
- Single shower head or one rain head
- Floor can achieve an adequate fall to one side
When to use two drains
| Situation | Why |
|---|---|
| Opening wider than ~1200 mm | A single channel would need excessive fall across the floor |
| Rain head plus body jets | Combined output exceeds a single drain’s capacity |
| Shower open on two sides | Water reaches both halves of the floor |
| Very large wet room | Water must travel too far to a single drain |
| Accessible shower with level access | No threshold to contain water; capacity must exceed output |
Layout options for two drains
- Opposed wall drains — one at each end, floor falls to both sides from a central ridge
- Single long channel — a custom-length drain spanning the full wall eliminates the need for two
- Adjacent channels — two standard lengths butted together in one run
What actually decides it
Flow rate. Add up the output of every outlet in the shower and specify total drain capacity comfortably above it. Two drains are worth considering when the total is high, regardless of size.
Fall. Water has to reach the drain under gravity. The further the drain from the furthest point, the more fall is needed — and in level-access showers the fall is limited. Two drains halve the maximum travel distance.
Outlet capacity. Two drains normally need two outlets, or a shared outlet sized for the combined flow.
Tell us the shower dimensions and outlets and we will confirm the drainage layout. Request a Quote