Slow drainage is usually caused by debris in the trap or channel, restricted flow through the grate, or an installation issue — insufficient fall, an undersized outlet, or too many bends in the waste pipe. Check the simple causes first.
Diagnose in this order
| Check | Symptom | Action |
|---|---|---|
| Grate surface | Hair and soap visible on top | Lift the grate and clear it |
| Hair trap | Water slows gradually over weeks | Remove and clean the trap |
| Channel floor | Water sits in the channel | Clear the full length, especially the far end |
| Odour trap | Slow from day one, or after a long period unused | Clean the trap; check it is not blocked by hardened debris |
| Tile-insert grate | Always slow, worsens with debris | Clean around the insert edges; check flow rate suits the shower |
| Waste pipe | Slow regardless of cleaning | Mechanical clean of the pipe run |
| Installation | Slow from the day it was installed | Check fall, outlet size and bends |
If it has always been slow
The cause is almost certainly installation rather than debris:
- Insufficient fall on the waste pipe, or the floor slope reduced to fit the drain
- Outlet too small for the flow through the drain
- Too many bends in the waste run, each adding resistance
- Drain capacity below the shower output — particularly with rain showers
- Long horizontal run without adequate fall
If it has become slow over time
The cause is almost certainly build-up. Hair passing the grate settles in the channel and trap. Clean the grate weekly in households with long hair — this prevents the problem rather than treating it.
What not to do
- Do not use chemical drain cleaners as routine maintenance — they damage seals and finishes and leave the underlying debris in place.
- Do not remove the hair trap as a “solution” — it protects the pipe.
Related: preventing hair clogs · cleaning a linear drain