Plumbing and maintenance
Waste traps: bottle, P, S and what they do
Common mistakes to avoid
Shallow traps buy depth under a bath or shower, but a reduced seal is more prone to evaporation and siphonage.
The short answer
A trap holds a water seal that stops drain air entering the room. The type chosen affects depth, flow and how easily it can be cleaned.
What to check
Point 1
Bottle traps look neat under exposed basins but restrict flow more than a tubular trap and clog sooner.
Point 2
Shallow traps buy depth under a bath or shower, but a reduced seal is more prone to evaporation and siphonage.
Your questions answered
Why does my trap keep blocking?
Often the type or the fall. A bottle trap under a hair-heavy basin will always block more.
Can traps be omitted?
No, every fitting connected to drainage needs a trap seal.
Connected pages on this site
Talk through waste traps with the person doing the work
Send a short description of the room and what you want to change. We'll come back with practical options rather than a brochure.