This is probably a completed stupid question to those in the know.
I am cuurently renewing my bath and have bought a pop up waste to go into it. Having thought about the type of trap to fit i thought the best for ease of maintenance would be a bottle trap, as i have plenty of space within the floor joists.
When i offered up the trap to the threaded section at the bottom of the pop up waste the trap thread was too small.
Although i have never seen a bottle trap waste under a bath.
Are the likes of the shallow bath trap a bigger size?
My other reasoninhg behing the bottle trap was the increased depth of seal. Although at the moment it only goes into a gulley, in the future it could possibly get rerouted into the stack.
Probably not much reason - apart from space, I haven't seen many where you could fit a bottle trap in (unless you cut the floorboards to accomodate it, but then easily removal becomes more difficult) the shallow bath traps are designed to fit between the bath and the floor.
At the end of the day whether a bath trap or bottle trap is used - it's going to do the job.
Thanks again, my bath is a free standing thing and the waste would only be accesable via the floor boards anyway and then the trap would be at arms length away down the joist run, so i think i will go for the bottle trap as i have enough room in the joist space.
For baths you should have a trap with a water seal of 50mm minimum. Usually with shallow traps you end up with a 38mm water seal, so it is best to make sure if you are buying a trap that is less than 50mm that you buy one that is an anti syphon version.