Discuss What waste to use for basin and vanity in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

chris watkins

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Bottle trap, 1.1/4" with 75mm water seal. Short piece of 32mm pipe then increase to 40mm into a bend or tee. That way minimal risk of siphonage.
 

Ben-gee

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Personally prefer p-traps, deep seal bottles are usually bulky and flow rate is slightly worse too.

I have found in some units with semi-recessed basin the bottle traps foul on the unit fascia, as the trap is symmetrical they come forward too far. The p-trap can be arranged to go fully backwards .

I do use the shallow seal bottle traps sometimes if it’s going into hopper/gulley as they are quite neat.
 

chris watkins

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These can be useful if there's not much space behind the pedestal, only if your waste pipe is low enough to connect to with this design though.

https://www.screwfix.com/p/mcalpine-pedestal-trap-white-32-x/30503

What do the others on here think of this type of pedestal trap, yay or nay?
It will siphon the water out every time the basin is used thats what I know,
but Paul is fitting a vanity basin not a pedestal, so he won't have to worry about space.
 

Stigster

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I do a trap seal loss task with our students and do see that they are more easily syphoned but that is with my horrid "worst case scenario" setup where I have three basins connected to one 1 1/4" pipe on an excessively long run. Then the pedestal traps fail the tests where a bottle trap does not, not that I would use a bottle trap on a basin generally. A P trap also loses its seal in these tests.

When I set it all up properly with a correctly sized waste pipe, proper fall and distance to an open vented stack, the pedestal traps do not fail.

I suppose we have to assume that the trap could be installed in a badly designed system and then I am sure syphoning will be a problem. I do wholly accept that the pedestal trap is the most sensitive to syphonic action for sure though.
 

chris watkins

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I do a trap seal loss task with our students and do see that they are more easily syphoned but that is with my horrid "worst case scenario" setup where I have three basins connected to one 1 1/4" pipe on an excessively long run. Then the pedestal traps fail the tests where a bottle trap does not, not that I would use a bottle trap on a basin generally. A P trap also loses its seal in these tests.

When I set it all up properly with a correctly sized waste pipe, proper fall and distance to an open vented stack, the pedestal traps do not fail.

I suppose we have to assume that the trap could be installed in a badly designed system and then I am sure syphoning will be a problem. I do wholly accept that the pedestal trap is the most sensitive to syphonic action for sure though.
Are but your traps & wastes are all clean & not been reduces in bore by years of usage, thats the problem with doing things in colleges instead of real life.
 

Stigster

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Are but your traps & wastes are all clean & not been reduces in bore by years of usage, thats the problem with doing things in colleges instead of real life.
Yes they are clean, apart from when I put sand or other things in them to create blockages but you do have a valid point there. College is just a starting point and nothing beats real life experience I totally agree.

I have to say I've not come across many if any at all in service as the good old fashioned P trap does a fine job in the vast majority of situations.
 

ShaunCorbs

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Small bottle for me as sometimes they hit the shelves / draws
 

Stigster

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I am a P trap man myself, with exception of bottles on basins if you must. ;)
The bottle trap is easy for the customer to open and clean at least. Also, in my tests the bottle traps are almost impossible to syphon to the point of seal loss too even when I'm trying to make it do that.
 
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