Help With Traps

[celticbhoy]

Hi.
I was wondering if someone can help explain the whole 'water-seal' part of Traps.
I just dont get it at all. Example, traps fitted on flat bottomed appliances should have a minimum water seal of 38mm.
Any help would be appreciated.

 

[dontknowitall]

Not come across this before but I imagine the 38mm refers to the depth of water from the level where it won't seal (ie leave an air gap).

Am I right in thinking this is part of a plumbing theory course/test? In real life I don't think this is an issue.

 

[GQuigley67]

why do you need to know ? this is only really relevant when doing drain testing as the size of your trap determins how much pressure you can put into the test. Basins and sinks are usually 75mm and showers are usually 40mm i cant remeber what toilets are

 

[GQuigley67]

as long as there is water between the air in the room and the air in the drain then you will have a water seal Google Image Result for http://rpmedia.ask.com/ts?u=/wikipedia/commons/thumb/f/fe/Ptrap.jpg/180px-Ptrap.jpg

 

[stevetheplumber]

why do you need to know ? this is only really relevant when doing drain testing as the size of your trap determins how much pressure you can put into the test. Basins and sinks are usually 75mm and showers are usually 40mm i cant remeber what toilets are

depth of seal is determined by where its running to for direct to soil you use deep seal and to gullies or hopper head shallows ok two piece low line bath traps are deep seal as the outlet height means your using part of the waste fitting as part of the trap
deep seal is usually 75mm shallow 40mm
wc pans are as cast not much you can do about them

 

[GQuigley67]

only time ive had to worry about the depth of a trap seal is when doing drain testing, otherwise its not really been a problem.

 

[nicro3]

Wc and Gully traps are unlikely to receive full bore discharge so seals can be shallower.

 

[celticbhoy]

Yeah, we got it given out at College and it confused me a bit. Ill have a look through the link and ask again if Im still stuck. Cheers.