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p-trap or s-trap

Posted by Mark on December 13th, 2000 08:44 AM
In reply to inadequate vents by bc on December 13th, 2000 01:00 AM [Go to top of thread]

1 of 2 people found this post helpful

I have been looking for information and cannot find a clear example of an s-trap. I guess that the difference between the two is that a p-trap has a horizontal trap arm directly after the trap and an s-trap goes directly into a vertical pipe. I assume the problem is with velocity of the water being drained. In case of the kitchen sink, with the trap directly under the sink as normal and then a 2 and a half foot drop before a vent pipe joins would cause the water to reach such a velocity in that vertical 2 and a half feet, that siphoning would occur.In the washing machine, with a 4 foot drop down to a vented p-trap under floor, again the initial 4 foot drop would allow the water to reach such a velocity that the trap would be subject to siphoning. Is this the problem (regardless of whether the vertical drop is before or after the vent)? If it is, could I install a 90 degree elbow to slow down the vertical drop of the water?
(FYI: I am building my own house myself in a country that does not have vented plumbing - one reason for building my own house. Therefore I cannot have a pro. install the system and I have no one with the know-how to ask questions. Also: both washer and kitchen sink are under windows which the vent pipe must circumvent. Due to length of horizontal run, I would need a 2" vent pipe in these exterior 2x4 walls. These quadruple studs beside the windows are also where my seismic anchors attach and I would seriously compromise the integrity of these walls by notching or opening a hole in the studs.) Would a loop vent for an island sink application work? Thanks for valuable information.

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