S-traps self Syphoning

[Matt0029]

I watched a video and it went in about S-traps self spyhoning after discharge and said they were band in the USA. This isn't the case in the UK?

 

[Ric2013]

Not that I am aware. I think as long as you test that it works when installed and there remains a minimum of 25mm trap seal then you're okay.

However, if you look at ADH, it does show all basins discharging horizontally or at a slight angle which implies that that is how it should ideally be, and there is some kind of standard shown in my level 3 book which states that the amount of vertical section on a basin waste should be a maximum of... nil. In practice, if your only choice is to discharge vertically because your basin and soil stack are on different walls, you would have to have a vertical drop. I don't really see that a P-trap and bend adjacent or an S-trap straight into a vertical section are going to be any different.