Long 2" 90 vs Extra long 2" 90 for drains.

[MAYOR]

Hi There,
Looking to learn about 2" 90s for drains.
I was at Lowes today and notice that there is a short 90, long 90 and an extra long 90 all 2" abs.
I guessing the short 90 is only meant for venting.
Where would one us the extra long 90 vs the long 90?
Thank you
Mayor

 

[Terry]

From vertical to horizontal, long turn 90
From horizontal to vertical, you can use a medium 90
Horizontal to horizontal, long turn 90's or 45's

And then there are vent 90's with no sweep at all. I don't even have these on the truck. You will notice those sell for more, and there is no advantage to have a fitting with no sweep.

Vertical waste into a horizontal line, would be a wye or combo fitting. A santee on it's back can't receive waste from above.
A horizontal trap arm to the vertical vent uses a santee. A wye would allow the trap to siphon dry and you don't want that.

 

[Sponsor]

 

[Jeff H Young]

When I first started plumbing we used vent 90s couple years later doing my own work I found out vent 90s were like double 1/4 the price of 1/4 bends I liked using them but never went back to wasting money and stocking an extra fitting