A month ago I had a post of how do you get a 1/4 inch drop to your initial hook up of a toilet flange (which is level with floor and toilet) and 90 degree 3" or 4" ABS connected to that same flange. I have been told (including a prior post) and other sources that it is in the 90 degree bend because it isn't actually 90 degrees (with a drawing to support it). There are a few types of 90 degree bends, long, short, and a "closet ell". The closet Ell has a female end of bend on one end, and a male end on the other end of bend (which some stores call a street elbo). My questions are: 1) Which 90 degree (closet Ell, short bend, long bend) do you use with the toilet flange so you will get that off set 1/4 inch drop per foot? 2) If the closet Ell is the one that has the 1/4 inch drop in conjunction with a toilet flange how is it used; Example; is male end of bend connected to toilet flange??

You do NOT really have to worry about it, because the hubs, once the glue is applied, will allow the pipe to flex to give you even more than the required pitch.

All the 90* elbows you listed, long/short/closet are slightly greater than 90* to automatically give you the slope you are looking for.

Here is the calculation. If x denotes the angle, in degrees, by which the elbow angle exceeds 90*, then tan x = (1/4)/12 =0.0208, leading to x = 1 1/5 degrees. Thus the 90* elbow is actually a 91 1/5 degree elbow.

George - did you mean to say less than 90°?

Steve, you have a point. I was referring to the included angle between the two arms of an elbow but that is not how we specify an elbow, we look at the bend it provides.

So, a 90* elbow is actually a 88 4/5* elbow.



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