Errr, sags in what?. what is meant by "too strong"? "figure the sag at a tie in"??

Maybe it's me, but this question doesn't make sense I'm afraid. More explanation, less jargon and a drawing might help

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

a sag is when you bend a pipe down in order to fit the contour of your ditch you are putting into. when you run your pipe across the pipe line you install up to and going away from a creek. when you are ready to install in the creek you first have to figure the sag to bend to in order to meet both ends perfectly and weld it in position. this is called a tie in. when it is bent too strong it means the bend is too sharp and the ends do not meet.

I kind of knew all that, but at least we're now in common understanding.

sounds like you need a better surveyor then plot it on a section drawing and hey presto - a design that works.

Doing things "by eye" will get you so far, but where you bend further and go deeper, then you need to do it better.

sounds a little like someone is simply taking horizontal distance from one tie-in point to the other and ignoring the impact of the vertical leg?? Small deflections you'll get away with it, but I guess creeks are deeper and hence more impact on horizontal length

Kind of difficult to see without pictures or drawings. If it's consistently short, then add some green lengths to your sag design to compensate?

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way