What danb and Jop are saying are very correct.

Dear dsiingh,

Pls use the following formula for claculating the delection for same span of small and large bore pipes (of your requirement) continuously supported:

D = 5wL^4/384EI

where
D = defelction
w = weigth of pipe (filled or empty) per unit length
L = distance between two adjacent supports, i.e. span
E = elastic modulus of pipe mateial
I = moment of inertia of pipe

From the above you will easily find that for same value of L, D would be higher for smaller dia. pipe.