looking for pressure vessel or large pipe

[gsanocki]

I am thinking in the next year or two of building a set of large land rollers for rolling fescue plowing, I will need 3 rollers about 12-16 foot long. The sets I have rented have 36 inch rollers and about 3/8 or slightly larger wall thickness. I would like the rollers to hold a bit more water and have a bit thicker wall as my rocks do bend the 3/8 walls. One thing that crossed my mind was reject pressure vessels like old nh3 tanks . I was wondering if anyone knows how thick they are and where there might be some lieing around that I could get fairly cheap. Thank you Gary Sanocki Eaglesham, Alta