I'm doing a job in a plant. The job is inside of a cooling tower. We are changing out all of the girts(2x4's), but they don't want to change the columns(4x4's). The plant supervisor said that they expect what we are doing to this unit to last another ten years. In my opinion that would be ok if you were changing everything. My question to this dilemma and to ease my mind is does anyone know how long a new, treated 4x4 post last in constant water? I think they'll be coming back in another 2-4 and changing out the 4x4's. Oh well, it ain't my money they are wasting!!