#3 rebar is most commonly used to reinforce pools nationwide. Size and placement of reinforcing bars or rebars is critical to the structural integrity of your pool. We recommend at least #3 rebar on the vertical walls with 10" x 10" on center spacing with a tie at every intersection. We recommend #3 on the floor running the width of the pool and #4 running the length of the pool, again on 10" x 10" on center spacing with a tie at every intersection. In most cases there are needs for larger steel bars and tighter spacing as well as multiple layers or mats of steel.