^^^ I have these exact steps. I've seen the link here by (Anna, I think?) that explains how to fill and cap 3" pvc pipes and weigh down the steps. I've made 4 of these 3" pipes and filled them with sand and tied them with nylon ties.
The steps are still floating up. Do I just need more sand filled pipes? How much weight does this actually need? I've used one bag of 50 pound sand. Not sure how much more I can fit under there comfortably. Right now I laid another 50 pound bag of sand on top of the top step and it's holding... I think.
2 pieces of 3" pipe x 28" long
2 pieces x 16" long