Are you talking about sodium bentonite? I love the stuff. Haven't used it for a leak- but I have it around my waterfall and also rebuilt an edge with it. There are a few sites about sodium bentonite and also the product bentomat. This is sodium bentonite woven with fabric- they use it to line landfills and huge ponds. Haven't found a supplier though. Tidy Cat unscented clumping cat litter is 100% sodium bentonite.