Our very old concrete pool was leaking all summer and we took a chance and bought this material. We were able to seal the cracks with this putty and it stopped the leak for more than a month. We did have to add more putty to the cracks after vacuuming the spot a few times as this pulls the putty out after a while, but it was definitely worth the money! We apply every month or so and it saves us tons of money on water!