11-21-2005, 07:18 PM
dave, we have alot of earthquakes(small ones)and so far i only have one small crack in my cement ring. i believe the cement ring is the way to go, it stablizes your pool better, it also gives you more gallons than if you were sitting on the ground because it's like a cone inside the ring. the 18' diameter pools will give you 10,000 gallons.