If you notice that your pool suddenly started leaking alot, the first thing to check is the multi port valve. The seal inside the valve can fail and the water will pump right out the waste line.
This is a simple repair, you can pick up a new seal at your local pool store or have their service tech change it. One way to avoid this problem is to install a shut off valve on the waste line. This $10.00 valve can save you hundreds.