To check if your toilet is the culprit, the DWP offers free dye tablets that go in the toilet tank. Once the tablet is in the tank, wait 10 to 15 minutes and check the toilet bowl for color — color indicates a leak. For free tablets call (800) 544-4498 and press 5 or send an email to waterconservation@ladwp.com. You can also do this test with food coloring.