Fluidmaster would like the opportunity to provide help. We suggest checking your refill tube position, if you have the refill tube shoved down or placed inside the overflow pipe pull it out and reattach to the overflow pipe using a refill clip. This will stop a siphon from occurring and stop the leak. Another area to check is the flush valve lock nut. You may need to tighten ½ turn beyond hand tight to stop the leak. If you need help with your installation or have any concerns contact Fluidmaster’s Technical Service Department as we are available Monday through Friday from 5:30 AM through 5:00 PM Pacific Standard Time. Contact options include: Chat www.fluidmaster.com/support E-Mail techsupport@fluidmaster.com and Toll Free 800-631-2011.