Plumbing leak help

Lynnmor wrote:

dougrainer wrote:
The purpose of this check valve is to keep from siphoning black water out of the tank. It is mounted HIGHER than the tank system. 99% of these valves are located in the Bath Lavy sink area. They leak from a few things. BUT THEY ARE NOT SUPPOSED TO LEAK AT ALL. The plastic Check valves do not like high water pressure, especially if you open the fresh water spigot full force. Always start out with a slow opening of your fresh water spigot, then increase to full force. They also leak because people FORGET them when winterizing. They will freeze and then blow water out the next time you flush. I advise to use a BRASS check valve instead of the plastic valves. I cannot remember if I ever had a brass valve leak or fail at all. You can put a standard 1/2 inch check valve in place if you do not want the vented type that comes standard. I believe the Vented standard ones are required by code. Doug

Copy & paste from the instructions for the most popular model:

The atmospheric vacuum breaker shall not be installed where the venting of water from the device during the normal functioning causes damage.