Isn't there a real experienced master plumber on this forum board that could give a definitive answer to this problem of what to replace the leak prone valve with, instead of opinions and Mr. fix it ideas. I thought my Shark bite check valve idea was the simple answer but called Shark bite and their engineer said it will work UNLESS the part fails and you have clean water pressure on one side and dirty water pressure on the other side the dirty water COULD back up into the clean side and contaminate the water supply, like with a garden hose situation when yo release the handle on the sprayer you still have pressure on both sides of the valve. Hence the vacuum break part. But you will never have pressure greater than the faucet on the tank flush system side because it`s always open and unable to build pressure on the back side of the valve. So I think my cheap Shark Bite idea is good but maybe not the code way to covering ALL possible scenarios. I guess you could have clogged tank sprayer at some point and have pressure on both sides of the check valve and if it failed at that very moment everybody goes blind or dies.
