I'm not sure I follow you completely but for what it's worth...
I installed a hot/cold water bypass valve to get low gravity flow between the hot & cold water line in a distant bath. The valve includes both a balancing valve and a check valve. The original one did not have the check ball and I did get some back flow - manufacturer indicated they had some get out incomplete and replaced it at no cost - worked fine after replacement.
See http://www.pumpsetc.com/aqualink.htm for info
Hope this helps