[RMcNeal]

It's only real purpose is to prevent any black tank contents from entering the fresh water supply and to provide a vacuum break to relieve pressure when the flush is not running.
Both of these functions can be accomplished with a hose end back flow preventer/vacuum breaker on the inlet in the wet bay.
It is extremely unlikely that it could happen anyway, but for just a few dollars you can add the back flow preventer in the wet bay and it screws right into the inlet where the hose screws in.
In my case, the valve was plumbed under the bathroom vanity sink, so I just followed the pipes into the basement, cut the elbows out that sent the pipe up to the valve and back down again and connected them at that point. You could even use a shark bite coupling if you don't have a pex crimping tool, but I prefer to crimp the connections.