What kind of 4" 3-way valves are available (for gray water system)?

How can I selectively redirect a 4" pvc pipe into either of two other 4" pipes? Its going to hold gray water only, no sewage. I've looked at Jandy valves, nothing in 4". There are 4" PVC ball valves, would these be ok?
I'm going to route all of my sinks and showers, etc, into a 4" PVC pipe, which will parallel the existing sewage pipe in the basement. I want to be able to choose manually whether to route it into a gray- water system, or the septic system. There are two 4" PVC pipe a few feet apart where they go through the wall, so the new gray line will go through a Y-valve of some kind and into one of these two outlet pipes.
I am assuming, if I can't get a 4" 3-way valve, then a pair of regular PVC ball valves would be adequate.
Thanks for any tips!
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