Is a 3 way valve needed if your installing Last Step Chemical Injection to a General Pump to bleed the chemical system? So far I have purchased a General Pump Pulse Pump part#100906 and the pulse pump adapter. My machine already has a Dwyer meter. Do I need an additional check valve as well? Suggestions on how to plumb this would be appreciated. Other ideas? Machine is a 2015 EZ3547. Thank you!