I don't have a relief valve but that is possible, don't know. I just open another valve just barely if I need to give the motors a little more breathing room. In your case you could do that as well or if you're using all of the zones, you could then control suction by turning on/off motors. With the idea of keeping engineering simple, I would recommend removing the relief valve until you understand how the system operates since the relief valve is somewhat of a black box in how/when it operates.