If I'm using 5,500l/h, I'll use 32mm pipe liao or 2 x 25mm pipe. I prefer to have unobstruct flow of water to the sump.
My pipes from overflow initially is 20mm (short distance), then increased to 25mm. My water flow is 2500l/h.
For your return pump, u can use 13mm for 2,200l/h or 20mm for 5,500l/s