Wastewater adapters - he-ruide
If you cannot find a unrestricted Y connector you can make one your self.  The parts are:
1. One 1 inch PVC "T" with threads
2. Three 1 inch male threaded to 3/4 inch female threaded PVC coupler
3. Two 3/4 inch male to 3/4 hose male brass couplers
4. One 3/4 inch male to 3/4 hose female brass coupler

If you cannot find a unrestricted Y connector you can make one your self. The parts are:
1. One 1 inch PVC "T" with threads
2. Three 1 inch male threaded to 3/4 inch female threaded PVC coupler
3. Two 3/4 inch male to 3/4 hose male brass couplers
4. One 3/4 inch male to 3/4 hose female brass coupler