Frontload GE Washing Machine to sit on Basement cement floor. Drain to Greywater rockbed is a 2" line going out through wall 54" above basement floor. It goes through wall and down approx 3 feet on a 45 degree angle to a 4" line which runs 40 feet to the greywater rock well. Can I and how should I put the washer drain into that 2" line? Where that 2" line goes out the wall it is only 24" below basement ceiling. If I raise the washer above the floor , how high should I go?
Washers are supposed to drain into a vertical standpipe 18-30 inches in height above a trap. The trap arm must then be vented before waste water can be discharged into waste piping. I don't believe there are lesser requirements allowed for greywater discharge. By the time this all is installed, the washer must pump up to within 6 inches of the ceiling. How high the washer can pump is dependent on the model. Once this height is determined, you can calculate how high the machine must be to meet all requirements.
As long as the discharge to the drain well is not shared with anything else, especially a toilet, I don't think there is any value or real need to have a P-trap, except maybe to discourage insects, rodents, and the like from coming into the house. Even that problem can be eliminated by sealing the washer hose coupling to the 2 inch line.
The GE WCVH6800J installation manual (page 18) says a standpipe of 24 to 96 inches above the floor is acceptable. So that model would be just fine in your installation. Check the installation manual for your model for authoritative verification.