If your a tenant I would ask your landlord to get a sparky to change that, water heaters use a lot of power to be on a plug (although alot are) and that look near the end of is day..
Slip the sparky $20 whilst he's there to put in a double.
Yeah our sparky's aren't too bright and barely speak English so I have tried to stay away from dealing with them or letting them see what I have done with the sockets and the spare bedroom although I plan to redo this whole setup soon enough.
I was getting ready to order when I realized I will need an adapter for my extension cable or maybe rethink the entire setup. Can I plug my lepa's standard C19 to 5-15P cable into a drop cord then have the drop cord plug into a 5-15R to 6-20P adapter? or can I rig something similar? I'm thinking the power plugs may be on opposite sides and I know there is an amp disadvantage but I expect I will be under 10 amps easily with the efficiency increase?