Have you tried a Python? My tank is downstairs and I too have to use an upstairs bathroom to drain/fill my tank. You would have to use your sink rather than your tub, but I've found it's such a relieving alternative to the old gravity-vacuum-and-bucket method. Mine is 50ft long but I think they come in 70 or 75 ft too, if your bathroom is farther from your tank than mine is.
'Methinks that in looking at things spiritual, we are too much like oysters observing
the sun through the water, and thinking that water the thinnest of air.' - Herman Melville, Moby-Dick
29G freshwater tropical community tank