i think by "it" neal means a roof vent immediatly down stream from pump. That "sure vent" or other maker's similar product would be a stop gap measure or if there is no way to properly vent that line. The back up into tub hints that the bathroom has venting problems and/or that the line past the tub is clogged. Many new washer do not have a lint filter anymore, that's all well and good for newer drain lines, but the lint can build up in older lines, combined with grease from kitchen and bath lines a clog can slowly build up. i have kitchen sink and dishwasher that drains down to washer connection, had sporadic clogs, got new washer with no lint trap, clog became almost annual hassle.
What else drains into the line before or shortly past that tub and toilet?
[CENTER][FONT=Comic Sans MS]Measure twice, cut once.[/FONT][/CENTER]
[CENTER][FONT=Comic Sans MS]Look at the nail, not the hammer. Watch the fence, not the blade.[/FONT][/CENTER]
[CENTER][FONT=Comic Sans MS]If you hook your thumb over your belt you won't hit it with the hammer or leave it layin on the saw table.[/FONT][/CENTER]