West Brom still need a fortunate combination of results elsewhere to take their fight into the final day at Crystal Palace.
Jake Livermore had given Hull the lead by finishing off a counterattack in the 28th minute, but Vydra equalised in the 86th with his first goal for the club to end a four-game losing streak in the league for the Baggies. The Czech striker is on loan from Udinese.
Hull went ahead after Jake Livermore's shot from outside the area took a deflection and looped over Liverpool goalkeeper Simon Mignolet in the 20th minute at the KC Stadium.