This is the seventh consecutive defeat of Norwich City coached by Daniel Farkke, and it was achieved thanks to a quad of the guest player Michael Antonio, two goals in each half.
The defeat left Norwich City in 20th and last on the list with 21 points, 13 points behind Watford, who are 17th, who beat Newcastle United 2-1 before the last three rounds of the season.
Antonio, 30, posed a constant threat to the defense of the hosts because of his permanent presence in their penalty area, becoming the first West Ham player to score a quad in one league game since 1981.
West Ham United are 16th on the list, six points above the relegation zone, and have a goal difference over Watford next.
In another match, striker Troy Denny scored two penalty kicks to lead Watford to a 2-1 victory over Newcastle and his second consecutive Premier League victory.
The victory gave Watford an important boost in the escape flight from three rounds before the end, and his score became 34 points in 17th place, a difference of six points from Bournemouth, who is sitting at the beginning of the relegation zone, which has an additional match.
The players paused a minute of silence before the start of the match to mourn the death of Newcastle United and Ireland coach Jack Charlton, who won the World Cup as a player with England and died at the age of 85 on Friday. The players wore black armbands, too.