Bachmann was at fault for both Leeds' goals as they raced into a 2-0 lead inside the opening seven minutes at Elland Road.
Largie Ramazani and Brenden Aaronson were the Leeds goal-scorers and although Kwadwo Baah pulled one back for Watford, the hosts held on for consecutive home wins in the space of five days.
Daniel Farke's side extended their unbeaten league run to six matches and have lost only one of their first 11 games.
Watford slipped to a fifth successive away league defeat on the back of their 3-0 loss to arch rivals Luton last weekend.
Shane Duffy ensured Norwich made it six matches without defeat as they fought back from two goals down to draw 2-2 at Preston.
Sam Greenwood's sixth-minute penalty put Preston in front and Duane Holmes grabbed a second for the home side six minutes later.
The Canaries rallied as the terrific Borja Sainz pulled a goal back in first-half stoppage time and Duffy bagged the equaliser after 61 minutes.
Dane Scarlett scored for the second successive game as Oxford rescued a 1-1 draw with Derby at the Kassam Stadium.
Nahki Wells bagged a quick-fire double as Bristol City hit back to draw 2-2 at Stoke.
Lewis Koumas and Andrew Moran put Stoke two goals ahead inside the opening 15 minutes.
But a brace from Wells early in the second half hauled the Robins level.
The draw extended Bristol City's unbeaten run to six matches as they continue without boss Liam Manning following the death of this son Theo earlier this month.
Cardiff climbed out of the relegation zone with a 2-0 home win against Portsmouth.
A Regan Poole own goal and Callum Robinson's close-range effort put Cardiff in command after just 13 minutes.
Swansea's winless run extended to five matches after a 0-0 draw at Sheffield Wednesday, while Coventry drew 1-1 with fellow strugglers QPR at Loftus Road.
