The goal was a cruel blow for a United side that showed a positive response to their previous league defeat against Hassocks the previous Saturday.
Aaron Capon was the only change to the side that started against Hassocks, replacing Peter Cooper who was joined on the substitutes bench by Jason Taylor and the returning Wade Eason.
Despite a strong start to the game, United were indebted to the post for keeping the scores level as Elliott Thompson saw his effort ricochet off the upright and across the goal to safety.
Lucas Mann, playing as a sole frontman, saw an early effort saved following a break down the left wing from Capon.
United had a strong shout for a penalty turned down on 25 minutes when Capon's path to goal was blocked by two Dorking defenders whilst the winger was in full flow.
Mann has arguably the chance of the first half just before half-time, but the 10 goal striker dragged his effort wide. At the other end, the defensive pairing of Adam Davidson and Mike Gardner held firm to deny the leagues top scorer, Tom Tolfrey, with Tolfrey restricted to half chances.
The recent poor weather began to take effect on the playing surface, with players beginning to slip and the pitch cutting up, but ten minutes into the second half United took the lead.
An angled ball caught out the home defence and the jet-heeled Capon found space in behind to calmly slot the ball past Adam Faith in the home goal.
The goal prompted an immediate substitution from Dorking, with striker Charlie Pitcher brought on.
United captain Adam Davidson came perilously close to his first goal of the season as he unleashed an effort from 25 yards that whistled past the post.
Pitcher dragged an effort wide five minutes after his introduction, as Dorking began to apply pressure on the United defence.
The final 15 minutes saw Dorking bombard the United defence, but Davidson, Gardner and co held firm to thwart the home attacks.
Cooper and Taylor replaced the tiring Mann and Capon with five minutes to play and the substitues combined on 89 minutes to give United a chance for a second goal, but Taylor's effort was saved by the feet of Faith.
In the fourth minute of time added on, United's resolute defence was breached when Pitcher muscled past Brad Lewis and rifled an effort past Russ Tanner.
Many thought that would be the last action of the game, but there was still time for Dorking to launch one last attack as Tanner preserved a point for United as he got his fingertips to a curling effort from Pitcher that rebounded off the far post and was cleared to safety as the final whistle was blown.