The midfielder opened the scoring six minutes into the second half, latching onto a flick on by Sean Marks before bundling the ball into the bottom corner.
It was Tarpey’s fifth goal in a week having scored four in Maidenhead’s 5-0 win against Hemel Hempstead Town on Tuesday night and rounded off a poor afternoon for the Clarets.
Chelmsford failed to put former Claret ‘keeper Carl Pentney under any real pressure, not forcing the Maidenhead stopper into a meaningful save.
It was City’s second defeat in a week having lost to St Albans City on Tuesday and left Clarets boss, Rod Stringer less than impressed with his side, keeping them on the pitch for half an hour after the full time whistle had blown.
Looking for a reaction from that defeat at Clarence Park, Stringer made five changes to his starting line-up against Maidenhead who had won three of their opening four matches of the season.
Max Cornhill, Robbie Willmott and Mark Haines were all missing after knocks picked up on Tuesday, being replaced by Josh Rees, Luke Daley and Phil Walsh.
Frankie Merrifield and Jake Reid rounded off the changes for the Clarets with the latter making his first return to York Road having joined from Maidenhead in the summer.
Having won so convincingly on Tuesday, Maidenhead were unchanged and wasted little time in testing the hands of Joe Welch with a Dave Tarpey free kick inside the first minute.
The Clarets were lucky to get away with a poor defensive error when Ashley Miller failed the connect with his back-pass to Welch, putting the ball on a plate for Harry Pritchard who was unable to find the target.
Pritchard again came close just minutes later as Tarpey hit City on the counter attack. Being fed by Tarpey, Pritchard dragged a shot inches wide of the far post with Tarpey unable to tap home on the stretch.
Chelmsford’s best opportunities of the half came via Bagasan Graham who created the first chance before being on the end of the second late in the half.
The first came when Graham stole the ball in the middle and got himself into a crossing position having beaten Ryan Peters for pace. Graham picked out Jake Reid with his cross but the former Magpie failed to connect before Rene Steer cleared to prevent Luke Daley from having a shot on goal.
Then in first half stoppage time Daley managed to get beyond Steer to send a dangerous cross across the face of the six-yard box, it fell to Graham but his connection was poor, looping the ball up towards the far post where Miller was flagged offside.
Prior to the game Stringer was very clear with his side about the threat of the long ball into Sean Marks and Tarpey, but his words fell on death ears as that combination linked up to score what would turn out to be the winning goal.
A straight punt down the field by Carl Pentney was chested down into the path of Tarpey by Marks, leaving the in-form midfielder to find the bottom corner and break the deadlock in the 51st minute.
It was the fourth time in five games that the Clarets had had to come from behind to try and rescue something from the game and they should have equalised straight away through Frankie Merrifield.
Reid managed to muscle his way to the by-line picking out Merrifield eight yards from goal but the midfielder, who was making his full debut for the Clarets, appeared to be caught in two minds and neither shot or passed to the unmarked Graham before the move broke down.
Stringer didn’t hang around in making two attacking changes introducing Shamir Mullings and Shaun Jeffers, and the latter had City’s best chances to equalise although neither could be considered a clear opportunity.
Jeffers first caused a nuisance when he jumped up in front of Pentney after a Daniel Blanchett cross, causing the former Claret ‘keeper to fumble the ball just wide for a corner.
The second came from a quickly worked free kick from Chris Bush, which was played in Jeffers’ feet before the striker cut inside only to see his effort deflect over the top.
Maidenhead seemed content with their one goal lead, not really troubling Welch further although they did have a goal disallowed for offside after Pritchard’s cross was bundled in on the line.
It didn’t prove decisive though in the end for the home side as they comfortably held out to go top of the table.
1. Carl Pentney
2. Ryan Peters
3. Rene Steer
4. Kieran Forbes
5. Alan Massey (C)
6. Dean Inman
7. Dave Tarpey
8. James Comley
9. Sean Marks
10. James Mulley
11. Harry Pritchard
12. Charlie Wassmer (On for Kieran Forbes 60’)
14. Sam Barratt
15. Christian Smith (On for Dean Inman 74’)
16. Kyran Wiltshire
17. James Hammond (On for James Mulley 84’)
1. Joe Welch
2. Ashley Miller
3. Daniel Blanchett
4. Josh Rees
5. Chris Bush
6. Phil Walsh
7. Luke Daley
8. Anthony Church (C)
9. Jake Reid
10. Frankie Merrifield
11. Bagasan Graham
12. Shaun Jeffers (On for Jake Reid 54’)
14. Shamir Mullings (On for Josh Rees 54’)
15. Hugo Skepelhorn (On for Daniel Blanchett 74’)
16. Harry Morgan
17. Colan Balkwell
Maidenhead United: Dave Tarpey 51’
Chelmsford City: None
Maidenhead United: Alan Massey 59’, Charlie Wassmer 69’, Dean Inman 71’, James Comley 81’
Chelmsford City: Bagasan Graham 64’, Ashley Miller 66’
Referee: Gary Parsons
Assistant Referees: Stephen Graham & Martin Bloor
City Man of the Match: Bagasan Graham