The hosts were without leading marksman Ethan Prichard again, on trial at Bolton before doing the same at Wycombe Wanderers, and Kaleem Haitham who scored the winner against Ashford United last time out.
So, Isaac Bello started instead of Haitham in an otherwise unchanged XI.
Chi began brightly and Rob Hutchings got sent down the left to deliver.
Clarke then picked up the first of a catalogue of fouls on the night in the third minute before super vision from Rowlatt led to a through ball which Bello couldn’t quite control.
Next, after good work by Rowlatt and captain Josh Clack, only the frame of the goal denied Clarke from putting the home side ahead.
Harrison Parker then did well to beat Bello to the ball and shepherd it out for a goal kick.
A poor cross-cum-shot by Clack caused Matte Pierson little trouble; Connor Cody was impeded; and a short corner fell to Wasps skipper Glenn Wilson which the home team smuggled away.
And then Clarke broke the deadlock powerfully heading in an inviting Hutchings’ cross.
It might have been 2-0 moments later when Hutchings latched on to a Lewis Hyde ping.
EG gave Chi a few problems of their own as Ryan Green, Junior Savane and Max Walsh linked up but the back four cleared.
Pierson then recovered and got to the ball at the second attempt ahead of Clack.
Tom Summerfield had a go with a snap shot at the mid-point only for a Chichester defender to concede a corner.
Hutchings won one at the other end on 23 that was punched away and Cody earned a subsequent corner which Hutchings whipped over too deep.
The Chi left back wasn’t far off with a fierce effort following a super take by Clarke before a delicious back heel by Clack into Joe Moore’s path permitted the youngster to carve open the middle of the park.
Ben Aubrey appealed for a penalty after Hyde challenged him in the box.
Pierson gathered Clarke’s deflected effort on 33 and referee Joel Lamping waved aside Chi claims after he was brought down and Clack’s follow up was saved.
Emmett Dunn spurned a free header from the resulting corner before Moore was well-in on Harrison Parker.
Clack had a shot when he probably should have rolled a square ball to Bello and a goalmouth scramble ensued after Tariq Straker struck the underside of the crossbar but the hosts eventually snuffed out the danger.
A nasty foul on Bello by Straker had the Oaklands Park faithful rightly baying for blood – a yellow card Mr Lamping’s odd decision.
Chichester won a couple of corners which came to nothing before the half time whistle went.
Bello was replaced with Olly Munt at the interval who found an offside Clarke seconds after the re-start.
And then Matt Astle spurned a chance with a wayward shot after Parker’s throw-in.
Ten minutes or so in Rowlatt was instrumental in a move that set Clack up but the No7 couldn’t finish.
Pierson claimed once more as the ball bobbled around and Chi had defending to do when East Grinstead pressed – Moore’s block was superb to deny the visitors in the area.
Next, Clack inadvertently gave a corner away on the hour mark which Green headed off target.
EG rang the changes with Andrew Briggs and Lamin Bah coming on for Tom Cooney and Savane, and Summerfield joined Straker in the notepad.
Rowlatt carved things up on 69 and rifled the ball into the back of the net to double Chi’s lead with a wonderful strike.
Multiple yellow cards were brandished after a skirmish on 72.
Then Rowlatt burst through again and Hutchings fired an effort just over.
Dunn had an attempt deflected and punched clear and Walsh ballooned a shot high as it got end to end in the last five.
So, Chi put that March run of one point from a possible 21 behind them with a second clean-sheet on the bounce.
Miles Rutherford’s men move up to 10th spot and travel to Sevenoaks for their last game of the league campaign on Saturday 22nd April (Kick Off 3pm).
Chichester – Magee, Cody, Hutchings, Moore, Hyde, Pashley, Clack, Dunn, Clarke, Rowlatt, Bello (Weinberger, Munt, Montague, Davidson, Haitham).