Tony Burman’s side travelled to Twerton Park on Saturday, starting the match with an unchanged eleven from the week before against Tonbridge Angels.
The bench was made up once again of Tom Wynter, Ellis Brown, Lee Noble, Ronnie Vint and goalkeeper Tony Coxall.
Both sides created their fair share of chances but neither provided any class up top until Wanadio bent in the winner six minutes from time.
Up until then the Romans had seen decent opportunities fall their way and they should still have snatched a point when George Rigg missed the target with a stoppage-time volley from six yards.
Marvin Morgan skinned Keaton Wood with a dummy, charged away down the left and set the ball back for Nick McCootie, who jabbed well over the top.
Duane Ofori-Acheampong sent an awkward header comfortably back for Max O’Leary in the away side’s first notable foray forward.
A tidy move deep in the right hand corner between Ryan Broom and the overlapping Rigg led to the latter swinging over a far-post cross that Morgan glanced wide under pressure.
Yet City were given a huge let-off at the other end after some shambolic work at the back.
O’Leary nipped out of his box after a weak backpass and clipped a nice ball across for Monthe, only to see his centre-half miscontrol and allow Andy Pugh in behind.
One-on-one with O’Leary, Pugh elected to square the ball for Ofori-Acheampong, but sent it straight over the byline for a goal-kick.
Dartford pressed the City backline at any chance, with Chas Hemmings the next victim down in the left corner as Of0ri-Acheampong hustled the ball away and set up a move that ended in Ryan Hayes hitting a first-time shot straight at O’Leary.
They got a taste of their own medicine when McCootie poached the ball off Tom Bonner, but with an awkward bounce he could only bunt a left-foot volley into the floor and wide.
Darts keeper Deren Ibrahim was finally drawn into a couple of saves when a Hemmings free-kick had him sprawling to his left, while Morgan found a way in behind and was thwarted by the onrushing custodian.
A darting 40-yard run by Wanadio could not be matched by his final shot, before the Romans got the last chance of the half.
Billy Murphy curled in a delightful cross from the right and to the far post, where Diallo could not collect cleanly from four yards out.
The visitors came out lively after the interval. Pugh found himself in another excellent shooting position when collecting a skilful flick from Ofori-Acheampong but shot across goal and straight to Hayes, who repeated the feat from the other side.
For the most part City held out and by the hour-mark the game was on a fairly even keel again, although the only shot in anger they had saw Broom fire straight at the feet of Ibrahim.
For Dartford, Ofori-Acheampong was played in from a neat move and scythed an effort well clear of the crossbar.
O’Leary appeared to have saved the game for City with a superb reaction save after Wanadio had crossed for Elliot Bradbrook.
The visitors eventually got the winning goal in the closing stages as the Romans gave the ball away yet again, allowing Dartford to piece together a fast, incisive break that ended with Wanadio bending a perfect shot across O’Leary.
However, City should still have come away with a point when Broom worked space on the left and crossed for an unmarked Rigg to slap into the side netting.
Bath City: O’Leary; Rigg, Hemmings, Monthe, Ball; Artus, Diallo, Murphy (Marshall 71); Broom, Morgan (Hunter 60), McCootie (Bowman 76).
Subs not used: Hutchinson, Batten.
Dartford: Ibrahim; Harris, Wood, Bonner, Gardiner, A Brown (Noble 63), Hayes (Wynter 78), Bradbrook, Ofori-Acheampong (E Brown 92), Pugh, Wanadio.
Subs not used: Vint, Coxall.