The Titans, chasing an unlikely 444 for victory, resumed on 62 for two and the cancellation of the gritty 53-run third-wicket stand happened six overs into the day when Rory Kleinveldt trapped Graeme van Buuren lbw for 23.
Piedt followed up immediately with the wicket of Qaasim Adams for a duck, but the resistance of Heino Kuhn (69) continued until two overs after the drinks break when seamer Dane Paterson had him caught in the slips by Justin Kemp.
There was obviously more determination in the Titans middle-order than in the first innings, when they lost their last seven wickets for 23 runs, as Mangaliso Mosehle (26) batted for an hour-and-a-half and Shaun von Berg dug in for nearly two hours as he also scored 26.
Roelof van der Merwe was the best of the Titans batsmen on the final day, however, as he scored 51 in 128 minutes of resistance, but it was never going to be enough to avoid a heavy defeat for the visitors.
Piedt produced a top-class display of spin bowling in helpful conditions as he took six for 100 in 34.2 overs, while Kleinveldt chipped in with two for 55 to finish with a nine-wicket haul from the match.
In Johannesburg, a brilliant all-round bowling display by the Knights forced the Highveld Lions batsmen to sell their wickets cheaply, but it wasn’t enough to secure victory for the Central franchise as bad light and rain left them to accept a draw.
The Lions had resumed their first innings on 54 for two, but the excellent, probing bowling of the Knights pacemen enabled them to tear through the home side’s batting line-up, dismissing them for a paltry 121 on the stroke of lunch.
Quinton Friend ran through the lower-order to finish with four for 35 in 13 overs, but it was cunning fast-medium bowler Malusi Siboto who made the most telling strikes by removing Devon Conway (10) and captain Stephen Cook (45) on his way to fine figures of two for 17 in 12 overs.
Off-spinner Werner Coetsee then struck twice in 14 balls to finish the Lions innings.
With the Knights bowlers getting the most out of a Wanderers pitch that was producing some tricks, the Lions were under pressure to save the game as they came out to bat again after lunch in their follow-on innings, trailing by 208 runs with 72 overs left in the day.
Fast bowler Corne Dry then produced a vituperative opening spell in which he took two for two in six overs, having both Cook and Dominic Hendricks caught by the sharp Rilee Rossouw in the slips for five.
Temba Bavuma saw off the pacemen for the next hour, but Knights captain Coetsee dismissed him with his first ball in the second innings. The diminutive batsman had scored 25 when he pushed forward to a delivery that had some air, edging a low catch to slip which Rossouw nonchalantly claimed.
Neil McKenzie batted for 80 minutes with grim determination, scoring just three off 50 balls, while Conway joined him for half-an-hour, taking the Lions to 54 for three before the weather turned for the worse for the Knights.
Dark clouds first of all forced the players off for bad light at 2.50pm, followed by torrential rain which caused the match to be called off.
The Dolphins were also unable to administer the killer blow to the Warriors due to bad weather at Buffalo Park in East London.
The Dolphins declared their second innings on their overnight total of 257 for eight, a lead of 356, leaving the Warriors to bat out 96 overs on the fourth day.
The Dolphins looked about to run through the home side when lunch was taken with the Warriors on 70 for three, with Robbie Frylinck taking three for 20.
But rain began falling during the interval and at 2pm what seemed a rather rushed decision to call off the game was made.
Opener Michael Price (37*) and Colin Ingram (12*) had batted most sensibly to take the Warriors from 30 for three to their lunchtime total.
The Cobras’ victory deals a hammer blow to the other teams in the four-day series as it means they now lead by 17 points with three rounds remaining.
The Knights are in second place, while the Dolphins have moved into third, managing to overtake the Lions, nearly 11 points behind the Central franchise.
The loss, their fourth in seventh matches this season, has condemned the Titans to the bottom of the log, trailing the Warriors by two points.