The four stricken youngsters were proving hard to reach after they were swept through a gap in the drain cover on a pond at Moor Park on Friday, July 8.
The animal charity was contacted after their anguished mum was spotted by a member of the public circling the drain.
At first, RSPCA Inspector Carl Larsson and Animal Rescue Officer (ARO) Daniel Tomlinson tried to grab the ducks with reach and rescue poles along with nets, but this rescue method proved tricky.
So the pair hatched a plan to flush the ducks to safety with help from city fire crews.
You can watch video of the rescue in our our media player above.
Daniel said: “We rang Lancashire Fire and Rescue Service for help and firefighters brought along a selection of hoses to choose from for the tricky task. The idea was to blast water through the drain via a manhole cover about 10 metres away.
“The hope was that the ducklings would shoot out the other end. We spent a couple of hours using different bits of kit, but we just couldn’t get to them.
"There was a tube at the bottom of the drain and when we got a net down to it they kept swimming out of reach.
“We’d tried everything we could to get them out and our colleague, ARO Nick Green, spent some time the night before trying as well.
“But once the water was pumped through the ducklings rose to the level of the water course and we were able to reach them one by one through the gap.
"It ended up being a bit like an extremely difficult game of hook-a-duck.”
Happily, the ducklings were none the worse for their ordeal, despite being trapped in the drain for at least 24 hours.
Daniel says it was fortunate their predicament was spotted in time as he suspects other young ducks might have slipped through the same gap in the grill, but sadly without being retrieved
“The gap is big enough for a duckling to get through, but not an adult duck. The local council has been contacted about it, but it is still a problem when the water level rises around the drain cover,” added Daniel.
“The fire service was absolutely incredible and we can’t thank them enough for their time commitment and equipment. We all spent hours problem-solving before, eventually, I pumped the water through one end of the drain while Carl retrieved the ducklings at the other end.”
The officers spent much of the day on the rescue on Friday, July 8 before Inspector Larsson was able to release the ducklings back onto the pond where their mother was waiting to greet them, with the moment captured on film by his colleague (see video).
The imaginative rescue comes as the RSPCA launches its Cancel Out Cruelty campaign, to raise funds to help its rescue teams out on the frontline continue to save animals, like these ducklings.