Three bogus callers scammed a 62-year-old man from Portslade by pretending that they had called to unblock his drain.
It was one of two cases involving doorstep conmen in the same area on the same day.
Sussex Police said: “Police are issuing a warning after two linked frauds in Portslade where the victims were targeted by fraudsters pretending to be from Dyno-Rod drain company.
“A 62-year-old man in Foredown Road, Portslade, received a knock on the door from a stranger on Friday 13 November.
“The suspect said there was a drain blockage outside his property and a worker from Dyno-Rod would be round to fix it.
“Another man, claiming to be from Dyno-Rod, attended a short while later and said he needed £15 to proceed with the works.
“The victim was told he would need to go to Crawley to pay it, which he was not able to do.
“A third man came to take his card so the payment could be processed and left the property.
“The victim received a call a short while later asking for his PIN number.
“The victim quickly realised he had been scammed but, by the time he called his bank, £250 had already been withdrawn from an ATM.
“A similar incident reportedly happened near by on the same day.”
Financial abuse safeguarding officer PC Bernadette Lawrie said: “This impersonator scam is a disgraceful way of defrauding the victims of their cash.
“Please be vigilant about anyone who comes to the door asking for personal or financial information.
“Never give your bank details, transfer money to those you don’t know or trust or give your PIN number or other sensitive information to strangers.
“If you are in doubt about a situation, close the door and call police. If something doesn’t sound right, don’t feel pressured to make a snap decision on matters relating to your finances. Trust your instincts.
“Alternatively, speak with a trusted friend or family member and get their advice on whether you should go through with any action that could impact you financially.”
Sussex Police added: “If you have been a victim of this crime or have any information that could help with our inquiries, please report online or call 101.”
Earlier today a Portslade councillor, Peter Atkinson, warned people to be wary of email and phone scams after fraudsters targeted him twice in a matter of weeks.