However, the quick thinking of a Porirua scrap metal dealer shows that thieves are not likely to be able to make an easy dollar out of the theft of drain covers.
Local scrap dealer Ingot Metals has recovered seven cast-iron drain covers from people who have turned up and attempted to sell them as scrap metal.
Porirua City Council reports that the scrap dealer has passed on the would-be seller's details and other information to the Police.
Porirua City Council Roading Manager Geoff Marshall says: "It is great to see responsible scrap dealers working with councils to keep the community safe by not purchasing sump tops and reporting approaches to Police."
In Wellington, the City Council is urging residents and motorists to keep an eye out for suspicious activity around the suburbs to help prevent the theft of more of the cast-iron covers.
The Council's Infrastructure Director, Stavros Michael, says the covers have been stolen from streets in Island Bay, Brooklyn and the Seatoun Bays. "They leave holes into which a small child could easily fall and drown - or cause death or serious injury for any cyclist who has the misfortune to ride into one of the open sumps.
"If a car drops a wheel into one of the open sumps then the damage could be severe."
Mr Michael says Police have been notified to the spate of thefts. "We think this is a sign that the global scourge of metal theft is starting to take root in New Zealand."
He says the global recession appears to have coincided with high prices for scrap metal. "People think they'll make easy money out of thieving things like drain covers. But we urge would-be thieves to think twice before getting involved - the returns are paltry compared to the possible punishment."
Hutt City Council says the theft of sump grates appears to have declined just for now - largely due to a combined effort by Police, the Council, the NZ Scrap Metal Association and residents. However City Council Road and Traffic Contracts Supervisor Colin Lunn says: "We need to remain vigilant and ask people to keep us informed of any missing sump grates or to contact the Police direct if they note any suspicious activity out on the street."
In Wellington, Mr Michael asks residents to call the City Council on 499 4444 as soon as possible if they notice a drain cover missing - or call the Police if they see people acting suspiciously around drains. "If someone's lugging drain covers around in a Wellington street and they don't appear to have a vehicle bearing City Council, Capacity, Transfield or Downer logos, then they're probably not legit. Try to get their rego at least."
Police are also urging residents to call the 0800 555 111 Crimestoppers number if they have information on these thefts.
Where thefts have occurred, new grates are being installed as soon as possible - or temporary covers are being put in place.