Hot water cylinders stolen from Housing New Zealand properties in East Auckland are likely to be sold for scrap metal.

Police say offenders have in the past removed cylinders by smashing the pipes connecting to the house's main water line. Around 500 litres of water is then left to drain out into the house causing extensive water damage.

The Scrap Metal Association of New Zealand represents scrap metal agents around the country and works to combat metal thefts.

President Korina Kirk says copper is typically stolen over steel as it's higher in value. She said copper piping, garden ornaments and planter boxes are also targeted by thieves.

Dealers are required by law to get photo identification of anyone selling scrap metal.

Kirk says the association alerts its members to thefts by sending out information received from police or the public who have reported them on their website.

The reporting network has successfully stopped the sale of many stolen metals, Kirk says.

A Christchurch building company recovered stolen materials valued at $7000 last month after the alleged offender tried to sell it to a metal dealer who recognised the goods and rang the police.

Source: Stuff.co.nz