It's that unwanted single mattress the kids have grown out of, the old TV it took 10 years to throw out, or the finally broken vacuum cleaner that never really worked anyway.

No longer wanted, or needed, common household items like these often end up on the footpath, down back alleyways or even in the bush.

Since 2004, NSW local government areas have reported an increase in illegal dumping, a problem costing one in 10 NSW councils more than $500,000 a year.

Exactly how much it is increasing is "the difficult question," said Steve Beaman, director of the Environment Protection Authority's waste and resource recovery branch.

"Dumping by its very nature is secretive - people go out of their way not to get caught. So one of the things we've introduced is a new statewide database with public land managers, to use smartphone technology to report dumping and help us develop a comprehensive database."

According to the EPA's latest report on illegal dumping, the majority of councils across NSW define illegal dumping as a "major or moderate problem".

More frustrating, said Mr Beaman, is that more than 10 per cent of the community had deliberately travelled to covertly dump illegal waste elsewhere in the past year.

"We're losing good resources that can be recovered; glass, timber, paper and cardboard. Even old mattresses, they can be used to make sporting equipment like boxing bags," Mr Beaman said.

The EPA found that of the 1000 people it surveyed, one in three had illegally dumped waste over the past year, mainly on the kerbside.

Its report found that people who were aware of legal disposal methods were no less likely to dump illegally.

The top items to be dumped illegally are household furniture, clothes and mattresses (20 per cent), household domestic rubbish (17 per cent), green waste (17per cent) and household whitegoods (10per cent).

"People often think green or garden waste can be put back out in the bush, but you are increasing bushfire hazard and potentially spreading weed seeds into the bush which can be very damaging," Mr Beaman said.

Darryl Nichols first noticed an increase in illegal dumping in 2010. Feeling that something had to be done, he launched Garage Sale Trail to encourage people not to "dump it, sell it.

"Five years on, what started as a grassroots initiative on Bondi Beach has now become a nationwide event, asking households across Australia to host their own garage sale on October 24," he said.

"The idea back then was to create awareness," Mr Nichols said of the event, which was recently announced as a finalist in the community category for this year's Premier's Sustainability Awards .

"We have a lot of stuff in our attics and garages, most of which is going to end up in landfill. The premise is that passing on what you don't want to someone who does want it is a great method of sustainability."

Mr Nichols said the day also means unused goods are picked up from one home and taken to another, relieving some strain on charities.

Across NSW it's estimated that 40 per cent of donations to charities are unusable, with illegally dumped waste burdening charities with $3 million in disposal costs each year.

Zero-waste advocate Tim Silverwood said when it comes to waste, the community needs to be on the front foot.

"We choose dumping or the bin because it's the easiest option, but we need to recognise that any waste going to landfill is unacceptable ... one business's waste [can be] another's feedstock."

Mattresses: According to Mission Australia Mattress Recycling, mattresses are the most common items put out for council clean-ups. There are specified mattress recycling facilities across Australia that reuse materials to make carpet underlay, boxing bags, kindling, mulch and animal bedding.

Whitegoods: Most local councils hold whitegood clean-up days, with some charging a fee for the service. Whitegoods are also accepted for disposal at some local waste depots. Some residents in NSW are eligible to have their second fridge collected and recycled as part of the Fridge buyback scheme. For those who meet the eligibility criteria, the scheme provides free collection, and a $15 rebate, when there are no more than 6 steps involved.

Old tyres: Some landfill sites or tyre outlets accept old tyres for recycling. Old tyres can be recycled to make asphalt, footwear and cushioning material used on playgrounds.

Medicines: Every medication has a use-by date, and if kept beyond that date they can become a household hazard. Out-of-date and unwanted medicines can be returned to any Australian pharmacy for free and safe disposal.

Light bulbs: Valuable resources can be recovered from light bulbs. They can be dropped off at selected neighbourhood service centres and some local libraries.

Motor oil: Old oil should be disposed of correctly after you change the oil in your car, lawnmower, boat or chainsaw. Some chemical cleanouts held by local councils or the state government collect used motor oil. It can also be disposed of at selected transfer stations, waste management centres or landfill sites.

Paint and household materials: These can be disposed free of at Household Chemical CleanOut events held in various locations across NSW. Any liquid left in old paint tins should be tipped onto an absorbent material, like a newspaper, and disposed of with general waste once it's dry.

X-rays: These can be recycled and processed to extract silver.

Thermometers: Old mercury thermometers can be disposed of at household chemical cleanout for free.

With Caitlin Wheeler