Enormous clusters of wet wipes are creating "fatbergs" that are clogging up sewer pipes across NSW, including a one-tonne cluster that blew out a pumping station near Lake Macquarie.

Three-quarters of the one-tonne cluster of sewage and wet wipes was removed with specialised equipment from the station at Eleebana.

But the rest, 300 kilograms, was removed by hand, one bucket at a time, according to Hunter Water Corporation spokesman Nick Kaiser.

"Wet wipes are responsible for around 80 per cent of all sewer blockages in Hunter Water's system," Mr Kaiser said.

"These can cost thousands of dollars to repair and if they occur in people's private plumbing that cost is worn by the customer."

It is a problem worldwide with wet wipes advertised as flushable taking years to break down and sometimes mixing with fats and oils to form "fatbergs".

"Only human waste and toilet paper should ever be flushed down the toilet," Mr Kaiser said.

A survey of consumers in the Illawarra region found one in four Illawarra residents flushed wet wipes down the toilet, which can clog up pipes and block toilets. One resident said he had been hit with a $16,000 plumbing bill.

The Water Services Association of Australia estimated wet wipes are costing water utilities $15 million per year.

According to a Sydney Water spokesman, wet wipes are clogging up the sewerage systems in the Illawarra on a "constant basis", requiring regular removal.

Across the network, the wipes can combine with items like fats and oils to create "fatbergs" – which lead to environmental damage when the blockages create sewage overflows into creeks, rivers and beaches.

When people read "flushable" they believe that means the product will break down, but the spokesman said this wasn't the case.

"The issue is certainly that wet wipes don't break down like toilet paper," he said.

"Toilet paper breaks down almost immediately when flushed. Independent tests undertaken by Choice showed that the wet wipes hadn't broken down in any way during a 21-hour testing period."

Last year Choice gave Kleenex a Shonky Award for its flushable wipes.

Each year, Sydney Water removes 500 tonnes of wipes from the network across the Illawarra, Blue Mountains and Sydney every year at a cost of $8 million per year.

"Many customers have told us that based on the flushable labelling of wipes they thought it was OK to flush, only to be hit with expensive plumbing bills," Sydney Water's service delivery general manager Eric de Rooy said.

Sydney Water recommended ignoring the "flushable" claim on the packaging.

"Our message to customers is simple," Mr de Rooy said.

"Keep wipes out of pipes – bin it, don't flush it."