Of 40 properties in the $1 million to $3 million price range, the survey found only eight were registered with their local council and had safety compliance certificates.

A further 27 properties had their pools registered with council but no safety compliance certificates; four were neither registered nor had safety compliance certificates. The remaining properties gave an address not listed on the NSW Swimming Pool register.

Although it is possible that some vendors were waiting for non-compliance certificates that aren't available until Friday, the survey suggested many pools are not up to safety standards.

Property experts have predicted a massive logjam of pool inspections for sellers.  The laws, to be introduced on Friday, require that a valid certificate of compliance or non-compliance be attached to the sale or rental contract of any property with a swimming pool or spa.

This is the third attempt at pushing through the changes, which were postponed for a year in 2014 and again last April for a further 12 months.

If the pool is non-compliant, the new owner will have 90 days to bring it up to safety standards.

Julian Peters, special counsel at Aitken Lawyers, said he had drawn up a contract for one client selling after April 29 with a clause saying that a non-compliance certificate was attached but that a compliance certificate would be obtained before completion.

"I think there will be a big logjam of people scrambling to get compliance certificates," he said.

"Some people have been assuming they can sell their property before the 29th and won't have to worry about the pool, and these contracts are now stuck and they are going to have to rethink their position."

Real Estate Institute of NSW president John Cunningham said some agents would keep up with the legislative changes and others who would likely "wing it".

"Properties going to auction on April 30 will only be able to get the certificate [of non-complaince] issued on Friday 29, otherwise they can't go to auction on the Saturday," he said.

"On that day there might be 500 auctions with perhaps 50 of those properties with swimming pools. Are they going to get those certificates issued on that Friday? It's going to have to be a bit of a Houdini act. I think a lot of agents are going to be unaware of that factor."

In the past 13 years, 83 children under five years of age have drowned in backyard pools in NSW and a further 80 children have suffered neurological damage as a result of being immersed in a pool.

The Royal Life Saving Society, using drowning and population data, has compiled a list of the worst areas for backyard pool deaths in NSW. Campbelltown, Camden and Penrith feature on the list. It is also running advertisements about the new regulations on websites and radio stations.

Michael Ilinsky, operations manager at the NSW branch, said that from April 29 buying or selling a property with a spa or pool that didn't have a relevant compliance certificate attached to the contract of sale meant the contract was incomplete and could be rescinded.

He also said if a landlord does not provide a compliance certificate as part of a new lease for a property with a pool, the lease may be invalid.

"Some 55 per cent of all 0- to 5-year-old drowning deaths in a backyard spa or pool happen because of either a faulty gate or a gate being propped open," he said.

"We could halve the drowning figure if pool owners ensured their gates self-closed and self-latched. To achieve this we need to change human behaviour."

Local Government Minister Paul Toole said the NSW government was committed to creating an effective pool barrier framework that protects the safety of children around backyard swimming pools.

"While nothing can substitute for responsible adult supervision around a swimming pool, a compliant barrier helps minimise the risk of drowning or near drowning," he said.

"These new regulations will highlight safety requirements and responsibilities when buyers take possession of a property with a pool."