Electric pool cover owner Warren Cairns demonstrates how sturdy they are in this file photo.

Pool builders and designers have slammed a government ruling banning the use of automatic pool covers instead of fences.

NZ Pool Industry Association executive Geoff Bonham said the Ministry of Business, Innovation and Employment made the "wrong" decision on automated pool covers.

He believed the determination should have been challenged by the Marlborough District Council, the territorial authority that sought clarity over the use of covers instead of fences.

SUPPLIED The Ministry of Business, Innovation and Employment has ruled that swimming pools must have a fence around them.

The ministry's ruling last month ended the use of waivers, or modifications, of the Building Act to allow pool owners to have automated pool covers instead of fences as a barrier.

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"I think [the ministry] has got it wrong, really," Bonham said.

Last month, the ministry said it did not view pool covers as a safe option compared to the "risk associated with a compliant pool fence", which had automatically closing gates or door alarms.

Bonham said the Building Act did not explicitly rule-out using automatic pool covers instead of fences.

"There is no mention in the [Building] Act that the pool has to be fenced, it says a barrier can be used, an auto pool cover is a barrier.

SUPPLIED Pool architect Peter Townsend says the Government ruling on automated covers is "unfortunate".

"I think each property has to be looked at and the council makes up its [own] mind that a cover is suitable and [whether] there is no adverse effects for children," Bonham said.

Bonham challenged the ministry's claim that "the essential difference" with a pool cover was that adults would have to take "active steps" to keep the pool cover shut, unlike self-closing gates.

But self-closing gates could still be left open if people wanted to, Bonham said.

SUPPLIED NZ Pool Industry Association executive Geoff Bonham with a swimming pool cover in Auckland.

"An adult can leave the pool area and leave the gate open so what is the difference if they have an auto pool cover?

"A child cannot open a cover as the [keypad] is 1.5-metres off the ground and ... if the child does not know the code they cannot open the cover," Bonham said.

Blenheim pool builder Mike Freeth said last month that a common theme in pool inspections was faulty gates.

"I was at a school a couple of weeks ago, and the gate by the school pool was malfunctioning, the latch was broken off by someone and the gate wasn't self-closing," Freeth said.

Auckland-based swimming pool architect Peter Townsend labelled the determination "unfortunate".

He praised the Marlborough District Council for "correctly" pointing out two reasons that showed the safety of automated covers, since waivers were first used in Marlborough in 1999.

"[They pointed out] during that time no children have drowned where they are installed.

"The council also correctly points out that while the pool cover is open the pool is in use and therefore children are under supervision," Townsend said.

The purpose of the legislation, which was "to prevent drowning of, and injury to, young children" under the age of 5 by "restricting unsupervised access to residential pools" was achieved by an automated cover, he said.

"Both common sense and the service history of approved pool covers in the Marlborough region during the past 19 years confirm they are an effective means of preventing unsupervised access to pools," Townsend said.

NZ Pool Industry Association chief executive Larry Ogden opposed the ruling, but understood some of the reasoning behind the decision.

"The major issue MBIE mentions in my interpretation is the pool owner forgetting to close the cover, thus eliminating the barrier.

"Although this does not appear to be an issue in the years these covers have been used as the sole barrier, there remains the potential of a tragic event in the event of a single act of forgetfulness," Ogden said.

But "many pool drownings" were linked to "faulty" or "inoperable" gates, he said.

"So even these are not a 100 per cent safety feature," Ogden said.