credit:keith williamson(Flickr)

Doctors have warned that pool skimmer boxes without a cover can be fatal to children.

The devices draw in water from the pool's surface, to gather up leaves and other floating debris, and children can be seriously injured if they inadvertently block this powerful suction process.

Three cases are listed in the latest Medical Journal of Australia, all children under six years who briefly sat on an unprotected skimmer box where they became quickly, and potentially lethally, stuck.

Professor Danny Cass, lead author on the study and a trauma surgeon at the Children Hospital at Westmead in his statement said that children may suffer catastrophic injuries if they sit on the pool skimmer box which looks similar to a potty. Due to the suction, children who got stuck may suffer complex internal injuries to the intestines and bowel. The injuries suffer may prove to be life -long, if not fatal.

One young boy suffered an external rupture of more than a metre of his intestines while all three cases required complex restorative surgery.

Prof Cass said voluntary standards for pool drains were introduced in 1980, and updated in 2003, but it appeared this had not totally removed the risk.

In two of the cases, the child was injured after the skimmer box protective cover had been temporarily removed.

Authorities should consider the need for a kill switch that would shut off the skimmer box if its cover was not in place or it became blocked, he said.

The cases were rare but the injuries were terrible, Prof Cass said.

Most parents watch their children as they play in the backyard pool ensuring they don't drown, however, few know the risks posed by the skimmer box, he said.

Many pools now have a lid over the top of the skimmer box, but with older pools they do not, and parents must remain vigilant and warn their children of the risks.