Christchurch Hospital will consider installing advanced tap filters if a cluster of lung infections returns to its Intensive Care Unit.

Last month two patients contracted infections from Stenotrophomona bacteria, which is often water-borne.

The hospital suspects tap water was the source.

Microbiology Director, Dr Josh Freeman, said they've managed to use sterile and boiled water since to avoid further infections.

He said they could also put bacterial filters on the taps, but that would cost up to $100,000 a year to maintain.

"That sort of money could be invested elsewhere and have far greater benefits."