Plumbing expert witness for defense opines on commercial building flood caused by alleged plumbing defect

A plumbing expert witness for the defense opines on a case happened in Alaska involving a hydrology engineering company that was contracted with a large-scale building developer to provide mechanical and plumbing drawings. Six years after the building’s completion, in the roof-top mechanical room, the relief valve on the backflow preventer room connected to the cooling tower makeup water line allowed water to be discharged from the relief valve and into the air gap fitting. Some of the water went down the drain, some went down the stairway and some flowed down through a duct-work penetration into the electrical rooms three floors below. This caused some arcing in the electrical room which caused a wet pipe sprinkler head in that room to discharge. The water from the sprinkler head caused the majority of damage.

The building owner alleged the engineering company should have known that the back-flow prevention system would be located in a low-visibility area, contrary to installation instructions and that the floor drain should have been larger to accommodate overflow. It asserted a claim for negligence and sought nearly $1 million in damages.

Question(s) For Expert Witness

1. Did the designer of the back-flow prevention system meet the standard of care for a reasonably prudent plumbing engineer?

2. Was the location in the rooftop mechanical room appropriate for the application?

3. Was the capacity of the floor sink in the mechanical room adequate for the manufacturer's published catastrophic or worst-case relief valve discharge rate?

Expert Witness Response

After reviewing the documents, photographs and drawings provided, the I offer the following opinions:

• The plumbing designer fully met the standard of care in this design for a reasonably prudent plumbing designer. The design met all applicable codes and standards and is consistent with designs in similar buildings.

• The backflow preventer was placed in a mechanical room that was specifically constructed to house mechanical equipment. The design engineer conformed to the information provided by the manufacturer. The installing contractor stated the device was installed in accordance with the manufacturer's recommendations and/or the municipality’s Uniform Plumbing Code. Other BFPs in similar installations in this building have been stated as meeting the same requirements by multiple other testing agencies, the drawings were reviewed and approved by the city and the installation was inspected by city inspectors.

• The floor sink in the mechanical room was sized adequately for the outlet size on the manufacturer's provided air gap fitting and was the size recommended by the manufacturer. The pressure at the BFP from the upfeed domestic water system allows the drain and piping system to be of adequate size.