Tap fault or Fitting Fault?

[Grahamharris]

We have recently undertaken a house refurbishment but following the new bathroom being fitted we experienced a severe leak which has caused significant damage to the ceiling, the recently plastered walls downstairs and the newly laid wooden flooring. Our contractor is saying the tap must have been faulty and is denying any liability. The tap that we bought was a wall mounted tap with the following spec.

• Made from solid brass with hand polished chrome finish
• Durable ceramic disc cartridge prevents any leaks
• Includes flexible tap connectors
• Suitable for most UK household water system
• Require minimum 0.5 bar water pressure, 1 bar or higher for best performance
• If you have a gravity fed system(tank in the loft), a water pump is required for optimal water pressure

The contractor is claiming that the washer inside the tap must have been damaged. Do any experts have an opinion on this?