Photo Gallery B2: Galvanized Steel to Brass Failures

The direct connection of galvanized steel pipe to a brass valve is a near absolute guarantee of an advanced thread leak or failure.  This is due to the more aggressive attack of brass against the zinc protective finish of galvanized steel pipe.  Connecting copper to galvanized steel, which is less common but such as might exist at a domestic water system as it trims out, produces a similar result.  The deterioration is very localized at the already weakened cut threads.

Such events are far more common for open condenser water systems due to their generally higher corrosion activity.  The issue is less common for closed chilled or hot water systems, although the threat is always present.  For heated systems, such as domestic hot water, the impact is even further amplified since higher temperatures accelerate the corrosion process.  For cities like Chicago where galvanized steel pipe was inappropriately installed for domestic hot water service throughout the city, the installation of brass shut-off valves only add to the problem.

The vulnerability of galvanized steel pipe to this form of corrosion, generally unknown to the industry, is directly related to its time in service; a curious contradiction present due to continually declining quality and corrosion resistance of the galvanized steel pipe itself.  Going back in time, the quality of galvanized steel pipe was far superior; reducing the impact of galvanic attack although with the inevitable losses caused by many decades of use.  Given the far lower quality of today’s galvanized steel pipe, thread failures due to galvanic activity from a brass valve have been documented within 5 years or less.