Common causes are age and corrosion, overtightening during install or repair, reusing parts that should be replaced, and stops that are never operated. Manufacturers say to inspect stops annually and replace them if damaged or corroded. A failed one leaks into walls and cabinets, so replacement beats repeated tightening.
Why do they fail?
Age and corrosion. BrassCraft's instructions for its supply stops say to inspect them annually and to replace them if damaged, deteriorated or corroded, and warn that failure to do so may result in product failure and property damage.
Overtightening. The same instructions state that overtightening can cause the product to crack and fail over time. A stop that drips at the nut is often fixed once, then cracked by a second quarter turn.
Reuse. The instructions say not to reuse the product.
Wrong connector for the stop. BrassCraft warns that a connector must match the water supply connection, and that using the wrong one may cause leaks. The stops are also not meant for use with connectors that have a solid brass cone termination point.
Never being turned. A valve that is never operated can seize or stop sealing. NIBCO recommends exercising ball valves from fully open to fully closed periodically, such as at least once every 6 months. Many restroom stops go years without it. A stop that won't shut off completely is the result.
What is the fix?
Replace the stop or supply line rather than adding more tightening. Quarter-turn ball stops are common today; BrassCraft's quarter-turn stop is rated for temperatures from 40 to 160 degrees Fahrenheit and pressure up to 125 psi for its press-connect version, and is IAPMO-certified to ASME A112.18.1/CSA B125.1. Check the rating of whatever stop is chosen against the building's pressure.
Replacement means the water to that fixture or restroom has to be off. Plan the shutdown so restrooms stay available, and see temporary restroom planning if more than one is out. For the toilet side, replacing a supply line shows the steps.
What should a property manager do?
Add stops and supply lines to the restroom checklist, so they are looked at before they fail. A preventive plan is the natural home for that, and fixture replacements are a good time to replace the stops too.