Summary
Corroded shutoff valve at main riser replaced. Customer reported intermittent water at second-floor fixtures. Found quarter-turn shutoff at main riser seized and corroded at the joint. Isolated supply, replaced valve and adjacent nipple, cleaned mating surfaces. Pressure tested at 80 PSI, held 15 minutes. No leaks at joint. Water restored to all fixtures and verified at second-floor bath.
Photos · Before & during