Leaks at the spray valve usually come from loose screws or fittings, worn internal parts or scale. EPA suggests tightening screws and fittings when possible, and replacing the valve if it can't be adjusted to perform properly. Replacements must meet the federal flow limits for their spray-force class.
Why do they leak?
EPA's WaterSense at Work guidance says pre-rinse spray valves should be periodically inspected for leaks and for broken or loose parts, and that kitchen staff should be trained to report leaks. It also says to inspect for scale buildup, which restricts flow, and advises against boring holes in the valve, because that can raise water use or cause performance problems.
In practice, the leak shows up in one of three places: the valve body or lever, the connection to the hose, or the mounting at the faucet. EPA's field study that led to its specification identified leaking and malfunctioning products as a concern, which is why its performance testing included a life-cycle test. A weeping valve is a known wear item.
Tighten or replace?
EPA's guidance: if necessary and possible, tighten screws and fittings to stop leakage. If the product cannot be manually adjusted to perform properly, consider replacing it. EPA also notes that these valves are relatively inexpensive, so replacement is generally preferable to extensive repair, and that flow-control inserts added to old valves can backfire by lengthening rinse time.
If scale cannot be removed, replacement is the answer again.
What must a replacement meet?
Since 2019, federal regulation requires every commercial pre-rinse spray valve sold in the United States to meet a maximum flow rate by spray-force class: 1.00 gpm for Class 1 (5.0 ounces-force or less), 1.20 gpm for Class 2 (over 5.0 up to 8.0) and 1.28 gpm for Class 3 (over 8.0). EPA's guidance says to choose a compliant model with a flow rate of 1.28 gpm or less and a spray force suited to the end use. Choosing a valve goes through that decision.
EPA says pre-rinse spray valves can account for nearly one-third of the water used in a typical commercial kitchen, so a leak at the dish station is not a small one.
Is it a plumber's job?
Swapping a sprayer is a quick job, but the stop valves, hose connection and faucet it mounts to are plumbing. If the leak is at the mounting or under the sink, diagnose the cabinet first.