Danfoss

Swap a stuck, leaking, or unreliable shut-off valve for a modern quarter-turn ball valve -- compression, threaded, and push-fit connections all covered.

Test your water pressure, find the PRV on your main line, and adjust it to a safe 50-60 PSI -- before high pressure wears out your fixtures, appliances, and water heater.

Stop a dripping gate valve stem -- tighten the packing nut, replace the packing, or swap the whole valve for a ball valve, depending on what the situation calls for.

Usually discovered during an emergency -- something is leaking and the valve will not budge. Older gate valves seize after years of disuse. Fix ranges from penetrating oil and patience to full replacement.

Water dripping from around the valve handle or packing nut -- packing failure, not a pipe leak. Fix is usually tightening the nut or replacing the packing, often with the water still on.

Failing PRV lets dangerously high pressure into the house. Bursts supply lines, damages appliances, causes hammer, shortens fixture life, leaks everywhere. Normal is 40-60 PSI. Above 80 is dangerous and needs immediate attention.