Water hammering is a loud banging or knocking sound in pipes that happens when flowing water stops suddenly, creating a shock wave through the plumbing. This pressure spike can damage pipes, joints, and fixtures over time. Common causes include fast-closing valves, high water pressure, or long pipe runs without proper cushioning. Plumbers often install water hammer arrestors to absorb the shock, reducing noise and stress on the system.

Pressure reducing valves (PRVs) control incoming water pressure from the municipal supply. City water pressure can be much higher than what home plumbing can safely handle—sometimes over 100 psi. A PRV lowers it to a safer level (typically around 50–60 psi) to prevent leaks, extend fixture life, and improve comfort. These valves can wear out, leading to fluctuating pressure or water hammer, and may need adjustment or replacement by a professional.

Expansion tanks protect against excess pressure caused by thermal expansion in closed water heating systems. When water is heated, it expands, and without a place to go, pressure can spike—damaging pipes, valves, and appliances. An expansion tank has an air-filled bladder that absorbs the increased volume, maintaining steady pressure. A failing expansion tank may become waterlogged, causing pressure issues and triggering the relief valve.

Together, these components—arrestors, PRVs, and expansion tanks—keep water pressure stable, prevent noise, and protect your plumbing system from stress and premature failure.