Expansion Tanks

Expansion tanks for water heaters control thermal expansion in closed plumbing systems, protecting pipes, fixtures, and the heater from damaging pressure spikes. By absorbing expanding hot water, a properly sized thermal expansion tank helps prevent nuisance dripping at the temperature and pressure (T&P) relief valve, reduces stress on joints and seals, and supports longer equipment life and plumbing code compliance wherever a pressure-reducing valve or backflow preventer is present.

Choose a potable water expansion tank sized for your heater capacity, incoming static pressure, and temperature setpoint. Look for NSF/ANSI 61 certification, a heavy-duty steel shell, a butyl or EPDM diaphragm or bladder, a corrosion-resistant threaded connection, and a factory pre-charge that can be adjusted through a standard Schrader valve. Typical models are rated to 150 psi and 200°F; verify ratings against your system. Many tanks can be mounted vertically or horizontally; use a bracket or strap to support the weight of a water-filled tank.

Installation is straightforward for pros and confident DIYers. Install the expansion tank on the cold-water supply line to the water heater, downstream of any PRV or backflow device. Set the air pre-charge to match your home’s static water pressure using an accurate gauge. Use a tee and ball valve for isolation, apply approved thread sealant, and check for leaks. Signs your tank needs service include frequent T&P valve discharge, fluctuating pressure, or a waterlogged tank that feels heavy with no air cushion.

Find options here from compact 2-gallon units to larger capacities for high-demand homes and light commercial use, along with mounting straps, valves, and pressure gauges. Adding the right water heater expansion tank improves system stability, reduces maintenance, and supports safer, quieter operation across your plumbing system. Browse sizes, specs, and installation kits to match your water heater, municipal supply, or well system precisely today.