Expansion tank installation in Aurora, CO

A 50 gallon water heater can expand by more than half a gallon when it heats from cold to its set temperature. In an open system, that water simply pushes back into the city main. Once a check valve or pressure reducing valve blocks that path, the extra volume has to compress somewhere, and pressure in the house climbs fast.

An expansion tank is a small steel vessel with an air chamber and a rubber bladder or diaphragm inside. As water expands, it pushes into the tank against the air cushion, which compresses and keeps house pressure close to normal. When you open a hot tap, the air pushes that water back out into the system.

Expansion tanks come in a few sizes, and the right one depends on the water heater's capacity and your incoming water pressure. Higher house pressure needs a larger tank, because the air cushion starts out more compressed. Most homes with a 40 or 50 gallon heater use a two gallon tank, while larger heaters or higher pressure call for something bigger.

Pre-charge matters as much as size. Tanks ship from the factory at a standard air pressure, and that setting needs to match your house water pressure before the tank is installed. A tank charged too low fills with water and does nothing. We measure your static pressure, set the air charge with a gauge, then mount the tank.

The tank installs on the cold water supply line feeding the water heater, between the heater and the shutoff valve. A full expansion tank is heavier than it looks, so it needs support rather than hanging from a thin copper line. We use a bracket or strap to the wall or framing so the weight never stresses the pipe.

Orientation is flexible on most models, but we avoid spots where a future leak would damage finished drywall or flooring. If your heater sits in a tight closet, we plan the tank position so it does not block the gas valve, the drain valve or the relief valve discharge line you may need to reach later.