Thermal Expansion Tanks

A thermal expansion tank or expansion vessel is a small tank used to protect closed (not open to atmospheric pressure) water heating systems and domestic hot water systems from excessive pressure.  The tank is partially filled with air, whose compressibility cushions shock caused by water hammer and absorbs excess water pressure caused by thermal expansion.


Thermal Expansion Tank Services


GPS Plumbing, a full service plumbing company, provides a complete line of professional thermal expansion tank:


  • Installation
  • Repair
  • Replacement


services for most if not all types, styles, sizes, and brands.  We also provide a full set of water pressure management solutions, with both offered at reasonable, equitable, and affordable prices.


We correct and fix irritating and potentially dangerous condition such as:


  • The buildup of unusually high pressure in a water supply system - even when a pressure reducing valve is installed
  • Pressure surges
  • Chronic or continuous dripping of a temperature and pressure (T&P) relief valve
  • Dripping faucets
  • Leaking toilet tank ball cock fill valves
  • Other water pressure related conditions


If expansive or high water pressure conditions exist in your home, we can:


  • Quickly diagnose the problem
  • Provide a cost effective solution
  • Offer a free no obligation solution quote


The sooner the better when it comes to fixing an expansive water problem.  Fixing the problem as soon as possible minimizes any potential damage to your water heater and water supply system.


More About Thermal Expansion Tanks


Thermal Expansion Tanks - How They Work


The expansion tank relieves the pressure that builds up through thermal expansion in a closed-system by giving the excess water somewhere to go.  As the water pressure increases, it pushes the diaphragm of the expansion tank down, compressing the air on the other side, creating more space for the influx of water, and relieving the building pressure of the system.


Thermal Expansion Tank - Tank Design


A rubber diaphragm divides the tank into two sections. 


  • One side connects to the piping of the heating system and therefore contains water
  • The other, the dry side, contains air under pressure, and normally a Schrader valve (car-tire type valve stem) for checking pressures and adding air


When the heating system is empty or at the low end of the normal range of working pressure, the diaphragm pushes against the water inlet; as the water pressure increases, the diaphragm moves, compressing the air on its other side.


When to install a Thermal Expansion Tanks


The installation of a thermal expansion tank is recommended/required when any of the following occurs:


  • When a conventional water heater is replaced
  • When a backflow device is installed in water service line
  • During a water meter replacement
  • During new home construction
  • When a pressure reducing valve is installed on the water service line
  • When PRV is replaced on the water heater
  • Anytime thermal expansion of water creates an unsafe home condition


When to Contact GPS Plumbing


Thermal expansion of water in home’s water supply system can create several irritating and potentially dangerous conditions including:


  • Pressure surges
  • Chronic or continuous dripping of a temperature and pressure (T&P) relief valve
  • Dripping faucets
  • Leaking toilet tank ball cock fill valves


When you notice, any of these conditions call GPS Plumbing.