The 20 gallon WXTP Thermal Expansion Tank is utilized on potable water lines between the backflow preventer or pressure reducing valve and the water heater for protection against water thermal expansion in commercial applications. As the system pressure increases, water enters the tank, expanding into a pre-charged air chamber to keep the system pressure below the relief valve setting. Materials for the WXTP include a steel shell with an epoxy finished coating, corrosion-resistant stainless steel connection, and an FDA approved Butyl rubber bladder to prevent water contact with the shell. Other features include free standing base-mounted tanks, and an adjustable pre-charge of 40 psi.