Boiler Tanks

Boiler Storage Tanks

  • Raypak Boiler Storage Tanks – required in conjunction with WH water heaters. We commonly sell both the Non-ASME stainless steel 110 gallon storage tank, which has a 150 PSI maximum working pressure and 180 degree maximum temperature, and the ASME 115 gallon or 175 gallon storage tanks, which have two magnesium anodes included and are insulated and jacketed.

  • ASME vs Non-ASME – if the total system volume does not exceed 120 gallons, a non-ASME tank may be used. Otherwise, an ASME tank is appropriate.
  • Glass Lined Storage Tanks – standard capacities are up to 1,000 gallons and are factory jacketed and insulated.
  • Jacketed Storage Tanks – capacities from 140 to 2,500 gallons in horizontal or vertical mounting.
  • Typical Storage Tank Piping – unions and isolation valves for future maintenance are often overlooked by contractors trying to save money short-term.

Buffer Tanks

  • Buffer tanks come in a variety of sizes, horizontal or vertical, and are used with high recovery low-mass boilers that need certain minimum water volumes to avoid temperature change issues. Common sizes are 40 gallon, 60 gallon, 80 gallon, and 115 gallon depending upon the system size.

Expansion Tanks

  • Expansion tanks are used to accept expanded fluid in a closed-loop hydronic system (applicable to comfort heating systems or also called a hydronic loop) to control pressure buildup, improve comfort and help reduce energy costs. When water is heated, it expands, thereby increasing pressure in a closed-loop system. The most common design of a boiler expansion tank is an internal bladder or diaphragm that allows for expansion up to a certain gallon capacity and pressure setting. Sizing the expansion tank appropriately for your system is a critical step, often overlooked.There are in-line models of expansion tanks that are piped directly on the system or there are vertical floor-standing expansion tanks available for larger sizes.
  • The expansion tank should always be tied into the system on the suction side of the system pump, never on the discharge side of the pump. This is also called the point of no pressure change in the system.
  • Air vents are also used in hydronic systems along with the expansion tank to release excess air in the system. In larger systems, having an air separator installed may also be necessary.

Boiler Feedwater Tanks

  • Steam boiler systems always use a feedwater tank and boiler feedwater pumps to maintain an appropriate level of water in the boiler. Feedwater tanks vary in capacity by the size and demand of the entire system, typically in the range of 30 gallons up to 1,000 gallon tanks.
  • Sizing a boiler feedwater tank needs to take into consideration the facility water supply, any condensate return line (if available) and the capacity, as well as boiler and system demand that will drain the available water.
  • Larger feedwater tanks require periodic cleaning, inspection, or potentially Ultrasonic Thickness (UT) testing or other NDT method on the tank and welds to check for corrosion levels.
  • We typically like to see a redundant boiler feedwater pump on the system, because too often we see a manufacturing plant production shutdown or safety issues of boiler low water over a boiler feedwater pump.
  • Proper treating and heating of boiler feed water will optimize the lifetime of your boiler. Improperly heated feed water leads to lower boiler efficiency and system failure. Preheating feed water for ideal hot water temperature will allow the boiler to have high efficiency rates and minimize the required chemical treatment and reduce thermal shock on the boiler.
  • To produce high quality steam to transport throughout your entire facility, a boiler water treatment plan is imperative. It focuses on removing chemicals that contribute to equipment corrosion and control the quality of the feedwater. Water quality is important for proper and safe operations.

Condensate Tanks & Condensate Receivers

  • A condensate tank, also known as condensate receivers, captures valuable condensation usually discarded as the boiler heats water and sends it back to the boiler room to be reused. It is a valuable part of an HVAC system as it maximizes efficiency.
  • Capturing and reusing condensation is beneficial for the boiler system. It allows the water temperature to remain more consistent, less water is necessary for the functioning of the boiler system, and it prevents damage and corrosion to the system. Also, the condensate is pure so that it will require less blow down.


  • How do I know if an expansion tank is working properly or not?
    • Watch the boiler pressure gauge as the system heats up. If the pressure rises noticeably then the tank is (a) undersized (b) waterlogged (compression tank) (c) ruptured bladder (bladder/diaphragm tank) (d) not adequately pre-charged (bladder/diaphragm) or (e) Valve is closed isolating expansion tank from the system.