Why Is My Condensate Tank Overflowing?

Common Causes

• Failed-open steam traps: Live steam blowing through traps enters the condensate return system, pressurising it and preventing condensate from draining. The excess volume overwhelms the tank.
• Condensate pump failure: If the pump that transfers condensate from the receiver to the boiler feedwater tank fails, condensate accumulates and overflows.
• Blocked return lines: Scale, dirt, or pipe corrosion can block condensate return lines, causing condensate to back up into the receiver tank.
• Level control failure: The float switch or level controller that starts and stops the condensate pump may be stuck or failed.
• Excess condensate generation: A process change or equipment malfunction may be generating more condensate than the system was designed to handle.
• Flash steam expansion: High-pressure condensate entering the tank flashes into steam, occupying much more volume than liquid water and causing apparent overflow.

Diagnosis Steps

1. Check the condensate pump. Is it running? Is it cavitating or making unusual noises?
2. Check the level controller. Is the float free to move? Is the switch functional?
3. Check for steam at the tank vent. Continuous steam indicates failed-open traps in the system.
4. Check return line temperatures. A cold section may indicate a blockage.
5. Survey steam traps. Identify and replace any failed-open traps.
6. Check for process changes. Has a new heat exchanger or process been added without upgrading the return system?

Solutions

• Fix failed traps: Survey and replace all failed-open steam traps. This is the most common cause of condensate tank overflow.
• Upgrade pump capacity: If the pump is undersized for the current condensate load, install a larger pump or add a second pump.
• Install a high-level alarm: Add a level sensor that triggers an alarm before the tank overflows, giving operators time to respond.
• Clear blocked lines: Inspect and clean return lines, especially at elbows and low points where debris accumulates.
• Install a flash vessel: If flash steam is causing the overflow, install a flash vessel upstream to separate steam from condensate before it enters the tank.