Why Does my Steam Boiler Run Out of Water?

Automatic Water Feeder for Steam Boiler

All steam boilers need a constant supply of water from a make-up water source. In a steam boiler system there are steam vents that vent condensation produced by the steam. The steam vents can be found on the radiators and throughout the steam pipe system especially on large steam systems that serve larger buildings. Venting is limited to a small amount of the entire water and steam volume inside the steam piping and radiators but does need to be replaced. Most of the steam condenses and is returned to the boiler through the return piping system either by gravity or a steam condensate pump. As the system uses steam it vents the condensation or steam and this displaces water from the steam system that needs to be replaced and the replacement water comes from a make-up water source.

Steam Boiler Make Up Water

Steam Vent on a steam radiator

The make-up water source usually comes from the city supplied water source and is controlled by an automatic water feeder that is directly controlled by a low water cut-off control located on the boiler. The low water cut-off has a float inside of it that measures the level of the water inside the boiler. At a specific level the float activates a switch that sends power to the automatic water feeder that feeds water to the steam boiler system when the level inside the boiler drop below a critical level. This refreshes the water and fills the boiler to safe levels. There are some maintenance requirements on most steam boilers for the low water cut-off and if proper maintenance is not done as required by the manufacturer the system can foul and prevent proper functioning and even a dangerous condition of the steam boiler system.

Low Water Cut-Off Maintenance for Steam Boilers

Low Water Cut-offs on steam boilers typically have a lever on the cut-off itself. On a regular schedule the lever should be turned and the water from the steam boiler purged. The purging is referred to as a blow down of the steam system. What will come out of the steam system is dirty water. The system should be purged until the water becomes clear.

If this has not been done on a regular schedule the boiler system can become fouled with much. The much will foul up the controls and eventually will not function properly and lead to failure of the system especially the low water cut-off and the other controls in the steam boiler system.

Flushing The Steam Boiler with the blow down valve on the low water cut-off