Why Steam Boilers Need Regular Maintenance

This boiler was beyond saving after it dry-fired. Hot water was used for re-filling when it cooled down but it had already cracked.

The following article is concentrating on smaller residential steam systems with one LWCO (Low Water Cutoff). A working LWCO will save your boiler. The danger is when boiler maintenance is not done regularly or properly, it will cost you a new boiler and possible flooding damage.

Most homeowners with steam systems know that there is extra maintenance required for their boiler. This is because when the boiler is being used, they should be draining water from it every 7-10 days. Of all the controls that need attention, the LWCO needs the most attention. There are two types:

Float Type and Probe/Electronic Type.

If you are not sure of what type LWCO you have, you can do some further research on the internet. The links below are YouTube videos made by Gordon Schweizer. He is very knowledgeable on steam heat and goes into a lot of detail in his videos.

The LWCO is the control that will prevent the boiler from dry-firing. Without maintaining a minimum safe water level in your boiler, the boiler will crack. This happens because the boiler overheats and becomes an oven. When it gets to oven temperatures, any water that makes contact with the cast iron will crack it. The temperature difference is too great. The metal in the boiler is not capable of handling that temperature.

If you ever come across a working steam boiler without water in the sight glass, don’t just re-fill it. NEVER RE-FILL IT UNTIL THE BOILER COOLS DOWN. This may take hours. The first thing to do is shut off the boiler switch, thereby shutting off the burner/heat source. Since the danger with putting water into an overheated steam boiler is cracking the cast iron, just wait. This may mean getting temporary heaters for the living space.

The reason it is advised that steam boilers are blown-down every 7-10 days is to clean out the sludge and scale build-up from forming. Regardless of whether a LWCO claims to be “self-cleaning”, it should be disassembled, cleaned and tested annually. Refer to manufacturer’s specifications for specific instructions to be performed by an experienced professional. Happy Heating!

M&M #67 Float Type LWCO

Probe Type/Electronic LWCO