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Residential Steam Boiler Maintenance

Monthly Maintenance on Steam Boilers

Every month during the heating season you need to drain water from the system. How much? I like using a 5 gallon bucket. There are two primary reasons for doing this.

#1 - Testing the functionality of the low water cut-off

All steam boilers have this vital safety device. Some are the mechanical type like the McDonnell-Miller #67 that have a drain valve piped on to bottom of it. Others are newer models that are electronic type that have a couple lights on the control.

Testing a #67 Low Water Cut-Off

Long Island PlumberIf you have a #67 type low water cut-off, its easiest to raise the thermostat to startup the boiler so you can check to see if the boiler turns off when you drain the boiler - thus triggering the LWCO.

Take a 5 gallon bucket and place it under the drain pipe. Slowly open the valve and allow water to drain out. Immediately to the left or right of the #67, you will see a skinny glass tube with a valve on top and on bottom. Give both of those valves a nudge. Just to free up the valves. Start turning “clock-wise” an 1/8th of a turn, then go back. (Do not touch the valves if rust or corrosion is present - you will do more harm than good - call a local licensed plumber for help)

Testing Electronic Low Water Cut-Off

Newer steam boilers have an electronic low water cut-off. These models have a brass probe threaded into the side of the boiler that attaches to a “black box” with a couple lights. Typically, to test these models the boiler does not need to be running. You should see a green light on the control that is always on. Another light will usually be red or yellow and only turn on when a “low water condition” is present - like when draining the boiler!

As you drain water into the bucket, you should see the water level in the sight glass start to go down. The water level will eventually reach a certain level and trigger the LWCO to turn off the boiler. If this does not happen, if water does not drain out or you drain more than 5 or 10 gallons of water and the boiler still does not turn off, call our local licensed Long Island plumber for a service appointment at the earliest available time.

If you do not check the low water cut-off monthly you risk having that device failing. If the LWCO fails, the boiler will eventually run out of water and, not knowing there isn't enough water present, will continue to operate as normal. When that happens, the boiler will literally cook to the point where the gaskets between the giant cast iron sections will melt away. Your entire home will smell like a burning tire factory and you will write a very big check to the plumber to replace your boiler. Worse case, it may also burn down your house. You've been warned.

#2 - Keeping the boiler clean

If you have a steam boiler, your house was build in the 1950’s or earlier, maybe much earlier. Therefore those black steel pipes in your home that has been carrying steam and water for 60-100+ years is slowly rusting away. Those fragments of deteriorating metal pipe are eventually making its was back to your boiler and you need to remove it.

Remember that sight glass I mentioned earlier? Ideally, you’d like to keep that water looking as clean as possible. Cleaner the water, more efficiently the system will run. More efficient the system runs, the cheaper fuel bills you will pay. Makes sense!

In closing, one final thought. Most systems have these automatic water feeder valves. You should hear them run 3 to 4 times a month. If you hear the valve add water more frequently you are losing water which is destroying your boiler. You will eventually “cut a hole” at the water line inside the boiler - resulting in a boiler replacement. If you do not have a automatic feeder, same applies for you too!

Do not add water more than 3 to 4 times a month during the heating season. Period.

Comments, questions, concerns? Email me!