Steam Boiler Water Removal (Advice)

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Aristotle Zoulas

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Hello, I understand that on a steam boiler with radiator system , one needs to remove some water on a monthly basis to help remove some debris from the entire system. My question is what is the best way to do this. My local plumber (licensed) recommended the following: With the boiler running, let water out into a bucket slowly keeping your eye on the sight glass. At some point the low water cutoff will be activated. This will turn the boiler off. A minute or so later, the auto fill valve will be activated and will automatically fill the boiler with clean water . This will happen in several stages as to prevent thermal shock. When the proper level is reached, the auto fill valve is deactivated and all is back to normal. The plumber recommended this method as this will test critical boiler components.

My question is this: if the low water cut off fails, does this mean you will burn out the boiler? In this particular case, the low water cut off kicks on after the sight glass is completely empty, is this normal? How much water is in the boiler at the point the sight glass is empty? Is it at a critical level? My main goal here is to make sure I am doing it right and moreover to prevent possible damage.

Many Thanks, Aristotle
 

Tom Sawyer

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First off, you never drain the boiler, you drain the sediment from the bowl of the low water cutoff. It has a spring close valve on the bottom. You only need to flush about a wurst of water from it maybe once a month. That's it.
 

hj

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There is no "thermal shock" if the boiler has water in it, because the new water flows in below the water level and mixes with it IMMEDIATELY. When the water feeder is activated it feeds water until the proper level is reached, it does NOT feed, stop, feed, stop, etc. The low water cutoff, should also feed the water, but if you are draining the water through a boiler drain valve, you may be draining it faster than the feeder can replenish it which is why the sight glass empties. Opening the LWC drain while the burner is operating will test both the water feed and LWC operations. If the LWC does not work, and the pressure relief valve does not open, then boiler may be destroyed, OR you house could be blown up when the boiler cracks.
 

Tom Sawyer

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Quart of water. HJ is correct. Draining water from the LWCO both flushes the sediment and tests the switch at the same time if the burner is running. In no case should you be draining anymore than perhaps a gallon from the boiler because very time you do, you introduce oxygen and contaminates that can cause the boiler to surge and make wet steam which will hammer in the piping.
 
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