End of Heating Season - What about the boiler?

You’re heating your home with radiators. Good. That means you’ve got a boiler.
It may make you happy to know the end of the heating season may very well be upon us and you may have some questions about what to do with that big fuel burning, carbon monoxide producing, money-swallowing appliance in your cellar.
Should you just turn your thermostat off or down to 50° or so and signal the boiler that you’re done with it for the next few months? That’s one way you could go. Should you turn the safety switch off at the top of the cellar stairs or at the boiler itself? That’s a surer way to keep the boiler from firing up and a sound method of dealing with a season change, but what if you’re a tinkerer or you’re looking for a next-level maintenance procedure for keeping the boiler around a few years longer?
Follow this line of thinking.
When boilers fail it’s generally an issue related to the electronic parts that make them work safely and automatically. Repairs like those involve a good troubleshooter who pinpoints the issue and doesn’t change all the parts on the boiler 1-by- 1 until it runs again. In my shop, technicians in the know call those guys the “Parts Changers”. Parts Changers follow no specific mechanical troubleshooting process. They just change parts and hand you a bill once the fire lights up.
Now, if you’re lucky enough to find a good boiler technician then ask him or her about what to do with a boiler at the end of the heating season. The inconsistencies in their answers, even among the best of them, might surprise you.
It seems there are two or three schools of thought on the subject. One is to leave it alone. Just shut the thermostat or the power switch off and walk away. The idea here is that there aren’t many user-serviceable parts on a boiler and giving homeowners permission to delve into the boiler beyond the power switch is just asking for trouble for both you and your service provider. Sure, you could pay a qualified technical company to come and do something a little more in-depth, but you’re going to have your boiler for something like 25 years. You’re probably already paying for a seasonal startup visit. How much do you want to pay in elective service calls over 25 years to try to extend the life of your boiler another 5 or 10? The reality is that after 20 years, most boilers suffer a great decrease in efficiency and keeping them much longer than that amounts to a lot of wasted fuel dollars, even though the boiler seems to be in tip-top shape. So, keeping maintenance costs manageable should be a goal for any household or building.

Another school of thought is the idea of manually shutting off the water feed pipe and draining the whole boiler. The thinking here is that the boiler’s cast iron is most likely to fail at the “water line”. The water line is a term we use when talking about a steam boiler. It’s the level in that vertical glass tube which is consistent through the whole boiler and ground-level piping system. At that point, the water level and fresh oxygen meet to combine a mix of elements that is corrosive to the boiler’s cast iron components. This makes the boiler itself, not the very replaceable external parts, vulnerable to premature failure. So, you have the option to drain the boiler. The problem with this is that you can’t check, and you’ll rarely every have the means, to drain the boiler completely. That means water sitting in little pools in the bottom of the boiler all season long. That can’t be good.
What’s left? Many technicians and some boiler manufacturers prefer to have the boiler filled to its very top and even a little beyond. If you can figure out how to get water just a little higher than the boiler and into the nearby piping without getting into the radiators, then you’re a next-level DIY’er.
This a sound and obvious method of eliminating that water line because you’ve pushed it out of the boiler and up into the pipes just above the boiler. A water line leak at the steam outlet pipe, first of all I’ve never seen one in over 30 years in the service business, would be far less costly and easy to fix than a water line leak inside the boiler.

No matter what you do with your boiler, there is one thing to avoid and that is fresh water.
Fresh water is very oxygen rich. Tiny bubbles of oxygen swim around between the water molecules and attack things like ferrous metals in which they may make contact and so the water that sits in your boiler is best and least corrosive after it’s been heated and that oxygen has been boiled out.
You see, in simple terms, hotter water releases oxygen whereas cooler water tends to retain it.
What that all means is that any time new water is added to a boiler, especially an old-school cast iron steam or hot water boiler, the water should immediately be made as hot as it can safely be made so that it is quickly made less corrosive than it was when it was introduced to the system.
Hope this helps and thanks for reading.
John Cataneo
Master Plumber
License #1784
www.72fLLC.com