How to remove air from your boiler system

Having air in your boiler system, also known as a hydronic heating system, is among the most common issues that you’ll get with a boiler. But the first issue you need to resolve is why you are having an air issue in the first place.

It’s normal, when you first commission a system, to get a little bit of an air issue. The reason behind this is that new water (H2O, the O part of it being oxygen), when introduced, has a significant portion of air in it. However, over time the air is slowly removed with automatic air vents, and/or an air scrubber. So, the very best type of water in your boiler system is actually dead oxygen-free water, which takes a period of time to accomplish.

The question is if your system is not new, if it is years old, and it’s developing an air issue, what causes that? One of the most common causes of it is a leak somewhere in your system, and new water is being replaced into the system, and with that new water comes new air. Another common cause is if you have a certain kind of piping system, commonly known as a polybutylene piping system, or a poly-b piping system, that absorbs air from the walls of the pipe. This type of piping system was banned back in about 2000.

The minor negative effect of having air in a boiler system is that it can make zones stop working. A major negative effect of having air in the system is that it can damage almost everything in the system and can make things rust out. This is because mixing air and water together causes non-ferrous or rustable metals to get destroyed. That often means the boiler itself will get destroyed. Boilers and boiler components rely on the fact that there is virtually no air left in the system and that allows them to not rust away.

So, as long as you’ve addressed the reason of why there is air in the system, getting the air out of the system can either be a simple thing or a complex thing. The first thing to look for is up on the radiators against the wall. Sometimes at one or either end you’ll see a little slotted screwdriver port. If you put a screwdriver in there and turn it about a quarter turn, it can open up, releasing the air.

At that point in time you must be sure that the air bleeds out and not a lot of water bleeds out, and that you turn the port back down so that water no longer comes out, as this can cause damage to your home. Releasing a little bit of air is often enough to unblock a zone from circulating water. That’s essentially what happens. Zones get blocked from water passing through because there is air trapped in the zone at a high point.

The more complicated way to get air out of a system to physically force it out and flush it out, with new fresh water. This is more complicated than it seems as it requires the boiler to be shut off, and certain shut offs to be turned off on the boiler system, to force the water through the exact zone that you want the water forced through. If it comes to that point, unless you are a HVAC technician, I would suggest that you call a company. There are many ways that you can damage your system at this point in time by doing the wrong thing.