gas steam boiler maintenance question (repost)

If there is excess solids already present in the water, a filter may help. Or, for some dissolved solids, such as hardness, VERY mild treatment may help. But if you are dealing with drinking water — you're fine.

Now oxygen… well,it's almost impossible to get rid of, short of distilling the water under inert gas. Right. The simplest way to handle that is to avoid adding any more water than needed, and to boil it right in the boiler.

However, some people do use distilled or deionized water for the initial boiler fill.

It is MUCH more important to avoid a situation where one is adding water in significant amounts — called a "leak". For residential steam boilers, anything much over a gallon a week is cause for real concern, and should be tracked down and fixed.

To be pedantic.

A filter will only remove solid material — clay particles, fine sand — and some are fine enough to remove bacteria, protozoans, and even virus particles. They will NOT remove any dissolved material.

Various ion exchange and adsorbent materials can remove some dissolved materials. Examples would be water softeners (will remove bivalent ations, such as Calcium ions and Manesium ions). Some ion exhange processes can remove other dissolved ions (potassium permanganate plus greensand for iron, for instance). Some adsorbents, such as activated carbon, will remove dissolved organics.

It is possible for some compounds to be added to the water to effectively remove oxygen — or, more exactly, to combine with it so it doesn't combine with something else. These come under the general heading of corrosion inhibitors, and most if not all of them are varying degrees of toxic.