Modify old pressure tank for expansion tank?

[wsurfer49]

I am just assembling components to begin installation of my Econoburn 100 and am wondering about the possibility of using an old 30 gallon pressure tank minus the bladder as an expansion tank. I have 2 and would need the second when I eventually go to 500 gallon storage. It seems that the tank would be pretty easily modified and although the bladder would be nice I doubt that it would take the high temps. Any thoughts or experience would be appreciated.

 

[in hot water]

The purpose of the bladder in a hydronic expansion tank is to keep the air (O2) and water separate. With a plain steel tank, also known as a compression tank, you will need to replace the air from time to time as the hot boiler water will sip it out and vent it out your air eliminator device.

Typically those older compression tanks had sight glasses to see where the water/ air level was. They also used an Airtrol fitting that put any vented air back up into the tank. You will need to know where the water level is when you fill the system to assure you have enough "bubble" for expansion purposes. An air fitting on the top would allow you to replenish the air. Keep in mind every time you add air you add fresh O2 that aids corrosion in the system.

Will it work, sure, but it will take some maintaining, and a boiler inhibitor with a O2 scavanger would be good insurance. Or bite the bullet and get a bladder expansion tank

You can tee together multiple tanks if you find a deal on smaller sizes. Tee them all into the same location on the system the inlet side of the system pump, ideally.

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