Expansion tank location

I dont see why it would be a problem, as long as it wasn't elevated more than 65ft! then you would need 30psi to get the water up to it lol

No problems Huff. The folks across the pond place them in the attic of the home to conserve floor space all the time.

Another advantage of elevating your expansion tank is that you can use a lower initial air pressure in the tank itself to start your boiler system pressure at the nominal 12PSI that seems to be standard. If the tank was about 20ft. above the boiler you could start out with only a few PSI in the tank to maintain the 12PSI (cold) pressure at the boiler. That's assuming your boiler is at the bottom of the system. This means you can use more of the tanks total volume for expansion before it reaches whatever max pressure you want to limit your system to.

A bladder (diaphragm) tank has a limit to which the bladder can stretch so what I just said may not pertain to all models of expansion tank. Be nice to have someone who actually knows about these details to fill us in.

huffdawg said:

Good I think I will make a shelf for 2 expansion tanks and a 40 gal. dhw tank

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In the Amtrol installation literature they point out that the big tanks with the water inlet on the bottom should be situated such that air cannot accumulate under the bladder where it could cause corrosion.

I guess that means the piping going up to the tanks should go up to some sort of air vent before coming back down to the base of the tanks.

Wouldn't there be some air under the bladder regardless? I'm also thinking to locating up top.

maple1 said:

Wouldn't there be some air under the bladder regardless? I'm also thinking to locating up top.

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Not really, when the tank comes out of the box the bladder is pressed against the bottom. If piping comes down from the air separator and then downhill over to the base of the tank, then as the system is filled air should work its way up to the air separator and there would be little if any air under the bladder. So to heed Amtrol's warning all you have to do is have piping go continuously downhill to the base of the tank from some air venting point.

And by all means, put the tank up high. The higher the tank the smaller it needs to be, as someone has already noted. It's just that if you believe Amtrol's warning then need to prevent air from accumulating under bladder.

--ewd

OK, thanks, something else to keep in mind.

Big expansion tanks seem to be expensive - I had been thinking of laying down a smaller propane tank on top of my storage ones to use. I have a non-bladder one up between my joists on my existing system - it seems to work darned good, pressure stays pretty consistent & no problems at all in 15+ years with it. Now I'm wondering if I should bite the bullet on a bladder one(s) - in thinking mainly of doing all I can to keep air away from the system water. Seems every day I'm finding a new decision I'll have to make - maybe I'm spending too much time here (har).

huffdawg said:

So maybe I should tee off of the top of my buffer tank just before the float type air vent . Then from there, there would be a 2' drop to the expansion tank.
Is that OK.

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Should do the trick, or at least I hope so, since it's pretty much the same as mine ended up.

maple1 said:

Now I'm wondering if I should bite the bullet on a bladder one(s) - in thinking mainly of doing all I can to keep air away from the system water.

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A closed non-bladder tank should be no problem oxygen-wise. The oxygen causes some small amount of rusting at system startup, but once it is consumed you're good to go. And of course the problem of air under the bladder can't be a problem if there's no bladder.

If you go with a closed non-bladder tank then you want to encourage gas accumulation in the expansion tank.

Many of the old closed tank systems had a short dip tube into the top of the boiler for supply water, and then there would be another connection into the very top of the boiler that would pipe separated gas up into the expansion tank in the floor joists.

Others had a line that went from the air separator up into an expansion tank. Likewise it might work well to have a closed non-bladder tank above the boiler air separator. Instead of venting the air separator to atmosphere you could run a line up into the top of the expansion tank.

At any rate I'm not aware on anyone on the forum who is not happy with their home-brew expansion tank.

just because the "old-timers" did it that way doesn't mean it is right, I borrowed this book from a friend who does heating for a living before installing my new oil boiler, http://www.amazon.com/Pumping-away-options-hydronic-systems/dp/B0006PCBB0 the stuff he says is great, turns out my system had the pump on the wrong side, also I used the authors idea for bleeding a new system and it worked perfectly. this book is used as a textbook for teaching heating techs, it is just a short book with lots of diagrams and explains things in an easy to get way