Expansion Tanks - Are they all the same?

Alan (California Radiant) Forbes

Amtrol, Flexcon, Watts, Caleffi......................



When I order them, I usually go for the best price, but is one better than the others?  For either hydronic or potable applications, I'm sure the quality of the diaphragm makes a difference, no?

meplumber

Great question Alan.

I would like to hear the answer to that one myself.



I use almost exclusively Amtrol because that is what every supply house here carries. Unless the project's train driver (no offense intended to those of you PE's that are on here. I am referring to the "my degree means more than your 25+ yrs experience" engineers, that I seem to get stuck with all the time.) specifies something else.



Interested to hear from others.

lchmb

cant say

I cant say which is the best made now, however I can say I've had one on my own system for 22 years and only added 2lbs of air once. As of late though I seem to be replacing 3 tanks a week on service calls, most are only 5-10 years old if that...so thinking maybe there's an issue with quality..

hot_rod

two types

The common diaphragm which contains the fluid in the steel tank and the air, or nitrogen charge on the other side of the membrane.



For solar, a tank with the fluid in the steel vessel help cool the fluid and extend the bladder life. After stagnation conditions the tank can see a hot slug of fluid. Some expansion tank manufacturers offer an intermediate tank to help cool the fluid. It has a top and bottom tap to connect between the bladder tank and system.



The other style is a bag type where the fluid is inside the butyl rubber bag and the air in the steel vessel. I think the Taco CBX series is still a bag type.



Another option for a long lasting or maybe a lifetime version is the stainless steel tank. I spotted this "Baby Star" Italian version at a trade show in Canada awhile back.



I think Flexcon is offering a tank with a stainless steel nipple?



Temperature, quality of fluid, sizing, O2 ingress all play a part in an expansion tanks life expectancy.



hr

Jack

The only new tank

I am aware of is from Metlund. it is a "flow thru" design. The concept is self cleaning, or at least flushing. There is an inlet ttap and an outlet tap. When you think about how many expansion tanks "heal up" at the 1/2" mpt tap and if you've ever cut one apart, you can have some manky "stuff" in there, I think Larry may be on to something.

Ron Jr._3

What about

using potable expansion tanks on closed systems ?



Like lchmb , our servicemen have been replacing hydronic tanks that are less than 5 years old at an alarming rate . A few different brands .



But we routinely replace functioning tanks on boiler upgrades that are over 20 years old . Recently had one with a 1983 date code stamped in it ( Extrol 15 ) . This one was oriented above the pipe it was connected to , on the supply .

hot_rod

200F on DHW expansion tanks

for the max. temperature. At least on the Watts brand.