Lifespan of newer bladder based expansion tanks?

zeb2000_2

A question I Have- Can a bladder tank be charged up with nitrogen? Would that be better than air?

Al Roethlisberger

Lifespan of newer bladder based expansion tanks?


I had asked this as a piggy-back question in another thread, so I thought I'd break it out here.

Question: How long are we seeing modern bladder-based expansion tanks lasting, especially larger units?

I have an old air-cushion tank, about 30G, that likely needs to be replaced. So I was looking at a new bladder tank, but had some concerns about longevity.

Thanks,
Al

Derheatmeister

2 PSI less... HM

Check why Question on the other post about the 2 psi less

hot_rod

properly sized

and installed thy should last 15, 20 or more years. Mounting them in the correct position is important. Adjusting the pre-charge pressure, of course. Older non barrier radiant tube systems would eat through expansion tanks at an alarming rate, often in a few years time.

hr

NRTDave

Thermal isolation...

With the caveat that I am neither a pro or an engineer, I'd still try and put enough piping in between the system and the expansion tank so that the water near the expansion tank isn't changing much. Heat expansion cycles are seldom good for anything, and I can't see rubber bladders being an exception.

D107

Corollary: How often to check tank pressure?

This is one maintenance issue I bet is rarely addressed, sort of like how often are indirect HWHs cleaned out. Around LI the answer to that question would usually be 'if it's working OK leave it alone.' I believe they have to be disconnected to test(?), and lifting those full tanks is no easy feat.

Thanks,

David

Derheatmeister

I Install an shut off and an Drain so that the tank can be drained to check the Bladder in an relieved state..

No need to remove the tank for the check...

scott markle_2

HR,

By properly sized I assume you mean big enough. No harm in over-sizing is there? It's a bit of work to figure out the exact water volume of a system in advance and I'm inclined to oversize unless there is a real space issue.

As far as position ( up, down or sideways) , is there a an explanation for why this is important? UniR says locate at distance from the main flow but I recall hearing otherwise (not at the end of a dead end line) . Then there is the question of the zero pressure point. Contradicting this wisdom Viessmann makes a special note about locating the expansion tank at the outlet side of the vitodens.

The boiler drain and isolation valve make sense for checking tank pressure, but un-screwing the tank is not such a big deal, it depend on how important you think annual monitoring of this is.

Derhetmiester, do you find much loss of pressure in the tanks you check annually? How about circulators, do you find many drawing excessive Amps? (you get what you pay for!) how many points on that service check list of yours anyway? BTW have you cleaned your fridge coils with compressed air this season? mine are way overdue.

Big Ed_4

Expansion Tank

The bladder type expansion tank should be hanging down to stay wet so they Dont dry out.

The point of no pressure change is the pipe conection of the tank to the system. At this point is the best location for the pressure reducing valve.


If you get increase of pressure on temperture rise you need a larger tank.





What is amazing is the old flair tanks we installed in the '70s. They were longer slender tank. They were the longest lived bladder tanks I still see some out there.

hot_rod

bigger is better

when in doubt size up.

Solar systems really benefit from oversized expansion as the temperature swing can be so large. It possible for a flat panel to reach 325-350F, even higher on evac tube systems.

You'll notice expansion tanks on the return side on solar pump stations so they see cooler fluid temperatures, after the trip through the HX.

Here is a clever expansion tank fitting. It's a double check valve. One side keeps fluid in the system, the other allows you to remove the expansion tank and keep the charge in it. It also has a notch to fit into the heavy steel angle bracket. It comes with the Caleffi solar expansion tank kit. Right now it has a 3/4 tank thread connection, only.

hr

Mike T., Swampeast MO

Most certainly! Search for a recent post by Brad White on just this topic.

Nitrogen is effectively inert and will have not affect the bladder. "Air" on the other hand contains oxygen with that nasty little habit of oxidizing other things... Such keeps us alive, but it kills many of the things we make. With a well sealed, well-designed fluid-side system (where oxygen stays dissolved), proper tank sizing and nitrogen on the "air" side, something tells me that modern tanks might last nearly as long as the c. 1922 plain steel tank still serving perfectly in my basement. (Of course it has a B&G Air-Trol fitting to ensure that the air inside of it STAYS inside of it...)