Expansion Tanks die too fast

KCA_2

Good morning guys. It seems like I’m replacing expansion tanks on hydronic systems. Way too fast. I just replaced one that was installed in 2020 and it’s already leaking. Or the diaphragm has already been degraded or has a hole in it. Is this just a matter of Poor manufacturing or is there something I can do to make these things last longer. On the other hand I’ve seen expansion tanks that are 30 years old that work. 

GGross

Pictures of the piping and overall installation would help. While the occasional manufacturing defect or shipping damage may occur, standard amtrol expansion tanks have a 7 year warranty. If you see one failure, chalk it up to bad luck, you have more than one in-warranty failure and there is something system related happening.

JUGHNE

I have this half baked theory that the larger the tank (over sized) the membrane has to flex less.

So if an expansion tank is just barely big enough, the membrane will have extreme movement and quite often. A size or two "oversized" will be worked less.

More so, I believe, with private water well storage tanks which are required to work constantly. (cuts down on pump cycling also).

JakeCK

I oversized my tank when I replaced it... No such thing as too big of an expansion tank. 

EBEBRATT-Ed

The bladder tank in my house was there when I bought the place (Amtrol tank). I lived there 32 years and the tank finally failed. No leak,,,bad bladder.

I agree with @JUGHNE if anything oversize the tank is cheap money especially on a residential job

HomerJSmith

You might tell us what the size of the tank is and the manufacturer. The fill size of the sys is important, too.

Big Ed_4

Expansion tanks should be piped down and wet . Air trapped in the tank will rot the inside of the tank . The bladar can rupture moving over the rust. ...

hot_rod

The tank itself leaking, or a failed diaphragm?

There are some stainless steel tanks available. Amtrol has a new pro series, supposedly heavier rubber component, longer warranty??

Mad Dog_2

I've seen this All too often in the last 15 years I'd say - with ALL the companies. You are lucky to get 4 or 5 years out of them where they used to last 20. This is on Potable and Hydronic applications. An isolation ball valve with brass tee and boiler drain between the valve and the tank is NICE to have when you are changing them this often. Mad Dog

GGross

@Mad Dog_2

I think it's confirmation bias. We might process 3-5 Amtrol warranties per year and sell between 500-700 each year. It's a seven year warranty so if they failed in 5 years due to defects they would just be throwing money away on warranty. I have never one time been denied a warranty from Amtrol either

KCA_2

Hey guys, thanks for all the responses. Short of just out and out rusting I think you’re correct in wanting to oversize the tank. I’m on projects where I don’t know what the fill is I can guess I suppose but I honestly don’t know what it is. So I think I’ll go ahead and just go with the next size up if I’m able to sometimes there’s installed so tight you can’t but I like the idea.  I’ve seen tanks piped up and you’re right about the air trapping & the rust. Not a lot I can do with that other than repiping it. But usually I’m just out on troubleshoot and repair. The owners don’t want to pay for re-piping. I do appreciate all your comments.  😊

Kickstand55

I mentioned this before in another post where chlorides are being added to municipal water systems causing rubber components to break down. This goes for domestic and hydronic expansion tanks as well as toilet flappers.
I see this frequently in the Manchester, NH water system.

Jon_blaney

You need to be sure the tank pressure matches the system pressure. Sometimes the installer does not check.

leonz

A replacement fifteen gallon Steel Compression Tank with an Airtrol Valve can be hung in the ceiling joist and connected the existing air scoop.

It does not have to be directly over the boiler either as long as it is above the boiler as the pipe or Pex hose is simply sloped up to the airtrol valve to let the air bubbles rise up to the steel compression tank.

A fifteen gallon Steel Compression Tank will have a five gallon air volume and a 10 gallon water volume to provide plenty of system pressure without a bladder or requiring the system to have an open auto fill valve.

The Steel Compression Tank has no bladder to rupture or leak and the Airtrol valve has no moving parts nor does it require you to pre-charge it.

The steel compression tank should have a gauge glass mounted in the 2 end tapping's of the Steel Compression Tank to aid in water level monitoring and the airtrol valve to enure the tank is filled to the proper water level by draining excess water if needed.

If the home is a slab on grade home an open to air steel tank with a gauge glass hung in the ceiling above the boiler is even simpler as the weight of the water maintains the point of no pressure change with no fuss or muss or bleeding radiators.

Mr. Holohan has had a steel compression tank in his home for many decades to maintain the system pressure and point of no pressure change in his heating system. It is hung in the ceiling above his boiler like mine is and is quiet and takes in the microbubbles and lets cool water enter back into the boiler when needed using gravity.

A big thank you to the Dead Men for using gas law to create a simple heating system.

Jamie Hall

I like your comment, @leonz ! The building I maintain which has hot water heat (NOT Cedric!) has a steel compression tank. Installed around 1930 or so. Simple, reliable, no moving parts, no muss, no fuss. What's not to like? Except that modern hvac people and plumbers don't understand them and put air removal devices on the system, which defeats them...

Jamie Hall

ron said:

why is it the norm now for expansion tanksto have a bladder inside?

I mounted my x-tank "upside down?" so that if the bladder does leak the tank is not catching water. As such, how would I ever know my expansion tank goes bad?

Expansion Tanks die too fast - not the only thing these days

They can be less expensive and smaller than compression tanks, and can be installed more flexibly -- and by people who are clueless about how compression tanks work.

If the bladder leaks, the tank will lose its air precharge, which is required to make it work. It will still sort of vaguely work, but will behave like a much smaller tank. You will know pretty fast if it fails -- the system pressure will swing much more between on and off, and it's very likely that you will wind up with a good size puddle on the floor from the pressure relieft valve or no heat on the upper floors. Or both.

hot_rod

Many of the smaller tanks are diaphragm type, a rubber fins across the center. These have a smaller capacity compared to bag or bladder style

With a bag type, fluid is inside the rubber bag. The bag can expand go almost the entire size of the steel shell.  

So the fluid does not touch the steel vessel, And you get a larger acceptance

Probably a higher price. I have seen them in small# 30 size

Big Ed_4

Just like the domestic thermal expansion tanks ?

leonz

ron said:

why is it the norm now for expansion tanksto have a bladder inside?

I mounted my x-tank "upside down?" so that if the bladder does leak the tank is not catching water. As such, how would I ever know my expansion tank goes bad?

Expansion Tanks die too fast - not the only thing these days

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Hello Ron,

I am speaking as a homeowner with a 15 gallon steel compression tank to maintain the point of no pressure change in my hot water baseboard heating system.

If I remember some of Mr. Holohans writing correctly about the history of the bladder expansion tank they were an outgrowth of the slab on grade homes built by Litton?, massive cookie cutter tracts of less expensive housing built for veterans after WW2; and how soft copper hot water in floor heat was used as they had less room for boiler plumbing and no basements and needed a way to maintain system pressure and they used dry ice in the bladder tank to maintain the precharge-I may be wrong about the sequence of things here; but they developed the design of bladder tanks over time and they work; and sadly they do not help to maintain the system pressure by water weight alone like my 15 gallon steel compression tank.

ME, I am happy I no longer have to bleed my (*&^%$^& baseboard heat which I hated to do; and I do not have to stress my replacement knees.

If you can convince them how a Steel Compression Tank or Steel Open To Air Saddle Expansion Tank is much better for them by explaining how these tanks do not require an autofeed valve to be left on which is a problem if there is a leak especially if you have a well for a water supply and how the additional water weight aids in maintaining the point of no pressure change and by simply turning up the thermostat at the start of the heating season is to assure that there is no air in the system I am all for it as heating the water the very hot water will drive the air bubbles out of it and into the Steel Open To Air Saddle Tank or the Steel Compression Tank.

Good solid joist lumber and pipe straps or a strong hanging shelf made to support the open to air steel expansion tank with the airtrol valve and gauge glass or the steel compression tank with the airtrol valve and gauge glass and an existing air scoop piped to the airtrol valve with pipe or pex and fittings is all that is required.

AS long as the water with the bubbles slugs and microbubbles can escape and rise to either of these types of tanks you have heat.

Both a Steel Compression Tank and Open To Air Steel Saddle Mounted Expansion Tank can be used to replace a bladder expansion tank on a slab on grade heating system.
Both types of tanks require an airtrol valve to work properly to maintain the point of no pressure change and can be connected to an air scoop tapping.

The steel compression tank is better used with a heating systems boiler in a basement as an open to air saddle tank will spill over due to the water weight above it.

The larger the open to air saddle expansion tank or larger steel compression tank the more effective the heating system will be too.

A big thank you goes to Mr. Dan Holohan, a Bigger thank you to the following books-CLASSIC HYDRONICS, HOW COME, PUMPING AWAY and an even bigger thank you goes to the DEAD MEN, GAS LAW and the fundamental Laws of THERMAL DYNAMICS.

leonz

Jamie Hall said:

I like your comment, @leonz ! The building I maintain which has hot water heat (NOT Cedric!) has a steel compression tank. Installed around 1930 or so. Simple, reliable, no moving parts, no muss, no fuss. What's not to like? Except that modern hvac people and plumbers don't understand them and put air removal devices on the system, which defeats them...

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An aquaintance of mine who has an Axeman Anderson 260S coal stoker with a large trombone type domestic hot water coil and is heating a two family farmhouse with Cast Iron Radiators ran into this issue when the old fuel oil boiler was replaced.

The plumber he hired replaced the old boiler with the new oil boiler and installed an air scoop, automatic air vents, bladder expansion tank , circulators and controls and come the start of the heating season he and his sister inlaw next door had no heat and no idea why he had no heat until I convinced him to purchase copies of CLASSIC HYDRONICS and PUMPING AWAY and I explained that the automatic air bleeders on the boiler drained all the air out of the system and the water auto feeder flooded his steel compression tank.

As the domestic coil in the coal stoker was old and leaking he replaced it and the wear parts on the coal stoker and installed ball valves to separate the two boilers and removed the automatic air vents and the bladder tank on the oil boiler and in so doing the oil boiler depends on the steel compression tank for the point of no pressure change when it is operating and the coal stoker is not operating.