Expansion Tank Life Span


  #1  
Old 09-20-04, 05:03 PM
Snowmoman
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Expansion Tank Life Span

Just came home from a vacation to find another leaking expansion tank on my oil fired system. The tanks don't seem to last longer than 3 or 4 years, sometimes only 2 years. Is this considered normal? I've tried several brands, and they all either leak at the seam or spring a pin hole. I have well water that is filtered as it enters the house. The filter catches some sediment, but I wouldn't say I get much, it only needs to be changed 2 times a year. Any help would be great.
 
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Old 09-20-04, 10:52 PM
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Expansion tank Life

An Expansion tank should last a lot longer than that, Do you have a leak in the system so that fresh water (and oxygen) is coming in all the time, I've seen thin pressed steel radiators still good as gold after 30 yrs. I have replaced very few tanks in my 40 yrs experience on heating system. Last one last yr was 15yrs old.
A Ex tank should be installed so that hot water does not get back into the tank.
so this means the pipework from the system to the tank should be as long as possible, of Copper (so it helps to cool before it gets to the tank.) and NOT insulated, This very important if it's a bladder tank.
Wonder too if it happens to be a bit on the small side. What the difference in cold to hot pressure? If it is more than 5 psi it probably on the small side. I preferr to err on too big side rather than being on the small side.
 
  #3  
Old 09-21-04, 05:40 PM
H
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Switching...

Try a conventional expansion tank instead of the air cushion style. This has no air bladder and found on most commercial installations. Have the boiler water PH tested. If this is eating your tank, think what it might be doing to the cast iron sections of the boiler? Fix the water problem before the damage is final to the expensive components.
 
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Old 09-21-04, 10:32 PM
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Expansion Tank

I doubt that it would be the water as once it been heated it loses all the air and becomes passive, Unless there is fresh water being introduced into the system all the time you should not get any corrosion. If the water was the problem it would be taking the lining of your stomach every cup of coffee you have.
Is the tank situated so that there is no air in the tank (ie the connection should be at the top.) so there is no AIR whatso ever in the tank or anywere.
If the tank connection is at the bottom air can be trapped in the tank and with the moisture from the water pushing into the tank when the system is hot, and then back out again when cold.
Water is NOT corrosive, BUT Water & Oxygen are corrosive. Air is around 20.9 to 21% oxygen.
 
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Old 09-23-04, 04:16 AM
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Might be, could be...

Your best bet is to contact the manufacturer about this as they are the ones that should be standing behind the product. An inexpensive test is to use Hydrion Paper, Much like litmus paper, available from the local drug store or chemical supply store to test the PH, but the ultimate test is to install a water meter to the feed line and see how much water is used per month. If more than about 6 gallons, the boiler is in danger.
 

Last edited by hvac01453; 09-23-04 at 04:27 AM.
 

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