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  1. #1
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    Mar 2007
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    Default Old Style Expansion Tank

    What do you tell clients when you run across the old, non diaphragm, type of boiler expansion tank? Get rid of it, leave it unless the pressure is too high, etc?

    I get about one a year, usually on a 50 year old baseboard system.

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    Jim Robinson
    New Mexico, USA

  2. #2
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    Maryland
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    Default Re: Old Style Expansion Tank

    The tank will work fine until it rusts out, provided that it is maintained. In that it has to be drained as part of a maintenance scheduled. Other than that the old, non diaphragm, type of boiler expansion tank is fine. The one in your picture looks relatively new. So remaining life expectancy (depending on quality) may be 40+years.


  3. #3
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    Default Re: Old Style Expansion Tank

    Yes because there is no bladder like modern tanks the tank will become water logged.

    Thats why as Garry points out it should be drained and refilled.


  4. #4

    Default Re: Old Style Expansion Tank

    those old tanks can last 60-100 years, it depends on who made them and local site conditions. Unless there are signs of issues I would simply state what it is in the report, recommend further monitoring and leave it at that...it will certainly outlast today's replacement expansion tanks. Also even though it looks new it surly is not, they can be painted easily and made to look new.

    Jeff Zehnder - Home Inspector, Raleigh, NC
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  5. #5
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    New Mexico
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    Default Re: Old Style Expansion Tank

    Not new, original to house so about 45 years old. How often should they be drained? And do you mean drain 100% of it, or just drain off some of the water? For my education, what does draining accomplish? Won't it just refill after it's drained out?

    Jim Robinson
    New Mexico, USA

  6. #6
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  7. #7
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    Jul 2008
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    Default Re: Old Style Expansion Tank

    This looks like a case of "if it ain't broke, don't fix it". Those old style expansion tanks have been around (as the OP stated) for years and as good as that one looks why bother?

    Any heating system needs maintenance, I'd say in your report that this one does too and leave it at that.


  8. #8
    Join Date
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    Spring City/Surrounding Philadelphia area
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    Default Re: Old Style Expansion Tank

    Those type of tanks are as common around here as crappy chimneys. I make no recommendation about them (the tanks that is, not the chimneys). I simply explain their purpose. I have rarely if ever seen a problem with them.

    "It takes a big man to cry. It takes an even bigger man to laugh at that man". - Jack Handey

  9. #9
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    Feb 2009
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    Default Re: Old Style Expansion Tank

    Here's a problem I had with my expansion tank only 2 days ago.
    Boiler systems are not common here, so I was waiting for the learned members to comment. Unfortunately, I'll have to be satisfied with this bunch.

    Directly below the 40 yr old expansion tank is a 4 yr old water heater with a trickle of rust coming out or it. The pics tell the story.

    (Did you know? The electric screwdriver is also a 1/4" nut driver? Handy.)

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  10. #10
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    Default Re: Old Style Expansion Tank

    I'll have to take a look for that isolation valve mentioned it the Inspect NY article. I don't remember seeing one on any of the old tanks that I've had. Do you guys see that valve often?

    Jim Robinson
    New Mexico, USA

  11. #11
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    Default Re: Old Style Expansion Tank

    The makeup water comes in at the lower left of this pic, thru a one-way check valve. Is that the one you mean? Yes, there should always be one of those.

    This system had 3 thermostats.

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  12. #12
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    Default Re: Old Style Expansion Tank

    Friedman has this on his web site:

    Turn off the isolating valve that should be located on that hot water feed pipe between the expansion tank and the boiler or heating line. This temporarily isolates the expansion tank from the rest of the hot water heating system. If you don't do this and you start draining the expansion tank you may end up draining water from your heating piping too - not what you want. We only want to drain the water that is inside the expansion tank. In our photo at left the blue arrow points to the isolating valve.

    I don't know that I've seen that isolation valve, but I wasn't specifically looking for it.

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  13. #13
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    Default Re: Old Style Expansion Tank

    On this oil-fired boiler system, the isolation valve for the expansion tank is a red and white handle on the right. That pipe goes up and over to the expansion tank.

    To the left of the boiler, abandoned double oil lines could be from a buried oil tank. Pumped systems have a return line. The present tank is above ground gravity feed, just one line coming in on the right.

    Also on the right, the screened opening provides combustion air for the furnace room.

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  14. #14
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    Default Re: Old Style Expansion Tank

    Jim,
    You may not have an isolation valve that isolates the tank from the incoming water.
    In theory the water supply to the boiler should restore water to the system before it sucks air from the tank. But it is possible that yo may get air into the system from the expansion tank. So the system will need to be bled, which should be done anyhow as part of an annual maintenance. Which is the answer to the draining of the tank.... Annual...

    You drain out the water in the tank to create a volume of air that will act as a cushion to the expansion of the water in the system.

    The problem with the tank in your picture is that the bib valve is nice in that you can connect a hose to it and control the water as it drains. The problem is that the tank needs an air supply to allow it to drain. Resulting in a a water cooler effect where air is sucked up the drain line into the tank to allow it to drain and it can take a while to drain.

    Everyone has their method to drain the tanks. My preferred method, because it is quick ( 45sec or less), is to remove the plug (in your case the valve) and with a trash can under tank (i use a dolly platform under trashcan so I can move it later) stick a 4ft piece of 1/2" PCV up into the tank. The result is that the water comes rushing out of the tank and into the trash can. And yes it can be a little messy with splashing water. But after doing it a few times you get the nack of doing it with just a little water missing the trash can. Then replace the plug. Roll the trash can to the sanitary tub and bail out the water till you can dump the can into the tub. Total time involved with tank, maybe 3min.


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