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Differences between bladder and diaphragm pressure tanks??

Discussion in 'Irrigation' started by CRUZMISL, Aug 4, 2005.


    CRUZMISL LawnSite Member
    from zone 6
    Messages: 186

    Are there any significant differences (aside from drawdown capacity) between bladder type and diaphragm pressure tanks? The bladders are much cheaper and I'm wondering if this is a "get what you pay for" scenario.
  2. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Messages: 2,781

    Don't want to leave you w/o an answer here, but I'm not sure my answer understanding of this is the "best". The answer as I have always understood it was in the actual terminology. A diaphram is just that, it is a leather or rubber diaphram across the tank that creates an air chamber that is compressed "up" as the water pushes against it. A bladder tank has a "balloon" in it instead, usually connected to a schradder valve for adjustment, but it is possible for the entire tank to be filled if that "bladder" is allowed to deflate. The increased draw down on a bladder tank comes from the function of the bladder. The pressure on the bladder is from all sides. The location of the diaphram is "fixed" and means some wasted space from a drawn down perspective. As to one being "better" or more or less expensive. I think quality of construction/brand is what you want to watch for here along with the specifications for capacity.
  3. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,550

    I'd have to see the information the OP was looking at, before I could comment. The original Well X-trol tanks were diaphragm construction. I think their newer fiberglass Wellmate tanks use a polyethylene liner, in addition to any bladder or diaphragm. Manufacturing techniques may have more to do with whether there's a diaphragm or not.
  4. ZoneIII

    ZoneIII LawnSite Member
    Messages: 2

    I realize that this is an old post but I'm responding for the benefit of anyone else who may be interested in the topic. I'm no expert but I think there are some errors in that response. There is no air valve connected to the bladder as said above. The bladder only holds water. The air valve goes directly into the tank. It is the empty area (top) of the tank that contains the air. The bladder is only inflated with water and if it was deflated, the tank would NOT be full of water as stated. In fact, if it was deflated, the tank would have no water in it at all. It would just be filled with an empty bladder and air. Also, air does not surround the bladder. Air pushes down on the bladder which is located in the bottom of the tank. The air presses the bladder down to the bottom of the tank. The bladder is not like a balloon. It is a flattened cylindrical bag at the bottom of the tank. It appears that bicmudpuppy's understanding is the opposite of how this actually works. In other words, his reply indicates that he thinks the bladder holds air and the tank holds water. It's the exact opposite.
    Last edited: Dec 13, 2011
  5. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,550

    Well. Glad that got cleared up, and in the nick of time, too. ;)
  6. Kiril

    Kiril LawnSite Fanatic
    Messages: 18,334

    My eyes hurt.
  7. 1idejim

    1idejim LawnSite Fanatic
    Messages: 11,315

    mine too..........

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