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Troubleshooting sponge filter

Discussion in 'Coldwater Fish and Ponds' started by Jim Sinclair, Feb 27, 2019.

  1. Jim Sinclair

    Jim Sinclair Fish Fanatic

    Oct 22, 2018
    Likes Received:
    Northeast USA
    Thank you for those detailed instructions. They were so descriptive that even I, with very poor visualization ability, was able to follow them and recognize what I was looking at when I opened up the pump.

    But when I opened it I could not see anything wrong with the diaphragm or flapper or anything else.

    I took it to my favorite LFS. The guy there spent about 20 minutes examining it and checking the different parts and exclaiming about what excellent condition the pump is in considering it's an old one that came with an old Craigslist aquarium. He said the diaphragm and flapper are in pristine condition.

    After removing and examining all the components, he put it back together and plugged it in. We could feel air blowing out of it.

    Then I thought perhaps the problem is not in the filter (which is working very well with a different pump), or in the pump (which appears to be in great shape), but with the airline tubing, which is not only old and stiff but has also been chewed on by cats. Maybe there were tiny micro-punctures in the tube which reduced the air pressure coming out the other end.

    With this possibility in mind, I came home and unhooked the brand new
    airline tubing from the brand new pump, connected it to the old pump which had just received a clean bill of health from the LFS guy, and plugged it in.

    And nothing happened. The filter works fine with the new pump and not at all with the old pump, with the same tube used on both trials.

    Do you have any other ideas that might make it possible to salvage this pump?

  2. AmandaN

    AmandaN New Member

    Jan 28, 2014
    Likes Received:
    Palmer Aquatics just did a pretty good hour long livestream talking about sponge filters in details. Maybe it will help you to understand.
  3. Colin_T

    Colin_T Member

    Jan 26, 2008
    Likes Received:
    Perth, WA
    Did they change the diaphragm in the pump?
    Diaphragms can be the right size and shape but sometimes they are too hard or soft for the particular pump. If you use a diaphragm that is too hard or too soft for that specific pump, it will run but not have any air pressure, (it won't be able to pump air to the bottom of a tank).

    If the diaphragm is attached too tight or too loose to the arm, it won't pump air properly.

    The air chamber has 2 flapper/ flutter valves in it, one on each side of the air chamber. Did they check both sides of the air chamber?

    Did they change the flapper/ flutter valves?
    These can look good but still let air leak through when they get old.

    If the air chamber and diaphragm look good, try putting a new air chamber and diaphragm in.

    I use to test air pumps at the shop after I changed things in them, just to make sure they worked so customers didn't go home and have to come back again.

    If everything has been replaced and it still can't pump air, the only other reason would be a drop in power going to the coil. If there is not enough power in the coil, the metal L shaped arm won't move fast enough and you won't get any air when the airline is in the water. However, the coils are normally pretty reliable because it is a non moving part and consists of copper wire wrapped around an iron rod.

    If there is a power drop in the pump there is nothing much you can do about it. If you know an electrician, you can get them to check the electrical side of the pump but if you don't know one, don't bother getting it tested because it will cost you more to have it tested by a sparky than it would cost to replace the pump.
    #18 Colin_T, Mar 3, 2019
    Last edited: Mar 3, 2019

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