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  1. #1
    Banned Rank = Mature Champion Trace's Avatar
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    T-Tip#11 DIY Air Pump Pressure Release Control.

    Back pressure in a pond Air Line over about 0.2bar makes the pump work harder than it should and parts can wear out a lot faster.

    Back pressure can be decreased by using as big an ID (Inside Diameter) bore as possible in the tubing in all parts of the system from the piston/diaphragm onwards.... anywhere this bore is reduced e.g. screw in hose tails, 4mm manifolds, air stones with the tiny 2.5mm inlets, pumping to depth in the pond etc. etc. ... will increase the back pressure and it all adds up.

    You can hear a pump labouring harder with increased back pressure ... if you stick your finger over the pump outlet you'll see what I mean ...

    Some places sell expensive pressure release valves: Air Pressure Relief Valve

    But these are ridiculous prices and still running your pump at the limit ...

    What I did here to optimize the system was:

    Checked the pump internal bore which was 8mm ... this then reduced to 6.5mm at the outlet so I drilled it out to 8mm, I then use full bore pneumatic push fit 12mm OD fittings and tubing for everything else downstream so the entire system now is mostly 8mm or larger bore.

    I drill all air stone Inlets larger ... e.g. 8mm ID pipe stones I drill out from 2.5mm to 7mm ..... 4mm ID pipe stones I drill from 2.5mm to 4.5mm.

    It's amazing the difference this makes in the amount of air pumped to any given depth.

    I then incorporate a DIY Flow Controlled vent which is much better than a fixed pressure release valve to make sure the system is using the lowest amount of back pressure to do whats required from it ... and put a dry air stone on the end of this to silence the hiss from venting air.

    Here's an example diagram of position.



    The worst back pressure offenders are the 4mm manifolds that fit straight onto the pump ... I'm sure these are just included to increase sales of pumps and diaphragms.

    With a back pressure optimized system it's amazing what even a small 30LPM pump can actually manage .... and you'll get maximum life from all components ...

    Here's a practical example of how I use a Flow Control Vent:



    This was a very simple manifold to balance just two 4mm lines driven with a large pump.

    The usual mistake people make is to restrict the 4mm lines at the taps on each line ... and this does work for controlling the amount of air released from the stones on the end of the 4mm lines .... BUT this also massively increases pump back pressure and puts excessive stress on the pump components.

    The best way to do this is not to Restrict Flow ... but to Vent it to the atmosphere instead using a push fit pneumatic Flow Controller (much, much better and more precise than a quarter turn tap valve) and stick a drilled out dry Air Stone on a short piece of tubing on the end of the Flow Controller to silence the venting air.

    The small taps are used to balance the 4mm line Outputs against each other and the Flow Control Valve is used to control the overall amount of Air Pressure you need (all the excess is vented) ... So using this method you know you are running the system at the Minimum back pressure for any given requirement.

    For an air stone vent silencer you can just use the cheapest 2" air stone you can get but cut off the thin part for 4mm tubing and drill out the thicker part to 7mm (increasing drill bit size rather than going straight for the 7mm bit).

    Here's a pic of a before and after air stone ... before inlet size = 2.5mm ... after size = 7mm



    ***Tip*** Even when using 4mm tubing I carefully drill out all my stones from 2.5mm to 4.5mm ... makes a huge difference to the amount of air pumped to any given depth ....



  2. Thanks apbarr, Manky Sanke, GeorgeReid, Andre Asagi, Chipmonk, dmsims Thanked / Liked this Post
  3. #2
    Extreme Koi Member Rank = Grand Champion Andre Asagi's Avatar
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    Thanks Trace. One query....

    You said...

    "
    What I did here to optimize the system was:

    Checked the pump internal bore which was 8mm ... this then reduced to 6.5mm at the outlet so I drilled it out to 8mm.....
    "

    How do we establish what bore our air pumps are?

  4. #3
    Extreme Koi Member Rank = Grand Champion Andre Asagi's Avatar
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    Double post Itchy trigger finger but a stable turntable.
    Last edited by Andre Asagi; 17-01-2017 at 06:06 PM. Reason: Double Post

  5. #4
    Banned Rank = Mature Champion Trace's Avatar
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    Quote Originally Posted by Andre Asagi View Post
    Thanks Trace. One query....

    You said...

    "
    What I did here to optimize the system was:

    Checked the pump internal bore which was 8mm ... this then reduced to 6.5mm at the outlet so I drilled it out to 8mm.....
    "

    How do we establish what bore our air pumps are?
    I took the cover and base off and checked the internal piping from the diaphragms ... this was all 8mm till it got to the Outlet where it reduced to 6.5mm ... so I drilled it out to 8mm and there was a noticeable improvement in output. The 6.5mm decrease is probably designed in to increase back pressure to shorten diaphragm life ...

    Depending on what pump you have it may or may not be as easy to check out the inside ...

  6. #5
    Extreme Koi Member Rank = Grand Champion Andre Asagi's Avatar
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    Trace, what make/model of air pump was this?

    *Hopes it's Hailea ACO-9730 so i don't have to take mine apart to check*

  7. #6
    Extreme Koi Member Rank = Grand Champion Andre Asagi's Avatar
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    ....and how do you actually establish whether it's 6mm or 8mm? Do you have a measuring device?

    PLEASE, nobody say "Yeah, it's called a ruler".

  8. #7
    Extreme Koi Member Rank = Grand Champion Andre Asagi's Avatar
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    Oh....and what happened to T Tip 4 & 8 ?

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  10. #8
    Banned Rank = Mature Champion Trace's Avatar
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    Quote Originally Posted by Andre Asagi View Post
    Trace, what make/model of air pump was this?

    *Hopes it's Hailea ACO-9730 so i don't have to take mine apart to check*
    I use ACO 9810's (which are the same inside as the ACO 9720 in a different housing) ... 9730 is slightly different housing yet again if it's a green one. I use 9810's as when you reduce all your back pressure restrictions as detailed above you can use smaller pumps.

    Don't take it apart just measure the Outlet Internal Diameter.

    ....and how do you actually establish whether it's 6mm or 8mm? Do you have a measuring device?

    PLEASE, nobody say "Yeah, it's called a ruler".
    You can do this with drill bits if you have a full set of sizes ... or yes you can resort to the use of a boring old ruler ...

    Oh....and what happened to T Tip 4 & 8 ?
    Good question .... T-Tips#'s 4 & 8 ... are Health related ... so are on the Health & Medication forum ...

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  12. #9
    Senior Member Rank = Hassai dc197's Avatar
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    Quote Originally Posted by Andre Asagi View Post
    ....and how do you actually establish whether it's 6mm or 8mm? Do you have a measuring device?

    PLEASE, nobody say "Yeah, it's called a ruler".
    I bought a Vernier caliper for about 12 quid, it is an extremely useful device as it allows accurate measurements of inner and outer diameters. It takes away the guesswork when you are measuring something with a bevelled edge too.

  13. #10
    Trace where did you get the pressure relief valve?

    TIA

  14. #11
    Banned Rank = Mature Champion Trace's Avatar
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    Quote Originally Posted by dmsims View Post
    Trace where did you get the pressure relief valve?

    TIA
    It's a 12mm pneumatic push fit "flow control" valve ... freely available on e bay .... make sure you get a "flow control" and not a quarter turn ball valve ....

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