Aeration - Trying to get the most from siphon outlet - Part 2

Part 1 : Here

Part 3 : Here
Part 4 : Here

Made few more aerator and testing it..

The first one, the one that I copied aquarium pump method. I use "T" join but with a smaller junction of 15mm and 25mm main pipe, I need the 15 mm part of the "T" for the aerator "tongue" and see photo below how its made.
Cut diagonally a 15mm pipe and make a slit as shown, the slit is to enable the 15mm pipe to be inserted all the way in the "T" as photo below showing the Trailing Edge tongue.
The aerator use 25mm pipe and attached it after the double elbow and photo below show it aerating during a flush cycle. Its make less noise if compare to the one with many holes down tube.

Not bad, aeration is okay but then I need to make another different and probably simpler.

This time I use 25mm ~ 50mm reducer to make use of 50mm pipe as an oversize down tube, as photo below.
I drilled 3 holes on the reducer slanting surface to facilitate aeration. Without this hole aeration will be at minimum and flush will not start.
Completed aerator is attached after double elbow and photo below show it in action. Aeration good and its almost silent.

Not satisfied with above I make another variation with a venturi, hoping to get that extra boost of aeration. Photo below is a derivative of above with  additional two 25 ~ 50 mm  reducer arranged to make a venturi pump.
The venturi pump part (the waist) suppose to provide extra suction drawing more air into the mixing. The 3 holes on the top reducer is still same no change and its mounted at same location.

Photo above shows it in action, its very difficult to see which is better between these two. But the one without the extra reducer is cheaper and easier to make. Noise level is same, almost silent.

I left the one with the venturi pump on my growbed since that the one last made. On my installation I need the double elbow since the water drop is not deep enough to do the effective siphoning cut-off with these 3 setup.

If you have the height and put a slight restrictor before the aerator it should work without double elbow.

Between all 3 above I like the second unit since its the easiest to make, but the last made with the extra reducer, its shows giving extra aeration. No figure to support above test purely base on visual comparison.

Noise level has been reduce tremendously by all three design and I'll stick to using above designs for my siphon outlets.



  1. What is the thought in the length of downward part of the siphon outlet? Did you test to see if there is a difference between having the outlet end just below the water level and then having the outlet end just above the bottom of the growbed, in terms of sound and aeration? A potential issue with having the outlet end just below the water level is fish swimming up in the outlet and then getting blasted when the siphon kicks, but I don't think it would kill them.

  2. @bigdaddy0301, if the outlet just below water surface, siphon works but aeration is very little, this may cause problem to fish.

    If outlet is just below growbed, it may fail to stop siphon due a minimum of about 6 inches is required below growbed to ensure reliable siphon operation.

    I have design a new siphon outlet, this eliminate problem of siphon outlet aeration is its very near to water surface.

    You can check at

    for the modification done and ensure noise and aeration taken care off.


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