I'd like to drain a water pond, with no energy input (no pump), exactly like a bell siphon would, i.e. by using a tidal flooding that empties the whole pond when it reaches its top level. But I would like to do it with a siphon pipe that is placed above the berm, and does not go through the tank wall, to avoid having to create a watertight seal through the wall. Is there any way to achieve this ?

The standard self-started siphon can be seen on this image : enter image description here I am thinking of lowering the pipe with the vent, like I drew here : enter image description here but maybe the evacuation pipe has to be lower then the top water level to be functional, hasn't it ?

  • $\begingroup$ install a valve at each side of the berm ... close both valves... use the vent hole to completely fill the pipe with water ... close the vent hole ... open both valves $\endgroup$
    – jsotola
    Jun 12, 2023 at 17:29
  • $\begingroup$ No, there is no way to achieve that with an ordinary siphon. There must be some energy source to get things started. The only one available is gravity. So water has to begin by flowing downhill. You can store energy, but you need some sort of trigger to release it, a system to replenish the stored energy, and a mechanism to use the stored energy to get the siphon started over the hump. These hydronic systems have been built in the past - usually at a big scale. $\endgroup$
    – Phil Sweet
    Jun 13, 2023 at 2:53
  • $\begingroup$ The siphon with the vent, on the first image is fully automatic and doesn't need priming. So htere has to be a solution to do the same but emptying the pond fully. $\endgroup$
    – Louis
    Jun 14, 2023 at 6:50

1 Answer 1


That vent arrangement will destroy the siphon.

any small air leak will also destroy the siphon.

We had a similar arrangement to get water out of our reservoir to supply a hydro scheme. As soon as the level got too low it would kill the siphon - hours of pumping to sort that.

I think that you would be better off using a pump controlled by a level switch arrangement. If electricity supply is an issue then perhaps a solar system.

  • $\begingroup$ Thanks but this really doesn't answer the question. The whole purpose of my question is to stay with 'passive' solutions. now source of energy. I am specifying it in the question, though I thought it was obvious. $\endgroup$
    – Louis
    Jun 12, 2023 at 11:19
  • $\begingroup$ @Louis Well, I wish you luck, I spent enough time working with the one I was involved in. $\endgroup$
    – Solar Mike
    Jun 12, 2023 at 11:49
  • $\begingroup$ thanks but the "vent" system is used on many huge ponds publicly maintained. What you are saying "the vent arrangement will destroy the siphon" is still unclear. It is really easy to creat a waterproof seal around metal or pvc pipes. The vent is here to "kill" the siphon, that is its role. $\endgroup$
    – Louis
    Jun 12, 2023 at 12:20
  • $\begingroup$ The vent will allow the siphon to work only until the water level goes below the level of the top pipe. if you want it to work, you use the vent to start and then you need to manually close it if you want to drop the water level. $\endgroup$
    – Tiger Guy
    Jun 12, 2023 at 13:02
  • 1
    $\begingroup$ "The vent is here to "kill" the siphon, that is its role". Yes, and as pictured, as soon as the water level falls below the vent intake, the vent will draw air and break the siphon. If you want the siphon to start when the water gets above a certain level, then drain down until nothing is left, you need to leave the vent off, or turn it off with a valve when you want the "pond drains completely" action to work. $\endgroup$
    – TimWescott
    Jun 12, 2023 at 20:37

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