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I have assembled a small DIY drip-irrigation system for my terrace garden. Please have a look at the attached image. I switch on a small pump to start the drip-irrigation system and then switch it off. But even after that, the water keeps flowing through the system and stops only when I physically lift the pump out of water.

How can I stop this water flow without requiring any physical action?

Please note that I plan to automate the switch-on/off of the pump using a timer so that it functions without requiring my physical presence.

Drip Irrigation System Setup

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I tried the suggestion of "Making a pinhole in the highest point of the pipe." It worked like a charm and solved the issue I was facing. Completely loved it, more so, because it does not involve procuring new stuff.

I also like the option of using a solenoid-valve, but have not tried it yet. Will use it when I install such a system again where the tank is at a considerably higher place than the plants.

Thank you everyone who took the effort to write an answer, and that too with detailed explanations.

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  • $\begingroup$ I tried the two tank option but when using 1|4 inch tubing i found that an air lock developed, even if i kept the far end of the water delivery pipe open but above the level of the second tank,in the delivery tube to the drippers. I just couldn't get it to start to drip again , without manual intervention, once air got into the pipe. This prevented it being a solution to the holiday watering problem. Still looking for a solution, may try a direct pumping with syphon break by air admittance solution. $\endgroup$
    – nick
    Jul 21, 2017 at 18:06
  • $\begingroup$ For another system, I like the method of the pot base permanently immerged in 1/4 inch of water, and a bottle with the top down which only lets air in and water out when the 1/4 inch of water goes empties, when air reaches the hole at the bottom of the bottle, it enters the bottle and water falls out... $\endgroup$
    – bandybabboon
    Feb 9, 2019 at 11:31

11 Answers 11

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You want to let air into the pipe when you switch the pump off, without letting water out. Here's a few ways to do this.

  1. Make a pinhole in the highest point of the pipe. You will lose a bit of water this way, but if it is above the tank, the water will drip back in (provided it doesn't spray too far.) You could even put it just under the tank lid.

  2. Install a tee and riser at the highest point of the pipe. this will need to be high enough to avoid the pump pressure pumping water out of the riser.

  3. Install a vacuum breaker valve. This is basically a non-return valve, letting air into the pipe but not letting water out.

  4. direct the outlet of the pump to a high point via a short tube. Collect the water in a funnel and feed the water from the funnel to your plants. Funnels can be made from the top of plastic bottles, cut off and inverted (you may have problems with thread compatability though.)

Knowing the backpressure in the line will help make the best selection, especially for options 2 and 4. I assume that for good distribution to your various plants, you have restrictions at the various outlets.

For option 1 (the cheapest option here) your pinhole should be similar in size to one of the plant outlets. This should avoid wasting too much water, while allowing the incoming air to break the syphon (if it is too small and/or the flow of water is fast, the current may be strong enough to carry all the air bubbles away. A wider pipe section at the high point will help avoid this.)

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  • $\begingroup$ I like number 4 the best, as it doesn't require extra valves or 'tees' . $\endgroup$
    – Carl Witthoft
    Apr 28, 2016 at 11:48
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    $\begingroup$ @CarlWitthoft it depends. If the nozzles at the plants is restricted, the pressure may be insufficient with 4. On the other hand, the more restricted the nozzles are, the better 1 should work, as the air coming in from the pinhole won't be carried away by the insignificant water current once the motor is turned off. $\endgroup$
    – Level River St
    Apr 28, 2016 at 12:10
  • $\begingroup$ I loved option (1). It worked like a charm. Infact, I had thought about this earlier, but then had doubts whether it will actually work. +1 for explaining in detail about option (1) $\endgroup$
    – javed
    May 4, 2016 at 14:46
  • $\begingroup$ +1 for option (1) $\endgroup$
    – Theofanis Pantelides
    Jun 22, 2018 at 21:09
  • $\begingroup$ We had some extra piping and some spare tees, so Option 2 was a good one for us. By going vertically upwards from the highest point on the system, we went just under 1.5 times the height from the pump to the highest point of the system, and this was adequate to prevent overflow during pumping but preventing the siphoning once the pump shut off. Thank you for the question and answer! $\endgroup$
    – Chris Alexander
    Aug 24, 2021 at 13:10
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There are two ways to stop a siphon:

  • Put a valve inline with the siphon that simply blocks the flow, "freezing" the state of the system. Flow will resume as soon as the valve is opened again, without needing the pump to re-prime the siphon.

  • Put a valve in the top of the siphon that allows air into the tubing, breaking the suction that keeps the siphon flowing. Close the valve and operate the pump to restart the flow.

For the second option, you can get an automatic valve, known as a "siphon breaker valve" or "antisiphon valve" that admits air into the system as soon as the pressure in the tubing drops below atmospheric pressure.

Of course, a third option is to rearrange things so that you don't create a siphon in the first place.

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  • $\begingroup$ I like the proposal for an air gap. That's a fantastically simple idea which requires absolutely no action other than initial installation. $\endgroup$
    – do-the-thing-please
    Apr 27, 2016 at 18:26
  • $\begingroup$ Depending its placement and the pump being used, a check valve may allow the system to enter a state where the pump is ineffective. If the check valve is just above the pump, for example, and the reservoir gets pumped dry but is subsequently refilled, the pump and the pipe connecting it with the check valve may get filled with air. A centrifugal pump can produce a tiny bit of pressure when filled with air, but not much. If getting the air through the check valve would require more pressure than the pump can produce, the pump will be unable to do anything. $\endgroup$
    – supercat
    Apr 27, 2016 at 21:39
  • $\begingroup$ @supercat: Nobody suggested a check valve. $\endgroup$
    – Dave Tweed
    Apr 27, 2016 at 22:29
  • $\begingroup$ @DaveTweed: Sorry--I mistook the first described option as a check valve rather than something like a solenoid-operated valve. Though that does bring up an interesting notion: if one maintains a siphon from the tank to a point below the water level in the tank, one could simply use a solenoid valve to let water flow, rather than having to use a pump. $\endgroup$
    – supercat
    Apr 28, 2016 at 14:27
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    $\begingroup$ @supercat: Yes. Also, your point is valid in the sense that if the OP were using a positive-displacement pump (with two check valves internally) instead of a centrifugal pump, he probably wouldn't have the siphon problem to begin with. $\endgroup$
    – Dave Tweed
    Apr 28, 2016 at 14:55
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An alternative answer which requires no physical action in the system is to move the tank or the garden so that the full water line level is below the level of all of the outlets. You may have to scale up your pump for the additional head required to lift the water. I am also assuming the outlets aren't submerged within the garden after irrigation, since then you'd be flooding your garden. If this is the case, then you'll have to move the tank lower.

Obviously, this requires an initial physical action to set up the system this way.

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How can I stop this water flow without requiring any physical action?

You could add in a solenoid valve downstream of your pump that switches off when the pump shuts off. These can be found for a reasonable price online. You should be able to wire it to the same switch as the motor and once de-energized, it will close itself.

solenoid

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1) If you have a siphon system, why use a pump? Use a valve to turn the siphon flow on/off. Much cheaper than running a 40W pump. A simple gate valve at the crest will work perfectly in conjunction with a foot check valve at the inlet and another check valve at the outlet to prevent reverse movement of air into the siphon when it is shut off leaving the siphon primed.

2) If your going to use a pump, make the pump do the work. Rearrange your system to get rid of the pipe sloping down, so all the piping slopes up

3) A 1 psi check valve at the outlet of the pump should break open when the pump starts, and close even under the siphon suction.

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If your pump lifts the water into a hopper, from which it flows under gravity to the plants, this will provide the air gap mentioned in some of the other answers. The hopper could basically be a funnel pushed into the end of the hosepipe. It should be sized and positioned (height) so that it doesn't overflow too much, and over the top of the water container so that any overflow falls back in. This could be quite an easy retrofit depending on how your system is set up already.

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  • $\begingroup$ This is idea #4 in LevelRiverSt's answer, btw. $\endgroup$
    – Carl Witthoft
    Apr 28, 2016 at 11:49
  • $\begingroup$ @CarlWitthoft You're right, don't know how I missed that. There are still a few bits that seem like useful additions here, but probably should have been a comment $\endgroup$
    – Chris H
    Apr 28, 2016 at 14:12
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How about using two water tanks. Pump sits in tank 1 and pumps twice a day for 5 minutes into tank 2. Tank 2 has the siphon connected and waters the plants via drip irrigation as before. The drip irrigation will only drip as much water as the pump pushes from tank 1 to tank 2 in the five minute interval. The siphon part can remain 'charged' as the water level in tank 2 reaches the water level at plant height.

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  • $\begingroup$ Hi JRN, welcome to Engineering SE. This solution would work but it seems over-complicated for the task. $\endgroup$
    – Air
    Apr 28, 2016 at 18:16
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The best way to stop the flow of a siphon is to have a shutoff valve inline at the crest. The valve can have a mechanical timer. This will work if an anti backflow foot valve is inline at the inlet and another check valve is inline at the outlet to allow flow in one direction while preventing air from entering and migrating up the long leg. This allows complete control of the siphon and when it is shutoff before air is allowed to enter the line, it stays primed for further use. US Patent 5,358,000 was the first to teach this method of siphon control.

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  • $\begingroup$ I might add that a siphon can be used to automatically drain standing water in areas prone to pooling. $\endgroup$
    – Michael T
    Mar 4, 2019 at 16:53
  • $\begingroup$ To use a siphon for removal of standing water, first fill the hose with water and position the inlet into the lowest pocket of the area to be drained and add a weight to keep it fixed at that elevation. Lower the outlet of the siphon and start the flow allowing the water to be drained to a point just above the siphon inlet, leaving a small amount to prevent air from entering the hose. Fix the outlet at this elevation and the siphon will automatically empty the standing water to this point as long as the inlet does not get clogged or allowed to get air. $\endgroup$
    – Michael T
    Mar 4, 2019 at 17:02
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I was looking at this site to try and figure out how a syphon might break other than by an air leak. However I might like to make a suggestion! I use a siphons to do a trickle water drain from my aquarium. In my refugium we have a toilet type bulb float that kicks on when the water gets too low. On the other side of the refugium I have 2 wells (one inside the tank and one outside the tank) with a syphon between them... the well on the inside of the tank has holes in it so water from the refugium can flow into it. They are at the lowest level I want the water in the refugium to reach. Outside the tank I have a well that has one drain hole with a tube inserted that is lower than the lowest water level in the refugium. I hope you are following this ok. What happens is water trickles out of the refugium into the inside well. The syphon carries water to the outside well (which never runs dry). The outside well drains water to the drain but only can do it until water reaches the level of the water of the hole in the outside well. I have a shut off valve in the final drain to be able to stop the whole process! My issue has been somehow the syphon gets broken from the turn off valve to the drain. But I think I have solved that issue by reading this! I can send pictures if it will help! There are no pumps involved at all! Only gravity and strategic placements!

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    $\begingroup$ Welcome to E.SE. A diagram would save a lot of words and, hopefully, explain it much better. Use 2 x <Enter> for paragraph breaks to break up your wall of text. $\endgroup$
    – Transistor
    Feb 8, 2020 at 18:14
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enter image description here

I just used an anti siphon valve from my aquarium air stone kit. Worked like a charm!

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Bell syphon (or modified version). https://www.youtube.com/watch?v=lyrvcCqv5V0

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    $\begingroup$ Please don't post link-only answers. Add any detail that is needed into your answer so that everyone can be helped without going somewhere else on the internet. $\endgroup$
    – hazzey ♦
    Nov 14, 2020 at 2:03
  • $\begingroup$ Some elaboration might be helpful $\endgroup$
    – Mahendra Gunawardena
    Nov 15, 2020 at 12:49

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