enter image description hereI've set this up for my hydroponics water distribution system. The water is pumped up, and is distributed via the valves. I can manual control the valves so that each outlet has a steady flow of water.

However, the pump is on a timer and when it turns off and back on. The flow isn't even. Certain sections have water flowing through them, while some have none.

I'm thinking adding a check valve that would prevent backflow when the pump is off. Will this ensure steady flow to all the outlets? What causes the uneven distribution?


  • $\begingroup$ check valve will prevent backwards flow, won't necessarily make it easier to balance. Take into consideration height differences, length and diameter of tubing, nozzle sizes .... don't know I'd this helps you, but it's like an electrical network and each one of those things is (very loosely) like a resistor, except height differences, which just adds a pressure difference $\endgroup$ – Pete W Mar 25 at 0:10
  • $\begingroup$ Thanks for the reply. If thinking like a electrical network then I should add more powerful pump to increase the flow. But I'm not sure if that would solve the siphon problem. $\endgroup$ – Methos Mar 25 at 0:54
  • $\begingroup$ Looking at the picture, and assuming outlets are at the same height, I'd say either make each 1/2" section significantly more restrictive, or try to accomplish the same thing with the valves by keeping them all just-barely-open. Your pump may need to be more powerful in pressure (head), not necessarily flow. At moderate flows, pipe pressure drop scales with Length/Diameter^4. You want the individual branches to contribute lets say 80%+ of the pressure drop, compared to the 3/4" main line. Then it will be roughly in balance, and the outlet valves could be used to trim it. $\endgroup$ – Pete W Mar 25 at 2:21
  • $\begingroup$ Thanks Pete! The 1/2" outlets are same height. Vertical line is 7ft, and horizontal is 5 ft. Also in the drawing I only have 10, but the actually system has 20 outlets. With a 700 gph pump. Definitely seeing a pressure drop, especially with so many outlets. I have a spare 900 gph pump, maybe that will help? $\endgroup$ – Methos Mar 25 at 3:17
  • $\begingroup$ does it have to be a pressurized system, or would an open channel work? What kind of backpressure is there at the outlets? $\endgroup$ – mart Mar 25 at 7:27

One basic way is to adjust the valves, the dry ones fully open and the ones bleeding all the pressure just slightly open, or even restricted permanently by a smaller size bushing just before the valve.

In conjunction with that, you can install a water tank between the pump and your network with an adequate head and a hydraulic actuator to stop the tank's drain till it's full.

Finally, you may need to change your pump to one with more GPM. You want to start from the easiest choice and move on to the next.


The most precise way to control flow is with valves/flow regulator. The main problem is the cost. Although, its a very basic component and its not too costly if you have too many outlets the cost will pile up.

Hydroponic water flow regulator

Even if you had matching orifices, you might have issues with the pressure drop inside the pipes and corners.

Another way to control the flow would be to restrict the flow (e.g. reduce the size of the orifices). That way if you have sufficient flow, you will have a pressure increase in the network and the pressure will be the key factor diving the flow. In that case though, you'd best change the topology of your network into something like

enter image description here

The topology presented above will have similar running lengths to all orifices, and the same number of turns. However as you may already understand this is not optimal, since a) what you save in flow regulators you will probably be less on the losses you incur from the added lengths and t junctions and the added installation costs (more labor costs for cutting and joining) and also b) from the added lengths and T junctions the network will suffer greater pressure drops and also there will be more points with potential leaks.


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