I am designing a small automatic drip irrigation system. There will be about 10-15 drippers. Flow through the system will be about 1 l/minute, but this may change if expanding or reducing the system. The entire dripping irrigation system expects a pressure of around 1 Bar (precision is not needed). I only have a water reservoir and I planned to use a submersible pump (ideally a quiet one) to pressurize the fluid system.

This seems to be harder than I expected because all the pumps I see are designed for completely different conditions - especially much large flow - e.g. 15 l/minute. If there is one with a lower throughput, then it also has a smaller pressure than I need. It looks like moving a small amount of water at a higher pressure is harder than a larger amount.

Some ideas:

  1. Can a water pump e.g. 12V, 1.5 Bar, 15 l/minute be used with a lower voltage to achieve 1.5 bar and 1/l minute? Could this be combined with pressure sensor and PID regulator?
  2. What about some water returning back to the reservoir to keep the water flow at 15 l/minute. Could a pressure valve returning water back to the reservoir be used for this?
  • $\begingroup$ Get pump curves for the options you have, showing flow vs pressure. Then increase pressure drop (eg with small tube or orifice or needle valve) to obtain approximately the flow you need. 15:1 turndown might be hard to keep consistent with cheap pump, maybe doesn't matter. For 1bar, you could maybe construct a water tower (bucket in a tree, 10m height) to give very repeatable pressure. If you can design a system that works at 0.2bar, you only need 2m elevation, any pump will do, quite easy. $\endgroup$
    – Pete W
    May 11 at 14:45
  • 1
    $\begingroup$ also, if you can't find the right pump, but you can find only larger flow ones, you could try a small bypass system with a flow regulator and a check valve that returns the excess water to the inlet. At the end of the day it might be a lot cheaper to buy and install. $\endgroup$
    – NMech
    May 11 at 16:06
  • $\begingroup$ If the watering stations are all located at equal elevation... 1-Bar is about the pressure of 30-feet of water. Have a raised reservoir of water with a float valve (like a toilet tank float valve). When the water level drops the valve allows water to be added. If you can minimize the transport losses (with PVC pipe not fine tubing), the gravity head will provide the pressure at the emitters. $\endgroup$
    – Jim Clark
    May 16 at 14:49
  • $\begingroup$ Thank you for your suggestions. The whole setup will be placed on a balcony, so using higher altitude is not viable. I am thinking of using something like this ebay.co.uk/itm/163934982602 combined with maybe some ball valve to create bypass flow back to the reservoir. This could be combined with pressure indicator, maybe like this eshop.agf-zavlahy.cz/Souprava-na-mereni-tlaku-vody-d7.htm Another idea is to use also electric water pressure sensor to regulate the pump power in order to compensate smaller changes in the system. What do you think? $\endgroup$ May 19 at 9:30

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