How would I go about electronically limiting the flow of a liquid (such as water) through a garden hose (or similar)? I'm building an automated system for refilling a pond since I'm sick of doing so myself. ;)

The only requirement I have is that it fails closed, i.e., it closes the valve when power is lost.

The only flow control valves I've been able to find are for large liquid volumes such as HVAC and such.

Any ideas?

Edit: It's also worth mentioning that I only need to have an "ON" and "OFF" state, I don't need variable control over the amount of liquid flowing.

  • \$\begingroup\$ search the interwebs for solenoid valves for water \$\endgroup\$ Sep 17, 2013 at 4:24
  • \$\begingroup\$ Do you need to do it electronically? A toilet float valve will do just what you ask with zero electricity. They now even make them in a form that slides on a vertical pipe, so you don't even need much space and can easily conceal it in a shroud. \$\endgroup\$
    – Theran
    Sep 17, 2013 at 4:54
  • \$\begingroup\$ @Theran, I suppose I don't need to do it electronically, but I plan to manage a lot about this pond using a BeagleBone Black. Including water level, fish feedings, sprinklers, etc. I also want to be alerted when necessary, e.g., water temperature getting too high (it gets to 110+ F here in Austin). I'm a Linux admin by trade, and I only recently got into gardening, and as you can imagine, I love to take my work home with me. \$\endgroup\$
    – Soviero
    Sep 17, 2013 at 5:31

1 Answer 1


Look for electrical, normally closed solenoid valves for water. The common and inexpensive ones are typically operated by 12 Volt DC. Several show up on an eBay search, at prices in the $6 range:

Solenoid Valve

This particular one has 0.5 inch threaded fittings.

From the BeagleBone Black, you would need a relay to switch the valve. Look for sugar-cube relays with coil voltage 3 Volts to match the BBB's operating voltage, and drive the coil activation via a MOSFET or BJT from one of the GPIO pins. Here is an example of such a relay.

  • \$\begingroup\$ This is exactly what I'm looking for, thank you for your help! \$\endgroup\$
    – Soviero
    Sep 17, 2013 at 17:57

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