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Sorry, I made a stupid mistake in my calculation and Shawn is correct that the current draw is 410mA. To find out what power supply you need:
1) Either 9VDC or 12VDC should work. OpenSprinkler DC comes with a 9VDC power adapter. Although technically this is lower voltage that the required 12VDC of your pump, in many case this is OK. OpenSprinkler DC has a built-in boost converter that builds up a high voltage from the input voltage, and that’s sufficient to energize solenoids / pumps. Once energized, the solenoids / pumps typically can operate under a lower voltage. So 9VDC to operate 12VDC solenoid / valve is often just fine. If not, you can also switch to a 12VDC adapter.
2) Regarding current output: it depends on how many pumps you need to turn on at the same time. If at any point all four pumps need to turn on at the same time, you need at least 0.4 * 4 = 1.6A output current from the power adapter. So 2A should be good enough. If only one pump needs to turn on at any given time, 1A should be sufficient.