What size (gallons per hour) pump
 

Ron, What size (how many gallons per hour) pump do you use in the 11 plant garden that is made with 1" pipe?

What size (how many gallons per hour) pump would you use for a garden twice that size?

How do you figure gallons per hour for any size garden?

You can use a small pump like a 60 GPH without a flow control. So you can use almost any larger size if you use a flow control valve to slow or redirect some of the water back to your tank. So if you add more units you just open up the valve to accommodate more units. That's why it is a good idea to always buy a larger pump because from experience you will want to expand when you catch the hydroponics bug.

You could probably fill 3 11 plant gardens with a 120 GPH pump if they were right above the tank. It would just take longer to fill more units which could be an advantage if your timer only has 30 minutes on/off pins.

If a pump won't fill a certain garden or take to long to fill then I know I need a larger size. If water starts to come out of the little hole in the over flow pipe then the pump is to large for the system. So I can either add a flow control valve to slow down the water to the garden or I could add another over flow pipe somewhere in the garden to handle the increase in water volume.