I am looking to attach two 1" valves to a drainage line I have coming from my gutter. I would like the option to select which channel the rainwater flows down, using valves. My hurdle right now is finding the right type of valve, as the ones i have seen require a minimum pressure, whereas i will have little to none (all pressure from gravity) It seems like a gate valve would be the right option for this. How can I control the water automatically and with a valve that does not require water pressure to activate?
Do you really need "valves" to control rain water? Assuming your two destinations are a barrel and the street, all you really need is a flap.
Use tin snips to create a branch in your down spout, create a makeshift hinge using a stainless steel rod, and put a plastic flap on it. Make the flap out of any piece of plastic.
Look DWV flaps. PVC fittings in various sizes with hinged flaps on one end. Maybe you could adapt one.
Then all you need is an actuator for the flap. Look up "actuator" on Amazon ... there are all kinds of them under $50. At first glance, an easy one would be a 12V automotive one meant for diverting to face/foot vents in a car.
This will all look a bit makeshift, but I suppose that's in keeping with what you're doing? And anything professional, like "flow diverters" for agriculture or commercial HVAC, will cost hundreds or thousands of dollars.
You can use a valve that's intended for use as a heating system's zone valve. These are electrically operated and take less than a minute to open fully. They generally operate at 24V AC. They require no water pressure at all to operate.
You can get a straight-through model or a 3-way model that has one opening for "IN" and two openings for "OUT". The motor selects which opening is "OUT". These are just a little more expensive than straight-through models.
Look at the specifications for the valve, and if you want better flow, buy one that has a higher Cv rating. This is the valve's "flow coefficient". The higher the number, the better the flow. Numerically, the number is gallons per minute at a 1 psi pressure drop.
Example below, photo credit supplyhouse.com (I have no connection with them.) NOTE: These are not intended for use outdoors without an enclosure, as they are not weather resistant.
Think about setting it up as two zones on a sprinkler system with two "on/off" valves hooked up to your drain line. You can get the valves at any home store and they are pretty cheap and require no pressure to operate. See picture below from Home Depot. https://www.homedepot.com/p/Orbit-1-in-FPT-Auto-Inline-Valve-57281/300642255#overlay
You can use a controller/timer to operate the valves. It supplies the 24 volts required to operate the valves. See photo from Home Depot. https://www.homedepot.com/p/Orbit-4-Zone-Indoor-Easy-Dial-Timer-57594/300642245
You could either use a straight wired Solenoid valve such as this one: https://www.amazon.com/gp/product/B06XWGF3CX
Or if you want something automated you could use this Valve Controller: https://www.amazon.com/Compatible-Assistant-Application-program-Android/dp/B09L5PB6B7
This one sits on top of an existing Ball Valve and closes or opens the valve depending on the command given.
Note that NEITHER of these are NO (Normally Open) or NC (Normally Closed). In other words, once de-energized they will stay where there are. They use less power since they are only energized when turned on or turned off.
If for example, you want to make sure that the valve is Closed if the power is out or once the requested operation is completed then you will want to look for a NC (Normally Closed) type of valve that will only stay Open as long as it continues to receive a signal.
This could be called rain capture system with fully controlled rain water capturing and distribution system with remote control.
First you will need is Downspout Rain Water Collection Diverter Connector- they come in all forms and shapes.
Then you need 1 or 2 inch hose to feed the barrels. Here you can expand (in the future) to electricity controlled valve to stop the barrel fill, or to redirect directly to plants. For that you can use an inline sprinkler system valves that are already build to work in wet environment
Barrels you can get cheap ($10) at the barrel recycling centers (look for one), just pay attention what was in it before).
Connect multiple barrels (depending how much you want to capture and how much you consume) in parallel at lowest point of barrel and set barrel on bricks to get some elevation for the flow.