Any ideas on how to automate this valve? This is for to fill manually my pool. I would like to simply either schedule to open or do it on the demand via HA.
Something like this connected inline with the pvc out to pool. Controlled by esp relay.
Use a magnetic Valve (like from railbird) , I use them for irrigation, works quite simple
Water solenoid valve should do the trick, using same as a sprinkler system. Usually rated for 24volts at low current. Bonus, valve will fail closed in case of power interruption. Be sure to make reliable plumbing connections, not just gardening hose clips. Pick a solenoid valve the same inside bore as the existing gate valve to maintain optimum filling times with best water flow. Switch it with a relay board or smart switch connected to a mains transformer wallwart to power the solenoid. Keep the electrical stuff inside if possible, or put it all in a waterproof enclosure, with just the two wires going out to the solenoid valve.
While you are there playing with the plumbing, why not automate your watering system as well? Another switch/relay, another solenoid, but you can use the same power supply.
A 24V irrigation-style solenoid valve is probably the simplest route if you want scheduling and Home Assistant control. They’re designed for water systems, fail closed when power is lost, and can easily be triggered through a relay or smart irrigation controller.
One thing worth considering is adding a flow sensor as well, so you can monitor how much water is being added and create automations to shut the valve off automatically if needed. That adds an extra layer of protection against overfilling.
When researching plumbing layouts for automated water lines, some of the guides from Plumber Singapore were useful to understand valve placement and water flow considerations, worth a quick visit here, if you're planning to make permanent changes to the pipework.
Also, if the existing manual valve is in good condition, many people simply leave it fully open and install the solenoid valve downstream, which tends to be easier and more reliable than trying to motorize the existing valve itself.