Solenoid valve control

I have installed a Rainbird solenoid valve in my garden. It is switched via a Fibaro double relay with 24vac and the relay is powered with 220vac. I use a button from virtual devices to switch it on and off. It works great.
Questions: (not sure if this should be separated topics as they kind of intertwine within same project)

  1. the solenoid makes a buzzing sound when turned on. I don’t really hear it because it is softer than the noise from the nearby pomp and the sprinkler. When the solenoid is connected directly to the transformer it made it only a click once when switched. Is that anything to worry about? Could it be that the combination of hard core wire and the relay leak power? The transformer is 0.8 ampere only, but is the official Rainbird brand. I want to add one more solenoid, powered and controlled by the same relay and thus transformator. I have another one of 2.0 ampere. Will that be better or can I risk to burn the solenoids?
  2. The second solenoid is opening closing flow to my neighbour. We share the pomp and well. We do not use it at the same time. They do not have any domotica. My mesh is good where they want to switch the pomp. What is the best way for them to switch via my domotica without Risk of technical challenges and full access to my system?
  3. What is the best way to make ad hoc rotations on multiple solenoid valves? I.e. valve 1 on for 2 hours, the closes and valve 2 opens for 3 hours etc.?
  1. shouldnt be a problem. If you use stronger transformer, it wont burn your valves. Valves will use only so much power as needed. Voltage is important - cant be higher.
  2. Just provide to your neighbor some remote button (zigbee or zwave) to start/stop the pump.
  3. It depends on your preference. You can have separate flows for On and OFF, you can use timers and you can also use inbuilt feature of relays (auto off after specified time parameter) which Im using as a security feature in case central unit goes off and valves remain open = water would be running for hours. So in my case, watering of garden takes 5 minutes (single flow with ON and 5min delay OFF) and in relay itself there is 10min auto off setup. So the longest time in case something goes wrong is 10 minutes managed by module itself.

Thanks Igy,
That is a good sanity check on exactly what I had in mind. We are sprinkling up to 12 hours. Valve sequence and duration will be dynamics, so I hope to find a way to deal with that. I suppose I will have to work with some flows to select from and default timers. When I have more experience to evaluate I will look into it again. I realize I may need to check if there is an open valve without hose connected. Maybe a flow or pressure meter. That is next level.

I am now adding 5 solenoid valves. Each controlled by a fibaro relay. I will use a panel to switch zones on and off. The idea is that each activated zone will be active for i.e. one hour and then the next active zone will start. I can make flows that start and stop each zone in a loop. However, I want to use only activated zones and not always all zones. Does anybody have any idea how I could do that?