You might benefit from a small PLC (Programmable logic controller).
If you want to stick to relays, you can't use a diode on AC, as you found out. You need some more relays. You want two things (30 s delay and 3 minute delay, I think) to turn on the solenoid valve but you don't want the 3 minute delay to reactivate the 30 s delay.
Get the 30 s delay to turn on one relay, and the 3 minute delay to turn on another relay. Put one NO (normally open) contact from each relay in parallel and get that to turn on the solenoid valve.