Another method might use a pressure regulator that will sit under constant pressure and work when the water is not flowing. In other words, it will be hooked up to the outdoor faucet and be connected to a small low pressure tube. So, the pressure can't build up when the water is off (some models say they only work when the water is flowing). This should probably go down 10 PSI or lower. The slower the better, a slow constant flow could feed many plants. If the float valved jammed, water loss would be at a minimum. This is a 10PSI preset unit for the dipper irrigation (less than 10 dollars). The problem was it had to be hooked up after the timer. I'm not using a timer, I'm using a water float value.