I would water only as long as it took to fill your garden. Then let it drain and when all the water is drained from the garden then water again in another 30 minutes.
Running the
pump longer than it takes to wets the roots serves the plants no benefit. It is very important to under stand that when the garden water rises it not only is watering the roots but also is pushing spent oxygen out the top of your medium and when the water drains fresh air is sucked into the medium.
The more times this action happens the healthier your plants will grow.