August 25, 2026 · Updated September 13, 2026

How to run a drip system for your garden by soil dryness

A drip system feeds water through emitters at a steady rate, evenly along every line. A timer opens the valve for a set number of minutes on set days. The timer cannot read your soil or the sky, so the runtime you set should follow how dry each bed runs and pause when rain has already soaked the ground.

What the timer measures

The timer measures nothing about the soil. A drip emitter puts out a fixed volume per hour, and the water spreads sideways and down from each dripper by capillary action. The timer counts minutes and days. It repeats the same run whether the bed is saturated or dry.

This is why one schedule struggles across a whole garden. A single valve can serve beds that dry at different rates, and the clock hands them the same water. One bed ends up soggy while another stays low.

How fast beds dry

In our own garden four beds tracked apart through summer. Raised bed 1 bottomed out at 39% moisture, while the ground bed dropped to 32% on a different day. Over the summer raised bed 3 read as low as 32% and climbed as high as 62%. A schedule tuned for the ground bed would leave raised bed 1 wetter than it needs.

Rainfall moves the target faster still. Our July brought 10.89 inches of rain, and April brought 0.54 inches. A fixed drip schedule would have run through all of July while the beds sat wet.

Zone the runtime to dryness

Set each zone's minutes from what the soil shows. Map a soil sensor to a bed and it watches the last two readings. When both fall under the bed's threshold, it fires a dry alert. The default threshold sits at 25%, and each bed can carry its own value. You learn which bed is low before the next scheduled run, then lengthen or trim that zone. This is what a soil sensor adds over a plain clock.

Longer, less frequent runs push water deep and pull roots down. Short daily runs wet only the top inch. Match the run length to how much water the bed lost since it last read full, and see our note on tubing run frequency.

Skip runs when rain covers the bed

Siltwell reads rain at the garden level and tells you to hold, that you are covered, or to water. A hold fires when about 5 mm or more is forecast over the next day or two. The covered signal turns on once at least 5 mm has landed on the bed across the past three days. On a bare timer you would run through both signals and drown the roots.

Start by watching one zone for a week before you touch the timer. Note the daily low in each bed, set that zone's minutes to bring the driest bed up to its threshold, and let the rain guidance pause the runs it does not need. From there, work through the other valves the same way, one at a time, as you learn how each set of beds dries. Our guide on a faucet timer versus beds that read dry walks the same tuning for a hose-end setup.