August 17, 2026 · Updated September 12, 2026

How much water a garden needs before water well drilling

A garden's water demand is much smaller than the sum of every bed watered every day, because rain refills the soil and the soil holds water between waterings. Before you spend on a well, measure how often your beds run dry. In our own garden most beds went for weeks without dropping near their dry threshold.

How a garden spends water

Plants pull water out of the soil through their roots, and sun and wind drive it back into the air. That loss is your demand. Rain refills the soil, and the soil stores what it holds until the plants draw it down. A well only has to cover the gap between what the plants use and what the sky delivers.

That gap swings with the weather. A wet month leaves almost nothing to pump. Across July our garden caught 10.89 inches of rain, and August added another 6.56 inches. Through stretches like that a bed can sit at the top of its moisture range for days.

Rain also arrives in bursts. Our wettest day dropped 2.46 inches. One storm like that refills a bed and covers it for the better part of a week. Siltwell's watering guidance works across the whole garden. It holds off when at least 5 mm of rain is forecast within a day or two, and it marks a garden covered once at least 5 mm has fallen over the last three days.

What our beds drew down

A soil probe reports moisture as a percentage of capacity. When it stays high, the plants aren't thirsty. From mid-July to early September our beds held steady.

• Raised bed 1. Ran 39% to 54% across the window.
• Raised bed 2. Ran 36% to 57%.
• Raised bed 3. Ran 32% to 62%.
• Ground bed. Ran 32% to 62%.

A bed's default dry threshold sits at 25% moisture. None of our beds touched it across those two months. On the demand a well would have to meet, that window asked for very little added water. You can set a per-bed number that fits your soil with our baseline threshold guide.

Each probe tracks a single point inside one bed. It cannot tell you the flow rate a driller will hit in your ground. It sizes your demand, and it says nothing about the aquifer below you.

How to size demand before you drill

Track what your garden draws for a full season, then match a well to that gap instead of to every bed watered daily. Three steps get you a real number.

• Probe your driest bed. Put a sensor in the bed that catches the most sun and wind, since it dries first. Read it against your per-bed moisture.
• Log the rain. Record what falls each week and watch how long a soaking holds a bed above its threshold.
• Count the dry days. When a mapped sensor's two most recent readings both fall below its bed's threshold, it fires a dry warning. That tells you which bed is dry and which to skip.

Once you know how many days each bed needs water and how much a run delivers, you have your gap. Feed a pump from that number rather than from the whole garden at once, with our guide on running a pump only when beds are dry. A drip line can then run only where the soil reads dry.

Log one full season of rain and per-bed moisture before you call a driller. If your beds hold the way ours did, you may find a rain barrel or a storage tank covers the gap and postpones the drilling bill entirely.