August 10, 2026 · Updated September 12, 2026

Which water valve to open when only one bed is dry

Open the valve for the bed that reads dry, and leave the rest shut. A manifold makes it easy to run every zone at once, so the habit is to open them all. Beds on one header dry at different rates. Read the soil in each bed, and open only the valves below their threshold.

Why beds on one manifold diverge

Water leaves a bed two ways. It evaporates from the surface, and roots pull it up and release it through the leaves. A shallow raised bed holds less reserve, so it empties faster than a deep ground bed. Sun exposure, mulch, and what is planted change the rate again. Two beds fed by the same header can sit days apart in how much water they hold.

In our own garden the readings show it plainly. From mid-July into early September, raised bed 1 held a band of 39% to 54%. Raised bed 3 swung further, dropping to 32% and rising to 62%. On a given night one bed can want water while the other is fine. Opening both valves overwaters the wetter bed.

What reading means it's time to water

A capacitive soil probe reports moisture as a percentage. The working trigger is 25% by default. A single low reading can be noise. Water once both of a bed's two latest readings land below that line. You can raise or lower the cutoff per bed, because the same percentage means different things in a sandy raised mix and a heavy ground bed.

A meter you carry from bed to bed gives you the same number one bed at a time. That is enough to decide a valve. A fixed probe in each bed gives you the trend without the walk. We cover the tradeoff in soil moisture meter vs bed sensor, and how to pick a per-bed number in setting a per-bed threshold.

How to water some beds and skip others

With a probe mapped to a bed, Siltwell tells you which bed is dry. When a bed logs two low readings in a row below its threshold, it fires a per-bed dry alert with a push. You know which zone to open before you touch the manifold.

Siltwell alerts you. It does not turn the valve. You still open the zones that are dry and leave the rest shut. Rain changes the whole picture at once. Siltwell holds watering across the garden when the forecast or the gauge shows real rain, roughly 5 mm or more. In our garden July brought 10.89 inches. A manifold left on a timer through that month would have drowned every bed.

Tonight, read each bed against its threshold. Open only the valves below the line. Note which beds you skipped. After a few weeks the pattern repeats. You will open the same one or two valves most nights while the deep ground beds coast.