August 13, 2026

Drip Tubing: How Often It Should Actually Run — Let the Soil, Not a Timer, Decide

Search "water tubing" and you get pages on how to lay drip line, space emitters, and clip it to a timer that runs every morning at six. Almost none of them answer the question that actually matters once the tubing is in the ground: how often should it actually run? A timer runs whether the bed is bone-dry or still soaked from Tuesday's storm. The soil doesn't care what time it is — so the run schedule shouldn't be set by a clock alone.

Why the fixed-timer default fails

A timer is a guess frozen in plastic. You set it once — say, 20 minutes every other day — based on a hot week in July, and then it keeps running that schedule through a cool, wet September when the beds haven't dried out at all. The result is the two classic drip mistakes: watering a bed that's still wet (roots sitting soggy, nutrients leaching past them) and under-watering a fast-draining bed that needed more than the timer allotted.

The deeper problem is that one timer usually feeds several beds through one set of tubing, and those beds don't dry at the same rate. A shaded bed of leafy greens holds moisture far longer than a sun-baked bed of tomatoes on the same line. A single schedule can't be right for both at once — it's either too much for the wet one or too little for the thirsty one.

Let each bed's soil set the frequency

The fix is to stop asking "what day is it?" and start asking "what is this bed actually reading?" A buried capacitive probe mapped to a bed turns that into a number you can act on. In Siltwell, a bed flags as dry — a "this bed is low" warning plus a push — only when its two most recent readings both sit below that bed's threshold. The default threshold is 25%, and you tune it per bed once you've watched how that particular soil dries out.

Two readings, not one, is the point. A single odd blip — a probe that shifted, a splash from the neighbouring emitter — won't trigger a false alarm and send you out to run tubing on a bed that's fine. And because each bed carries its own threshold, the wet shaded bed and the thirsty sun-baked bed are judged separately. In plain language: Siltwell tells you which bed is dry, so you run the tubing feeding that one and leave the still-wet bed alone.

This is the same per-bed logic that answers "which zone actually needs water" — if you're running multiple valves or manifold zones off one system, the zone-by-zone guide goes further into matching the dry alert to the valve you open.

One important honesty note: it alerts, it doesn't open valves

Be clear about what this does and doesn't do. Siltwell alerts you when a bed is dry — it does not open valves or run the pump for you. There's no relay, no automatic irrigation controller in the loop. You (or a separate timer/controller you already own) still turn the water on. What changes is that you're acting on a real dry signal from that specific bed instead of a schedule you set weeks ago and forgot.

That's a smaller claim than "smart irrigation that waters itself," and it's the true one. The value is removing the guesswork before the run, not automating the run itself.

Skip the run when rain already did the job

The other half of "how often" is knowing when not to run at all. Siltwell layers a garden-level watering hint on top of the per-bed alerts:

• Hold — 5mm or more of rain is forecast in the next day or two, so there's no point running the tubing this morning.
• Covered — 5mm or more already fell in the last three days, so the beds are topped up.
• Water — no real rain either way, so it's on you and your soil readings.

That rain signal is best when it comes from your own station's rain gauge, with the Open-Meteo forecast filling in ahead; without a station it falls back to forecast alone. One caveat worth stating plainly: this rain-skip guidance is garden-level, not per-bed. It answers "did meaningful rain hit this garden?" — the per-bed dry alert is what tells you which individual bed still needs the tubing after that.

The hardware, briefly

Per-bed sensing needs a capacitive soil probe mapped to each bed you care about. The Ecowitt WH51 is the best-value option — it reports capacitive moisture percent and pairs to any Ecowitt gateway or Wittboy console. If you run a Tempest station, note it has no soil sensor at all, so you'd add a WH51 alongside it. Siltwell supports Ecowitt, Ambient, Tempest, and Davis.

Want a sense of your spot before buying anything? The public microclimate checker compares the forecast against what nearby home stations recorded over recent nights and tells you how much cooler or warmer your area tends to run — an area indicator, not a guaranteed reading for your beds.