What a rain skip is, and why it matters
A controller runs the program you saved. Rain on the lot is not in that program. If nothing interrupts the circuit, the zone still opens at 6 a.m. on a wet Tuesday.
That is not a broken clock. It is a clock with no weather input. The lawn already has the inch. The extra run is runoff, a higher bill, and a soft week of turf.
How a sensor actually stops a run
Most GTA rain sensors are a hygroscopic disk under a small hood on the eave or a fence post. The disk swells when it is wet and opens a switch. That switch sits on the sensor terminals of the controller. When it opens, the valves stay shut until the disk dries.
The clock keeps going. The valve should not.
Without a skip, the zone still opens on a wet morning. With a working disk, the same start time does nothing.
Disk versus soil, and why they disagree
A disk only knows it got wet. A soil probe knows whether the root zone is still holding water. After a short shower on sandy soil, the disk may stay closed while the bank is already dry. After a long soak on clay, the disk may dry before the soil does.
No skip
The program runs through a wet week. The walk is wet at noon. The bill moves. The lawn did not ask for it.
Disk in range
A real rain swells the disks. The next start is silent. After a dry day or two, the program comes back on its own.
Wrong skip
The sensor is bypassed, stuffed with a wasp nest, or set so tight a storm never trips it. The clock still thinks it is in charge.
What you are seeing after a wet week
If the heads ran while the walk was already shining, the sensor is missing, bypassed, or dry when it should be wet. If the lawn stayed off for four dry days after one shower, the disks are holding too long or the probe is in a low, shady pocket.
This is why you do not delete the program after a storm. You ask whether the skip circuit opened.
Common problems
Rain-skip trouble is usually a wire or a disk, not a new controller.
Never wired
The hood is on the eave. The terminals on the controller still have the factory jumper. The switch cannot open.
Bypass left on
Someone flipped rain sensor to off after a dry spell and never put it back. The disk can swell all it wants.
Disks stuck or empty
Old disks crumble. A nest blocks the hood. The switch stays closed through a week of rain.
Probe in the wrong soil
A moisture probe under the downspout or in the only shade on the lot will skip a bank that is already pale.
What to look for
After a real rain, check the controller before the next dawn start.
- Is rain sensor set to active, not bypass?
- Does the display say rain delay, or did the zone still count down?
- Are the disks under the hood swollen, dry, or missing?
- Is the hood open to the sky, not under a soffit that never gets wet?
- If you have a soil probe, is it in the same sun and soil as the lawn you care about?
Customer tips
A skip is a small part. It only works if the circuit can open.
Do not pull the disks in July
If a dry week is making the skip hold too long, change the threshold. Do not leave the terminals jumped.
Test it with a cup of water
Wet the disks, wait a minute, then start a zone. If the valve still opens, the wire or the bypass is the fault.
A forecast app is not a sensor
Phones guess. A disk on this eave knows what landed on this lot.
When a soil probe is the better skip
Use a probe when short showers fool the disks, or when clay holds water long after the hood looks dry.
When to call a professional
Call when the system ran through a wet week, when the display never shows a rain delay, or when one zone stays off for days after the rest of the lot is dry.
Key takeaways
- The clock does not see rain. A skip has to open the circuit.
- A disk swells when it gets wet. A probe reads the soil.
- Bypass left on is the most common reason a wet week still watered.
- The hood has to sit in the rain, not under a dry soffit.
- If the lawn is already wet, do not add minutes. Ask why the skip did not hold.