How to Set a Grasslin 24hr Septic Timer
Grasslin 24-hour mechanical timers are used in septic control panels to set when the pump can operate. This guide explains how to set the clock, program the white tabs around the dial, and use the three-position override switch on the illustrated style of timer.
Understand the timer controls
- Outer clock dial: Shows a full 24-hour day with hour numbers and quarter-hour marks. AM or PM appears at the 6 o'clock position for each half of the day.
- Inner clock dial: Has hour and minute hands, with the numbers 12, 9, and 6 marked.
- Index triangle: The time reference on the inner dial, near the 2 o'clock position.
- Captive trippers: The white programming tabs around the outside of the dial. Each tab controls a 15-minute interval.
- Timer override switch: Selects manual ON, Automatic, or OFF.
Step 1: Set the current time
- Identify the current time on the outer dial, checking AM and PM carefully.
- Turn the outer dial gradually clockwise until the correct time of day aligns with the index triangle on the inner dial.
- Check that the hour/minute hand shows the correct time.
Step 2: Program the pump's ON and OFF periods
Push the captive trippers to the outer ring position for the entire period when the pump is to be ON. Push them to the inner ring position for OFF periods.
Each tripper controls the pump for 15 minutes. Use the hour numbers and quarter-hour marks next to the tabs on the outer dial to identify the time each tab controls. A tab takes effect when it aligns next to the index triangle on the inner dial.
Programming example: A 30-minute ON period uses two consecutive 15-minute tabs in the outer ring position. This explains the tab intervals; use the operating schedule specified for your system.
Step 3: Choose the override switch position
To let the timer control the pump automatically, place the override switch in the middle Automatic position.
| Position | Mode | What happens |
|---|---|---|
| Top: I | Manual ON / Permanent ON | Bypasses the timer schedule. The pump is controlled solely by the float switch. |
| Middle: clock symbol | Automatic | The pump follows the programmed timer settings. |
| Bottom: 0 | OFF | The timer continues to run, but the pump will not turn on. |
Frequently asked questions
Do the white tabs go inward or outward for ON?
Push the tabs outward to the outer ring for ON. Push them inward to the inner ring for OFF.
How much time does one tab represent?
Each tab represents 15 minutes. Two consecutive tabs represent 30 minutes, and four represent one hour.
Which setting lets the timer control the pump?
The middle Automatic position, marked with a clock symbol.
Why might the pump stay off in the I position?
The pump is still controlled by the float switch. There must be enough effluent in the tank to activate the float before the pump runs.
Does the clock stop when the override switch is set to 0?
No. In the OFF position described in these instructions, the timer continues to run, but the pump will not turn on.
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