Folsom, California
First notes:  December 15, 2008
Updated January 14, 2009

This web page is


Notes on my experience with the SmartLine SL1600 and SLW15 Irrigation control system:

I purchased the system to conserve water and to take advantage of the rebate offered by the City of Folsom. I purchased it from who offered the best prices I could find. They were quite easy to deal with.

When I first installed the SmartLine controller, the SLW15 weather station was backordered as it was new and in high demand. I installed the controller in place of my old controller and I set up a manual program that matched my previous watering schedule.

When the SLW15 was received, I installed it and then spent time and effort to change the parameters so as to match the previous amount of water dispersed. Over time, I have recognized that was too much water. I have now adopted the default and recommended values, with the exception that I have changed the rain lockout delay, using the SLW DLY function, from 48 hours to 24 hours. I will continue to monitor the lawn and plants; perhaps as we come out of winter some modifications will be appropriate.

I changed the rain delay from 48 hours to 24 hours so as to be able to better monitor the rain sensor. Originally I had used the default rain sense setting of 1/8", and after a rain it did not clear the rain delay on its own. I then temporarily set the rain sense to 1/4", based on a recommendation from Gene Johnson at WeatherMatic (SmartLine), to see if it would actuate and clear on its own.

As the controller did not clear the rain delay, I requested and received a new SLW15 weather station under warranty. The new one seems to work as expected. I suspect the problem with the first SLW15 was a defective lithium cell that experienced a catastrophic failure that prevented the unit from notifying me of a low battery condition. At any rate, it was promptly replaced by the supplier.

I have learned that the sensor active LED, which changes from green to red to indicate that watering is shut off with either rain (1/8" in my case) or "freezing" temperatures lower than 37 degrees F, changes to orange, also indicating watering is shut off, for an additional delay period after the rain sensor dries out. However, in the case of a "freeze", the LED changes directly back to green after a day of higher temperatures without the additional delay.

The instruction book, along with the on-line references at SmartLine, do a reasonable job of explaining the system. However, there isn't an "Idiot's Guide", so my notes below will provide that functionality for me when I will have to remember all of this in the future.

Perhaps my notes may be of use to others; permission to copy and use is granted, with the understanding that the author (me) is NOT an expert in this field and that I cannot and will not be responsible for anything resulting from the use or application of my notes. My notes are not intended to replace the manual; they are intended to provide additional explanations that seem appropriate to me.

Jay O'Brien

SmartLine SL1600 Controller Settings:

Auto adjust initially does nothing until after it gets the daily temperatures from the SLW weather station at 11:50PM and runs its calculations at midnight.

Besides making the display show the correct time, this tells the controller which day of the year it is using to calculate the watering requirements. This is used, in conjunction with your latitude, by the controller to determine how much sun you receive on that day.

SmartLine says if you are using a SLW weather station (auto adjust) you should only have one scheduled run time. However, there is no down side to scheduling multiple run times; NEXT RUN times shown at midnight are divided equally across all scheduled run times. With our watering regulations in Folsom allowing automatic watering from midnight to 10AM and from 10PM to midnight on watering days, it is possible to use multiple start times to spread the watering between the morning that follows at least one not-watered day and the evening that precedes at least one not-watered day.

Zone run times are used in STANDARD MODE, not in AUTO ADJUST MODE unless the communication with the SLW weather station is interrupted. ZONE RUN TIMES are not used by AUTO ADJUST MODE to determine watering run times. Even though they are not used by the controller when it is in AUTO ADJUST MODE, at least one ZONE RUN TIME must be set for each zone to assign it to a program or programs.

Each program may have different days to water. It is possible to schedule a program that contains only drip zones to run on any day or every day of the week, as drip irrigation is permitted in Folsom on any day of the week.

It is possible to omit specific times, days or dates from watering. I haven't used this.

This is not used when the AUTO ADJUST MODE is in effect.

This entry allows the controller to determine your position on the earth between the equator and the north pole (latitude). From this the controller determines how much sun you get on any day of the year. The controller uses ZIP CODE to determine latitude.

This parameter tells the controller how much water is being distributed (precipitation rate) by the zone. The sprinkler nozzles and drip system have specified precipitation ratings; for instance, my rain bird nozzles with a water pressure of 30 psi are rated at 1.58"/hr. This parameter can be specified for each zone either in inches per hour or default sprinkler types can be selected that provide default values of precipitation per hour, as shown in a table in the manual. This parameter can be adjusted to change the amount of water distributed. If the system is set to 1.5"/hr, the default for SPRAY sprinklers, changing it to 2.0"/hr tells the controller that the sprinklers are putting out 33% more water per hour, and the controller will reduce the watering time by 33%. As an aside, unlike other parameter changes, I have found that SPRINKLER TYPE changes take immediate effect, even between midnight calculations.

This parameter modifies the watering schedule to accommodate the needs of the plant type. This is what determines the run times, and thus the amount of water distributed to a zone. The controller uses a "crop factor" that modifies the calculated (100%) base watering number that is correct for lawn mowed 4 to 6 inches tall. The "COOL TURF" selection in the controller is 80%, appropriate for our average lawn mowing height of 2-3 inches. The default values are shown in a table in the manual. The water loss to be replaced by watering is different for each plant type.

SOIL TYPE and SLOPE settings are used to break up the watering into short spurts to prevent runoff. CLAY, prevalent here, absorbs water slowly, requiring watering and soak cycles. SAND, however, allows the water to soak in almost immediately.

This is where we can adjust the watering based on localized conditions. For instance, a zone continuously in the shade requires less water.

The controller uses the day of the year and the latitude to determine the amount of sun expected (solar radiation). Every night at 11:50PM it gets the high and low temperatures of the day from the weather station; the difference between high and low temperature allows the controller to estimate the humidity and apply that to its calculations. The PLANT TYPE determines how much water is needed to replace that used by the plant plus that which evaporates. The SOIL TYPE determines how each watering cycle should be broken up, and SPRINKLER TYPE tells the controller how quickly the system distributes the water.

If watering was not scheduled for a day or days, the calculated requirements for the missed time are carried over to the next day and added to the next days calculations. This handles the one and two dry days imposed by the Folsom watering rules.

Rain and Freeze lockouts:
The weather station immediately notifies the controller when it has detected rain or freezing. Either condition prevents watering while it is present. After rain, a delay is imposed, 48 hours unless the advanced functions RAIN DLY and SLW DLY are set otherwise. During the delay, if the SENSOR button is pressed twice, it will cancel the delay. The amount of rain needed to activate the rain sensor may be set to 1/8", 1/4", or 1/2". Freeze is identified whenever the temperature is below 37F. The extra rain delay does not apply to a freeze condition.

Added clarification from SmartLine tech support:

-------- Original Message --------
Subject: RE: ET Controller notes: review request
Date: Mon, 15 Dec 2008 09:25:03 -0500
From: Johnson, Gene <>
To: Jay O'Brien <>

Hi Jay,

Thanks for your comments. Just one clarification. Regarding rain shutdown, the hygroscopic disks in the rain sensor usually dry out in 12 to 24 hours after a rain. If the rain is several inches and the weather following the rain the cool and cloudy, it might take 3 to 4 days in some cases. The SLW additional dryout period of 24 hours that you have set, commences after the disks in the rain sensor dryout. Therefore, the total down period could be 3 to 7 days. After the rain event, the controller decrements all deficits and run times to zero and it does not start to re-calculate deficits and run times until the SLW dry out period has ended. So, there could be another day at the end of the dry out before you have run times. Remember, that calculations only occur at each midnight. So, you will have run times after the first midnight after the end of the SLW dry out period.

The LED light at Sensor will be Red during the wet disk period. During the SLW dryout period, it will be yellow. During the yellow LED period, you can click the sensor button to move to Bypass which will be green. Then click the sensor again to move back to Active and the Active will go to green, ending the SLW dry out period early if you choose to do that.

Remember that the sensor LED also goes to Red when the temp is 37 degrees F or colder. It will go back to green which the temp exceeds 37 degrees. Any start time during the freeze period will be lost, so if you have cold temps early in the morning, it is best to have your watering start time later in the day.

H. Gene Johnson
Tech Support

3301 W Kingsley Rd
Garland, TX 75041
tel: 972.278-6131
fax: 972.271.5710

SmartLine controller and Weather Station:
City of Folsom Water Conservation:
City of Folsom iConserve:
Irrigation Water Needs of Landscape Plantings:
California Irrigation Management Irrigation System (CIMAS)