Moisture estimates not close to reality, what to do?

I happened to have one of those moisture meters you insert into the dirt to get a reading, and I tried it yesterday on several spots on the lawn. The reading was either pegged as far as it could go, or at a minimum it was around 8/10.

The system watered for a total of an hour with 10 minute soaks two days before. After that this put the zone moisture reading to 86%. Two days later is when I took the reading and the system said it was 36% and now today it’s saying 15% and it wants to water tomorrow.

What? The dirt is soaked 7 inches down! This is clay and appears to hold water very well.

The system is set up for flat, lots of sun, clay, and “rotary”.

I have compared water bills since I installed the system in June of 18 and I’ve really not seen any savings in usage. In fact, the last two June-July billing cycles have shown about 100 GPD more than the old system which was on a fixed timer. The lawn looked fine on the fixed timer, and it ran like 15 minutes every other day.

Thoughts? Just go back to manual schedule?

A manual fixed schedule can be good if you know it works – you can still get smarts with rain skip if set that way (just be sure to use a good known weather station if one is near you).

If you want to continue with a Flex schedule, I suggest taking a look at the advanced zone settings. The easiest variable to tweak would be root depth – you may need to go shallower. Shallow root depth setting will mainly reduce the watering time (and I believe will increase watering frequency). The other easy setting to tweak is the crop evapotranspiration – you may need to lower it 5-10% to better represent your lawn’s use of water and resultant soil moisture. Reducing the crop evapotranspiration will decrease the watering frequency. When you tweak one value, apply the changes, then take a look at the soil moisture graph and table to see how that changes future waterings.

Thanks for the input!

I guess I don’t follow why trying to “fool” the system into thinking things are not what they really are is better than just doing a fixed schedule?

It’s not fooling, but tuning. The defaults are assumptions that need to be checked (such as nozzle in/hr, Root Depth) or researched (soil Available Water, crop Evapotranspiration) to then tune the advanced zone settings for peak watering efficiency. Flex Daily will save alot of water compared to most fixed schedules as Flex tracks water balance from rain and irrigation, along with use of water by plants (Evapotranspiration). Flex should also result in more resilient plants by encouraging deeper roots and, ideally, watering exactly when needed. However you need to spend a bit of time tuning to maximize benefits. If your fixed schedule seemed to work well, and you do not wish to spend time tuning Flex, no harm in going back to a fixed schedule. However it won’t have any advanced soil moisture tracking.


The house is in an region that basically won’t see any rain from now until late October, maybe November. And the weather is incredibly consistent. 80s and even 100s for June/July/August.

I’m wondering if I can just use the moisture meter to figure out how quick it dries out and then set it to fixed schedule. And rain skip on in case of some odd ball rain.

I don’t understand what the advanced fields are even though I’ve tried reading the help file. My eyes just kind of glaze over. lol

I just can’t understand what settings would stop the system from thinking the lawn is at 0% after 3 days since it was watered.

As was mentioned above, If the system shows the water having evaporated faster than reality, then you need to adjust some of the advanced Parameters like The Crop Coefficient (Evapo transpiration). By lowering that value, you are telling the system the water does not evaporate as fast so watering will be delayed longer.
Once you make a small change to that value, you check the schedule again and see if it better matches what you believe is the reality.
This tuning is necessary, as Soil and evaporation cannot be summarize into 7 soil types. Once the tuning is done, then you will be able to forget about the system and let it run its course.

If you don’t have the patience to do the tuning, then you can just use fixed schedule, and just get the benefit of Rain Skip (which is of little use in your region from what you said). But it considerably reduces the benefit of buying a Rachio…

That is up to you :slight_smile:

I had thought that “allowed depletion” was the best way to reduce watering. No? I set it to 65% on the front lawn and the moisture level remained and it keeps wanting to water.

Should I just set it back to 50% and then try the CC setting instead?

There are only two watering parameters in the end, Duration and Frequency.
So several parameters will affect each of these probably in subtle different ways unknown to us

Parameters that would increase Time between watering (less frequent):

  • Lowering allowed depletion (Tells the system to wait for more evaporation to take place before watering).
  • Lowering the Crop Coefficient (Tells the system evaporation is slower so watering can be less frequent)

So you can try lowering the AD further, and if it requires a too extreme value, you can try combining it with a lowering of the Crop Coefficient.

Just make sure that before you change a parameter, you go in Soil moisture > More details, and write down the current moisture balance % for the days ahead.
Then, that you change only one parameter at a time and go back to Soil moisture > More details, and write down the new moisture balance % for the days ahead to see how much of a difference it made.

If the Moisture balance rises, then it means the system calculated the water will last longer and therefore watering will be less frequent.

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