Percolation Rate Information

TLDR (Too long didnt read): Typically if you fill the planting pit up with 6” of water, it should take 10-60 min for 1” of water to drain. If it takes longer than 60 min for 1” to drain you should impliment a extended sump detail or a french drain detail


The standing water and percolation all help the user form an understanding so that they can better adjust their watering volume, application rate and frequency optimally for the tree. Ideally the watering volume is as high as possible without the sump indicator ever rising, while still giving the soil time to breathe between waterings (plants, trees and palms require oxygen in the soil in addition to water). When a sump indicator rises it indicates there is excess water at the bottom of the planting pit and also in the bottom of the rootball, this accumulation of water can effectively suffocate the trees roots leading disease and/or anaerobic soil both of which can kill otherwise healthy trees.


If the sump indicator rises there are 2 options to mitigate the standing water:

1.) Test the percolation rate and determine if the water percolates quickly enough so that there is no standing water at least 1 day before the next watering. (1 day before to allow time for the soil to dry and macropores to form). Move on to “How to test Percolation Rate”.

2.) In very poor draining soils such as clay, or hard pan bottom like granite - pumping the sump until there is no more standing water may be the only option.

How To Test Percolation Rate (aka Water Infiltration Rate):

1.) Commence test prior to your next scheduled watering.

2.) Water tree, for more accuracy use a GPM meter from water source, take note of gallons applied (GPM can be roughly calculated using a 5 gal home depot bucket if no GPM is availible– link)

3.) Sump indicators engage and begin to rise.

(Note that some soils like sand the indicator may never rise, even if large amount of water are applied over long periods. In this case the water percolation outpaces the GPM available by the water source and a rate could not be determined unless a higher GPM source becomes available).

4.) Begin timing sump indicators decent once they reach the high water mark.

5.) Once sump indicator push nut has descended to the point where it rests on the top of the 4” cap stop timing.

6.) Take the time it took for the indicator to fall from its high water mark to resting on the cap and divide it by the gallons applied and that will give you the percolation rate.

ex: 85 gallons divided by 8 hours = 15 gallons/hr

7.) knowing the percolation rate of water through the rootball you can adjust watering in the following (3) ways:

a.) reduce the volume of water applied to the tree keeping the application rate the same (ex: filling watering basins with a hose).

b.) reduce the rate at which the water is applied (ex: soaker hose, drip irrigation) keeping the volume of water the same.

c.) reduce both the rate and volume at which the water is applied

8.) Keeping a record and adjusting the percolation rate vs the gpm applied will help determine an optimum watering schedule. Percolation rate can inform if your soil will require frequent, shallow waterings or infrequent, deep waterings.

Sand will usually have a very high percolation rate, so a very slow drip irrigation may be desired.

Ex: 60 gallons of water moves through a palm planted in sand in 1.5 hours, the percolation rate is 40 GPH (gallons per hour)

Conversely clay will have a very low percolation rate, so deep infrequent watering will be more beneficial.

Ex: 60 gallons of water moves through an oak tree planted in clay in 12 hours, the percolation rate is 5 GPH

List of factors/variables that can affect percolation in order of most impactful:

  • Volume and frequency of water applied

  • Current saturation of soil

  • Soil composition (sand, loam, clay) of both the plant material and planting pit where tree will be planted

  • Soil compaction (macropore vs micropore composition) of both the plant material and planting pit where tree will be planted

  • Proximity to slope (where water could run off a slope)

  • Soil PH and anions vs cations exchange present in soil make up

  • Tree species

               — time of year/weather

               — general climate

  • Other vegetation

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