ground percolation testing

Ground Percolation TestingHow long will it take for a latrine to fill

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What kind of latrine are we talking about?


What is a percolation test

Method to determine how fast water (urine) will flow into the groundA tool to determine an appropriate site for a latrineA tool to determine how soon the tank or pit will fillCan be used to size a simple leach-field


Where do the liquids go?

Liquids leak into soil, but only so much per day . . . We’ll calculate how much. With time, fecal sludge builds up and closes off the tank floor – it will fill faster after that.


What we’ll calculate

1. How fast water is absorbed by the soil – in three steps2. How much liquid will enter the latrine per day 3. How large of a soil area will be needed to get rid of the liquids each day

We are going to make our calculations for a pour-flush toilet because it uses a lot more water than a pity latrine.


First – dig a hole and smaller test hole


Second – pre-soak the hole


Third – start test and record data


Example calculation



1. How fast water is absorbed by the soil – in three steps 2.1 minutes/cm

2. How much liquid will enter the latrine per day 3. How large of a soil area will be needed to get rid of the liquids each day


Calculating liters of liquid per day

Urine related liquids:

Average person pees a total of 1.5 liters per day, they pee about 5 times per day, but they do not pee each time in a latrine.

We will assume they pee 0.4 liters each time they pee. We will assume they pee twice a day in the latrine.Assume the average flush after peeing is 2 liters.

Total peeing related liquid is 2 x (0.4 + 2) = 4.8 liters per person per day


Calculating liters of waste per day

Fecal related liquids: Assume the average person poops 1.25 times per dayThe average flush after pooping is 3 liters of water.Therefore there are 1.25 x 3 = 3.75 liters of liquid due to pooping in the latrine

per person per day.

Assume 5 people per household

Total liquid is 5 x (3.75 + 4.8) = 43 liters of liquid per household per day



1. How fast water is absorbed by the soil – in three steps 2 minutes/cm

2. How much liquid will enter the latrine per day 43 liters per day for this household

3. How large of a soil area will be needed to get rid of the liquids each day


Soil Area Needed for Liquid Absorption


The soil percolation rate is 2.1 minutes per cm The suggested soil treatment area is 0.02 sq. meters/liter We have 43 liters per day so the suggested area is 43 x .02 = 0.86 sq. meters

Perc rate > 24 minutes per cm will fill septic tank very soon Perc rate < 3 seconds per cm has a high probability of contaminating wells that are

nearby.

Percolationrate

Soil treatmentarea

Area needed for our example household

Minutesper cm

Square metersper liter per day

Square meters

0.04 to 2 0.02 0.9

2.5 to 6 0.03 1.3

6.3 to 12 0.04 1.7

12.3 to 18 0.05 2.2

18.3 to 24 0.06 2.6

The “take away” on percolation testingA simple test can avoid dissatisfaction.The “standard” pour-flush toilet design (three rings) is marginal for anything

other than sandy soils. Lower percolation rate = Low emptying frequencyHigh percolation rate = High emptying frequencyVery-low percolation rate = Risk of contaminating wellsFecal sludge buildup will always hinder percolation

We recommend the following design for testing . . .


Recommended design changes


Thank you and good luck.


Ground Percolation TestingAdditional sources of information:http://www.extension.umn.edu/distribution/naturalresources/DD0583.htmlhttp://www.deq.gov.mp/artdoc/Sec6art108ID255.pdf

www.naturehealingnature.org mark@naturehealingnature.orgwww.thecenterforrainwaterharvesting.org 016-685-915 & +1 832-423-8425

Empowering people to help themselves with what they already have . . .

ground percolation testing

Documents

pity latrine

kind of latrine

soil area

calculating liters of

calculatehow fast water

fast water urine

liquids leak

dayurine related liquids