How long will it take for a latrine to fill & Empowering people to help themselves with what they already have...

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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 ground A tool to determine an appropriate site for a latrine A tool to determine how soon the tank or pit will fill Can 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 steps 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 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 &

What we’ll calculate 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 ( ) = 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 day The 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 ( ) = 43 liters of liquid per household per day &

What we’ll calculate 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. Percolation rate Soil treatment area Area needed for our example household Minutes per cm Square meters per liter per day Square meters 0.04 to to to to to

The “take away” on percolation testing A 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 frequency High percolation rate = High emptying frequency Very-low percolation rate = Risk of contaminating wells Fecal sludge buildup will always hinder percolation We recommend the following design for testing &

Recommended design changes &

Thank you and good luck &

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