GRAVELLESS PIPE

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GRAVEL-LESS PIPE

• Bruce Lesikar
• Associate Professor
• Texas Cooperative Extension

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Gravel-less Pipe
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Gravel-less Pipe Drain Field
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Gravel-less Pipe Drain Field Materials /
Perforated Polyethylene Pipe

• 8 to 10 in Diameter
• 2 rows of holes along bottom of pipe.
• Holes 120 degrees apart.
• Synthetic Fabric wrapped around pipe.
• Available for use in Trenches and ET beds.

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Gravel-less Pipe Drain Field Bed Materials /
Trench

• Maximum length 150 feet.
• Width ranges 24 to 36.
• Level to within 1 in 25.
• Bottom depth at least 12 below tank outlet.

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Gravel-less Pipe Drain Field Materials / Fill

• Backfill trench with class Ib or II soil.
• Backfill ET bed with class II soil.

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Gravel-less Pipe Drain Field Separation Between
Components

• Minimum of 3 feet of undisturbed soil between
  trenches.

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Gravel-less Pipe Drain Field Depth of
Installation

• 18 Minimum Depth.
• 36 Maximum Depth.
• Greater than 26 inch Rainfall Region.
• 60 Maximum Depth
• Less than 26 inch Rainfall Region.

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Gravel-less Pipe Drain Field Treatment Method

• Pipe distributes wastewater to soil
• Pipe stores wastewater until percolation into
  the soil.
• Geotextile fabric keeps soil out of pipe.
• Soil provides treatment of the wastewater.

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Gravel-less Pipe Drain Field Pretreatment
Required

• Septic tank

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Gravel-less Pipe Drain Field Separation
Distances

• Restrictive horizons 2 feet
• Groundwater 2 feet

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Gravel-less Pipe Drain Field System Sizing
Requirements/ General Description

• Absorption surface
• Bottom width plus 1 foot of side wall on each
  side of the trench

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Gravel-less Pipe Drain Field System Sizing
Requirements/ Area Required

• Based on soil hydraulic loading rate
• Area daily wastewater flow / loading rate
• A Q / Ra

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Gravel-less Pipe Drain Field - System Sizing
Requirements/ Sizing Equations

• Determine the length of trench.
• Assume 2 of sidewall for each foot of trench.
• 8 Gravel-less pipe use bottom width 2
• 10 Gravel-less pipe use bottom width 2.5
• Trench length Area/( bottom width 2)
• L A / (W 2)

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Gravel-less Pipe Drain Field System Sizing
Requirements/ Determine the Number and Length of
Trenches

• Evaluate lot dimensions
• Evaluate required setback distances
• Evaluate the slope of the lot
• Select trench lengths which fit the site