{"product_id":"manual-geotextile-permeability-tester-constant-head","title":"Manual Geotextile Permeability Tester (Constant Head)","description":"\u003ch2\u003e\u003cspan\u003eManual Geotextile Permeability Tester (Constant Head) – QualiGTX™ GPT MN\u003c\/span\u003e\u003c\/h2\u003e\n\u003ch4\u003e\u003cspan\u003eConstant Head Permittivity Apparatus for Single-Layer Geotextiles\u003c\/span\u003e\u003c\/h4\u003e\n\u003cp\u003e\u003cspan\u003eThe QualiGTX™ GPT MN Manual Geotextile Permeability Tester determines the rate of water flow perpendicular to a single geotextile layer under a constant hydraulic head. A specimen clamp with a ø50 ± 0.5 mm bore secures the fabric across the flow path. Water passes through the specimen under a head differential of up to 250 mm, while the discharged volume is collected in a 1000 mL graduated cylinder and measured using a timer with 0.01 s resolution. Based on the collected volume, elapsed time, test area, and hydraulic head, laboratories can calculate the permeability coefficient and permittivity.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cspan\u003eDesigned for manual operation, this model allows technicians to control the valves, measure the collected water volume, and record test times directly. This straightforward configuration simplifies maintenance and verification. Laboratories conducting occasional permeability checks for quality confirmation, rather than continuous testing throughout production shifts, can obtain reliable measurements without the additional expense and calibration requirements of an automated system.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cspan\u003eThe specimen clamp accommodates materials up to 20 mm thick, making the apparatus suitable for heavy needle-punched nonwovens as well as thin woven and composite geotextiles. An integrated thermometer covering 0 to 50 °C monitors water temperature within the flow circuit. Since water viscosity changes with temperature, test results are normalized to a reference temperature before reporting. The complete unit requires a benchtop area of 500 × 550 mm and has a total weight of 36 kg.\u003c\/span\u003e\u003c\/p\u003e\n\u003ch2\u003e\u003cspan\u003eManual Geotextile Permeability Tester (Constant Head) – QualiGTX™ GPT MN Applications\u003c\/span\u003e\u003c\/h2\u003e\n\u003cp\u003e\u003cspan\u003eThe QualiGTX™ GPT MN is designed for laboratories evaluating the filtration and drainage characteristics of geotextile materials for manufacturing quality control, material procurement, and engineering design verification.\u003c\/span\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cspan\u003eNonwoven Geotextile Manufacturing\u003c\/span\u003e\u003c\/strong\u003e\u003cspan\u003e: Evaluates whether needle-punched and thermally bonded filter fabrics provide the water flow capacity specified in their product data sheets.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cspan\u003eWoven Geotextile Production\u003c\/span\u003e\u003c\/strong\u003e\u003cspan\u003e: Measures perpendicular water flow through woven filtration and separation fabrics, where the available open area influences hydraulic performance.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cspan\u003eDrainage System Design Verification\u003c\/span\u003e\u003c\/strong\u003e\u003cspan\u003e: Provides engineers with the flow measurements required to determine suitable filter layer dimensions behind retaining walls, along edge drains, and within blanket drainage systems.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cspan\u003eLandfill Leachate Collection\u003c\/span\u003e\u003c\/strong\u003e\u003cspan\u003e: Verifies the water flow capacity of filter geotextiles installed above drainage layers in landfill collection and cap systems.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cspan\u003eCoastal and Erosion Control Works\u003c\/span\u003e\u003c\/strong\u003e\u003cspan\u003e: Tests geotextile fabrics placed beneath riprap, gabions, and revetments, where inadequate filtration can result in soil loss.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cspan\u003eRoad and Railway Subgrade Drainage\u003c\/span\u003e\u003c\/strong\u003e\u003cspan\u003e: Assesses separation geotextiles designed to allow water passage while retaining fine soil particles under repeated loading conditions.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cspan\u003eContractor Incoming Inspection\u003c\/span\u003e\u003c\/strong\u003e\u003cspan\u003e: Checks delivered geotextile rolls against specified contract flow requirements before installation.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cspan\u003eThird-Party Testing Laboratories\u003c\/span\u003e\u003c\/strong\u003e\u003cspan\u003e: Provides cross-plane permeability testing capabilities through an apparatus that is straightforward to calibrate and suitable for audit verification.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003e\u003cspan\u003eManual Geotextile Permeability Tester (Constant Head) – QualiGTX™ GPT MN Key Features\u003c\/span\u003e\u003c\/h2\u003e\n\u003cp\u003e\u003cspan\u003eThe QualiGTX™ GPT MN features a straightforward hydraulic circuit and measurement arrangement designed to simplify constant-head permeability testing.\u003c\/span\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cspan\u003eConstant Head Operation\u003c\/span\u003e\u003c\/strong\u003e\u003cspan\u003e: Maintains a consistent hydraulic head throughout the test, allowing the discharge rate to stabilize and supporting repeatable measurements across different operators.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cspan\u003e250 mm Maximum Head Differential\u003c\/span\u003e\u003c\/strong\u003e\u003cspan\u003e: Accommodates the lower head settings required by filtration testing methods while providing additional capacity for higher-gradient testing of dense geotextile fabrics.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cspan\u003eø50 ± 0.5 mm Specimen Clamp\u003c\/span\u003e\u003c\/strong\u003e\u003cspan\u003e: Establishes a defined testing area through a precisely controlled bore diameter, ensuring accurate area values for permeability calculations.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cspan\u003e20 mm Specimen Thickness Capacity\u003c\/span\u003e\u003c\/strong\u003e\u003cspan\u003e: Supports thick needle-punched nonwoven and composite geotextile specimens without requiring clamp modifications.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cspan\u003e1000 mL Graduated Cylinder\u003c\/span\u003e\u003c\/strong\u003e\u003cspan\u003e: Provides sufficient collection capacity for measuring discharge over a meaningful time interval, minimizing the proportion of timing error in the final result.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cspan\u003eTimer Resolving to 0.01 s\u003c\/span\u003e\u003c\/strong\u003e\u003cspan\u003e: Measures elapsed test time with the precision required to maintain accuracy during short-duration, high-flow tests.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cspan\u003eIntegrated 0 to 50 °C Thermometer\u003c\/span\u003e\u003c\/strong\u003e\u003cspan\u003e: Monitors water temperature during testing to support the viscosity correction needed for standardized reporting.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cspan\u003eManual Valve and Reading Control\u003c\/span\u003e\u003c\/strong\u003e\u003cspan\u003e: Allows technicians to manage test operations directly, simplifying troubleshooting and reducing calibration requirements.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cspan\u003eCompact Benchtop Frame\u003c\/span\u003e\u003c\/strong\u003e\u003cspan\u003e: Features a 500 × 550 mm footprint and a total weight of 36 kg, allowing convenient placement while preserving workspace for specimen preparation.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003e\u003cspan\u003eTheory and Method\u003c\/span\u003e\u003c\/h2\u003e\n\u003cp\u003e\u003cspan\u003eWater flow through geotextile materials is governed by Darcy's law, which describes the relationship between flow velocity and hydraulic gradient using a coefficient that characterizes the material's permeability. Flow velocity is determined by dividing the measured discharge by the clamped specimen area. The ø50 mm bore provides a defined testing area of approximately 19.6 cm², ensuring that all collected water passes through a known cross-sectional area. The hydraulic gradient is calculated by dividing the applied head differential by the specimen thickness. By rearranging Darcy's law, the permeability coefficient can be calculated directly from the measured water volume, elapsed time, test area, hydraulic head, and specimen thickness.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cspan\u003eSpecimen thickness presents a particular challenge when measuring water flow perpendicular to geotextile fabrics, which is why permittivity is also used as an independent performance parameter. Nonwoven geotextiles can compress under applied pressure, meaning their thickness varies according to the load acting on the material. Permittivity addresses this limitation by expressing water flow per unit area under a unit hydraulic head, eliminating specimen thickness from the calculation. Both the permeability coefficient and permittivity can therefore be determined from the same test performed with this apparatus. Laboratories can report the appropriate parameter according to the applicable specification.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cspan\u003eAccurate results depend on controlling two important testing conditions. The first is water viscosity, which decreases as temperature increases. Consequently, the same geotextile specimen can allow more water to pass when tested with warmer water than when tested under colder conditions. The integrated thermometer monitors water temperature so the measured results can be corrected to a reference temperature.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cspan\u003eThe second consideration is dissolved air in the water. As water heats up inside the apparatus, dissolved air can escape from the solution and become trapped within the geotextile's pore structure. This gradually restricts water flow and can cause measured readings to decrease as testing continues. Using deaired water prevents this issue. Maintaining a constant hydraulic head also ensures consistent driving pressure, allowing the discharge rate to stabilize before the operator begins recording the test time.\u003c\/span\u003e\u003cspan\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003ch2\u003eManual Geotextile Permeability Tester (Constant Head) – QualiGTX™ GPT MN Technical Specifications\u003c\/h2\u003e\n\u003cdiv\u003e\n\u003ctable class=\"table table-style-align-center\" align=\"center\" border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"549\"\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eParameter\u003c\/th\u003e\n\u003cth\u003eSpecification\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eTest Method\u003c\/td\u003e\n\u003ctd\u003eConstant head, cross-plane (vertical) water flow\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMaximum Head Differential\u003c\/td\u003e\n\u003ctd\u003e250 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpecimen Clamp Inner Diameter\u003c\/td\u003e\n\u003ctd\u003eø50 ± 0.5 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMaximum Specimen Thickness\u003c\/td\u003e\n\u003ctd\u003e20 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTimer Range\u003c\/td\u003e\n\u003ctd\u003e0 to 99.99 s\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eThermometer Range\u003c\/td\u003e\n\u003ctd\u003e0 to 50 °C\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eGraduated Cylinder\u003c\/td\u003e\n\u003ctd\u003e1000 mL\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eVoltage\u003c\/td\u003e\n\u003ctd\u003e220 V (110V is also available)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDimensions (W × D × H)\u003c\/td\u003e\n\u003ctd\u003e500 × 550 × 600 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNet Weight\u003c\/td\u003e\n\u003ctd\u003e36 kg\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/div\u003e","brand":"Qualitest USA LC","offers":[{"title":"Default Title","offer_id":53459742490935,"sku":null,"price":100.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0786\/1859\/1543\/files\/manual-geotextile-permeability-t.webp?v=1793364514","url":"https:\/\/qualitest.us\/fr\/products\/manual-geotextile-permeability-tester-constant-head","provider":"Qualitest USA LC","version":"1.0","type":"link"}