Geotextile Permeability Apparatus (Permittivity)
Constant and falling head apparatus for water flow normal to the plane of a geotextile, giving the permittivity figure a drainage or filtration layer is specified on.
Typical applications
- Filtration and drainage design for geotextiles
- Subsurface and edge drainage specification
- Erosion control and revetment underlays
- Incoming quality control against a stated permittivity
Conforms to
- ASTM D4491/D4491M—Water permeability of geotextiles by permittivity
- EN ISO 11058—Geotextiles and geotextile-related products — Determination of water permeability characteristics normal to the plane, without load
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Add as many products as you need and send one enquiry covering all of them, or send this item on its own. Bulk and drum quantities are quoted on request.
Worth knowing before you order
The source is a supplier display panel that names this instrument and prints no specification for it — no specimen diameter, no head range, no tank capacity. The rows above describe what the two standards require, not what this particular model is built to. Two practical points before you order: the water has to be de-aired or the result drifts, and ASTM permittivity and the EN ISO velocity index are different numbers that cannot be converted into each other.Specification
| Determines | Permittivity in s⁻¹ and the flow rate through the fabric normal to its plane |
|---|---|
| Heads | Constant head and falling head, both described by ASTM D4491 |
| EN ISO reporting | EN ISO 11058 reports a velocity index — the flow velocity at a 50 mm head |
| Water condition | De-aired water. Dissolved air comes out of solution against the fabric and changes the reading, so a de-airing tank is part of the rig, not an accessory |
Support available
- Installation & commissioning
- Calibration
- Spares & consumables
Calibration is arranged through NABL-accredited laboratories under the relevant scope. We state the scope and the certificate number on the quotation — see what accreditation actually covers.
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