OSSF DR UPDATED 2026 EXAM SCRIPT QUESTIONS AND
SOLUTIONS SCORED A+
✔✔How must drainfield trenches be installed? - ✔✔Level
✔✔Should drainfield trenches be sloped? - ✔✔No
✔✔What is the standard gravity pipe slope in Texas? - ✔✔¼ inch per foot
✔✔¼ inch per foot equals approximately what percent? - ✔✔2%
✔✔What is the formula for pipe drop? - ✔✔Length (ft) × 0.25 = inches of drop
✔✔How much drop is required for 40 feet of pipe? - ✔✔10 inches
✔✔How much drop is required for 60 feet of pipe? - ✔✔15 inches
✔✔What happens if the slope is too steep? - ✔✔Solids carry over
✔✔What happens if the slope is too flat? - ✔✔Solids settle and clog
✔✔What is prohibited over a drainfield? - ✔✔Driving heavy equipment
✔✔When is an inspection required? - ✔✔Before covering the system
✔✔Who gives final system approval? - ✔✔Designated Representative or permitting
authority
✔✔Can Installer I change system design in the field? - ✔✔No
✔✔Can Installer I adjust pipe slope per design? - ✔✔Yes
✔✔Can local authorities be more restrictive than state rules? - ✔✔Yes
✔✔Can local authorities be less restrictive than state rules? - ✔✔No
✔✔What test measures soil absorption? - ✔✔Perc test
✔✔Does Installer I size drainfields? - ✔✔No
✔✔Who issues the Installer I license? - ✔✔TCEQ
✔✔How many feet is 24 inches? - ✔✔2 feet
SOLUTIONS SCORED A+
✔✔How must drainfield trenches be installed? - ✔✔Level
✔✔Should drainfield trenches be sloped? - ✔✔No
✔✔What is the standard gravity pipe slope in Texas? - ✔✔¼ inch per foot
✔✔¼ inch per foot equals approximately what percent? - ✔✔2%
✔✔What is the formula for pipe drop? - ✔✔Length (ft) × 0.25 = inches of drop
✔✔How much drop is required for 40 feet of pipe? - ✔✔10 inches
✔✔How much drop is required for 60 feet of pipe? - ✔✔15 inches
✔✔What happens if the slope is too steep? - ✔✔Solids carry over
✔✔What happens if the slope is too flat? - ✔✔Solids settle and clog
✔✔What is prohibited over a drainfield? - ✔✔Driving heavy equipment
✔✔When is an inspection required? - ✔✔Before covering the system
✔✔Who gives final system approval? - ✔✔Designated Representative or permitting
authority
✔✔Can Installer I change system design in the field? - ✔✔No
✔✔Can Installer I adjust pipe slope per design? - ✔✔Yes
✔✔Can local authorities be more restrictive than state rules? - ✔✔Yes
✔✔Can local authorities be less restrictive than state rules? - ✔✔No
✔✔What test measures soil absorption? - ✔✔Perc test
✔✔Does Installer I size drainfields? - ✔✔No
✔✔Who issues the Installer I license? - ✔✔TCEQ
✔✔How many feet is 24 inches? - ✔✔2 feet
