CAUTION
58
Exercise 14
Tile System and French
Drain Construction
OBJECTIVE
The objective of this exercise is to properly construct a
french drain and a tile drainage system with an inlet.
TEXTBOOK REFERENCE
Information related to this activity can be found in the
Landscape Construction textbook in Chapter 12, Site
Drainage.
INTRODUCTION
Draining surface and subsurface water from a project
may be necessary to protect landscape improvements.
Solutions to drainage problems range from sloping the
French Drain to Store Excess
Surface Water
When a project has an enclosed, low area that is con-
excess runoff until it can percolate into the surrounding
soil. Please note that a french drain is not a permanent
solution to a drainage problem and will not work in
areas with heavy runoff. When the problem is short-term
• If the site will not accommodate a single trench,
the length may be split into separate trenches
placed at least 36 inches apart.
• Flag the location for each trench. To be effective
the trench should be located directly under the
wet area.
• Excavate a trench 1 to 2 feet wide and 42 inches
deep along the lines marked. In turf areas the sod
may be removed and set aside for reuse. Save
approximately 10% of the soil excavated from the
trench for cover.
entire bottom of the trench.
• Repeat this process with the other piece of
landscape fabric on the opposite side of the
trench.
• Fill the trench with 1 to 2 inch diameter washed
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Tile Systems to Drain Surface Areas
In areas where drainage problems are minor, but cannot
be solved through sloping or french drains, a tile system
minimum 1% rate from the highest inlet to the
outlet point.
• Beginning at the highest end of the trench, lay
4 inch diameter nonperforated tile that begins
running from the tee to approximately
12 inches above the surface. Continue laying
tile and inserting tees until the entire system
is complete. Apply duct tape around any
connections and joints to reduce the chance that a
connection pulls apart.
• Backfill the system to the surface, lightly
compacting the backfill after every 6 inch layer.
• At each inlet location, excavate the surface finish
grade to slope downward toward the riser.
• Cut each riser flush with the surrounding elevation
and place a premanufactured fiberglass inlet into
the end of the riser.
Exercise 14 Tile System and French Drain Construction 59
1’–2′
wide
2’–3′ Deep, fill with
rounded stone, length
varies according to
area to be drained
Weed barrier
Figure 14–1 French drain cross section.
Slope grade
to inlet
Inlet
Finish grade Cap for
cleanout
© Delmar/Cengage Learning.
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Tile Systems to Drain
Subsurface Water
Tile used to mitigate subsurface water problems is laid
out so as to cover the entire project site. Using paral-
lel tiles spaced according to the soil type, rainfall, and
severity of water problem, the water is intercepted and
PREREQUISITE EXERCISES
Students should have successfully completed Exercise5,
Tool Operation and Construction Techniques, before
beginning this exercise.
MATERIALS REQUIRED
• Survey stakes/flags
• Carpenter’s level
• Round-tipped shovels
• D-handled, flat spades
• Pick
EXERCISE DESCRIPTION—PART A
To complete this exercise trench and install a 10 foot long
french drain (Figure 14–3) with landscape fabric liner
and washed river rock fill. The drain should be 3 feet
60 Exercise 14 Tile System and French Drain Construction
EXERCISE DESCRIPTION—PART B
To complete this exercise trench and install a 20 foot
run of nonperforated 4 inch diameter tile with a honey-
comb surface inlet at one end. The tile should be placed
10′-0″
French drain
Cross section
30″
3′-0″
20′-0″
Figure 14–3 French drain plan and elevation.
© Delmar/Cengage Learning.
20′-0″
10′-0″
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