It is common to keep the top of the Multi-Flow line 6 inches below
the surface. Actual depth will be determined by factors such as:
anticipated depth of maintenance practices
desired depth of desaturation
• width of area to be drained
• required response time
• speed at which full drainage is desired
• subsurface physical features
• the location of irrigation lines.
Subsurface drainage of turf is most effective within 5 to 8 feet
of the drain line. Therefore, 10 to 16 foot spacings are ideal.
On sloped surfaces a wider spacing is acceptable because gravity
will aid in bringing water to the drain line. In fairways, a central
collector line running up the center, with arms reaching out into
low lying areas on either side, is frequently the best course
C. Product size selection and line length limits
A line of 6-inch Multi-Flow could reach capacity after about 136
feet of water collection. 12-inch Multi-Flow could drain up to
235 feet of length before it reaches capacity, while 18-inch Multi-Flow
could extend up to 360 feet. These lengths are based on the assumption
that the line is collecting water from a 12 foot wide area during
a one inch in one hour rainfall event.
After water has been collected by the Multi-Flow system, it must
be transferred to a transport system for its removal from the
site. This maximizes the total output of the system in a given
amount of time. Sometimes the water is discharged into a storm
sewer, stream, lake, or pond. Increasingly, it is collected for
reuse in irrigation.
transport lines need to have a carrying capacity at least equal
to the sum of all of the collector lines they are called on to
service. For planning purposes it is useful to assume these numbers:
6-inch ..................17 gpm
there is any danger that the water level at the discharge point
will rise higher than the level of the collection system, a check
valve should be installed on the discharge pipe. This will avert
water from backing onto the course and also prevent contaminated
water from backing up into the collector lines and causing siltation.
to transport system
connection to the transport system will be made with a multi-purpose
connector. Most commonly this will be a 0600M, 1200M, or 1800M.
These connectors empty from the bottom. Smooth, solid, rigid
pipe makes for the most reliable transport system. Use of pipe
cement will ensure a lasting connection. Multi-purpose connectors
join to 3-inch PVC elbows and tees. When a multi-purpose connector
is used, the transport pipe is located beneath the level of
the collector pipes.
some situations it is preferable to discharge the water through
an end outlet or a side outlet (e.g. 06003 or 06004). In these
cases, cut the plastic membrane covering the opening of the
outlet so that the exit pipe fits in snugly and is located at
the bottom of the fitting. Insert the exit pipe and seal the
joint using PVC pipe tape to prevent soil intrusion. 6-inch
Multi-Flow connectors attach to a 3-inch PVC while 12 and 18-inch
Multi-Flow match 4-inch PVC. When an end or side outlet is used,
the transport pipe is located at the same level as the bottom
of the collectors.
an end or side outlet is used, the transport pipe is located
at the same level as the bottom of the collectors.
a multi-purpose connector is used, the transport pipe is located
beneath the level of the collector pipes.
Use clean very coarse sand to fill the trench. Hold Multi-Flow
in the relative center of the trench while backfilling. Centering
devices are helpful in this task. Bring the sand up to the surface
or near to it. Jetting the sand-filled trench with water will
help to settle the sand in place more quickly. A small vibratory
packer also works well. Topsoil can be blended with the sand at
the surface of the trench to create a better turf growing medium.
Never, however, cap the trench with clay or other dense, impermeable
Selecting Backfill Material
for more information on this topic.
Green drainage theory
Whether it is on a USGA-style layered green, a California-style
single material green, or even a push-up style green, an effective
subsurface drainage system is a must. Assuming that the green
has been constructed using porous materials, water will soon arrive
at the relatively impermeable subbase. If it does not have an
easily accessible escape route from here, the green will become
saturated. This invariably results in unacceptable growing and
primary considerations influence subsurface golf course green
drainage plans and practices:
Does the system provide adequate drainage?
• Will the system be damaged by maintenance practices?
• Will the system avoid future failure and blockage?
addresses these concerns by providing systems that are:
2.) intensively patterned
3.) adequately filtered
Multi-Flow’s structure and shape provide unique drainage
advantages. Its wide profile provides superior surface area
allowing more opportunity for water to enter the system. Its
superior strength significantly reduces the risk of being crushed.
And its internal flow characteristics allow water to leave the
green area quickly.
it need not be trenched in but is simply rolled out over the
subgrade where it lies out of reach of cup cutters and coring
equipment. (See Applications:
Conventional wisdom has often placed drainage collector lines
only in the low points of the green subbase. The assumption
was that since water will find these low-lying areas anyway
and since greens allow water to move freely, this is all that
practice overlooks the effect that moving water has on the structure
of the green. Moving water carries fine particles with it. The
more water that moves and the higher velocity at which it moves,
the more soil it will carry with it. Installing drain lines
further apart requires that water move in greater volume to
fewer collection points. This results in greater soil migration
which causes a break down of the soil structure and a potential
blocking of drainage lines.
on a golf green should be gentle and thorough. Intensive patterning
decreases the velocity of the water movement and consequently
protects the fragile integrity of the green structure. Spreading
drainage lines out over the entire subgrade of the green means
that water has less distance to travel and results in less soil
lines closer together also ensures a prompt and thorough drainage.
Look at the veins on the back side of a leaf for a model of
effective drainage. The less distance water needs to travel
to reach an escape route, the better the drainage is. Intensively
patterned drainage allows for the removal of significant amounts
of water in a short time without disrupting the structure of
With closely spaced Multi-Flow lines, particle
movement is significantly reduced. This increases drainage
efficiency and dramatically extends the life span of the
veins on a leaf are a model of effective fluid transfer
in nature. It is also true on a golf green: the less distance
water needs to travel to an escape route, the better the
intensive pattern in a herringbone configuration provides
uniform drainage to every part of the green.
Two separate filters assure that the drainage system will not
fail. Multi-Flow’s 4 ounce, needle-punched geotextile
wrap prevents sand from entering the flow channels. Two inches
of clean, very coarse sand effectively protects the geotextile
from blockage due to silt and other soil fines.
System design and layout
When designing drainage for a green, the main Multi-Flow collectors
should lie horizontally on the subgrade and be placed along
the line of maximum fall. A 4-inch PVC pipe should be placed
directly below the main line, exiting the green at the low end.
PVC tees must be installed in the PVC lines, pointing upward,
at each location where a Multi-Flow double wye will connect
to the laterals. The PVC pipe should be backfilled with native
soil, leaving only the opening to the PVC tee exposed and lying
flush with the soil surface.
If a geotextile fabric is to be used as a barrier between unstable
subsoil and the gravel drainage blanket as in a USGA green or
between the subsoil and the green mix as in a California style
green, it should be installed at this time, and openings should
be cut into the barrier fabric for the PVC tees to emerge through.
Typically, the barrier fabric should not cover the Multi-Flow
drainage product. Locate lateral Multi-Flow collectors across
the slope of the subgrade, allowing a natural fall to the main
line, where they will connect into the double wye.
Lateral lines should be spaced not more than 12 feet apart and
extended to the perimeter of the green. Lines should be placed
in water-collecting depressions, if they exist.
If the green exceeds 100 feet in width, an additional herringbone,
or half herringbone, must be installed along one side of the
original pattern in order to maintain maximum flows.
At the low end of the gradient, adjacent to the main line’s
exit from the green, vertical drainage product should be placed
along the perimeter of the green, extending to the ends of the
first set of laterals. This smile drain will facilitate drainage
of the water that may accumulate at the low end of that drainage
area. The vertical drainage product can be discharged into the
4-inch PVC pipe by way of a Multi-Flow connector, such as a
06009, and a PVC tee as it exits the green.
Wherever the grade exceeds 3%, stakes should be placed to prevent
movement of the Multi-Flow during later stages of construction.
Avoid applying more than 6,000 psf to the Multi-Flow during
construction. Once the 2-inch band of sand is in place, additional
pressure on the Multi-Flow is permissible.
The geotextile filter fabric should be securely taped to all
fittings to prevent the infiltration of sand or soil during
Maintain a grade of at least .5%; 1% is preferable.
If the PVC transport system terminates in a stream or pond that
is likely to reach the height of the exit pipe, a check valve
must be installed to prevent back flow through the drainage
Backfill material may be the single most important factor affecting
the longevity of a drainage system. Sand functions as an excellent
filtration tool, removing silt and clay particles, while allowing
water to pass through. A 2 inch band of very coarse sand should
be installed covering the top and sides of each collector line.
See “Selecting Backfill Material”
for more information on this topic.
Artificial Drainage Works
Sample Golf Course Drainage Drawings