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Landscape Drainage Design Assistance

A. Vertical applications

1. Plan the layout for collector lines.

a. Plot a path through the lowest area to an acceptable discharge point. The discharge point can be a ditch, the street, a catch basin, another drain line or a declining hillside. Wherever possible, keep the collected water on-site storing it in decorative ponds or using it in irrigation.

b. Begin planning at the discharge point, the lowest elevation of the system, and proceed toward the highest point of the area to be drained.

c. Plan the placement of branch lines from the main line.

i.  These branches may be at regular intervals to provide even drainage to an entire area. 10-15 foot spacings are ideal under most conditions.

Or

ii.  These branches may reach out into low lying problem areas.

2. The size of the Multi-Flow, 6, 12, or 18-inch, will be determined by the total length of the collector system. Frequently it makes good sense to use a larger size (usually 12-inch) for the trunk line and a smaller size (usually 6-inch) for the branch lines.

3. Larger systems
In larger areas it will be necessary to empty the collector lines into a transport system more frequently.

a. As a guideline assume that:

i.  A line of 6-inch Multi-Flow could reach full capacity after about 136 feet of water collection.

ii.  12-inch Multi-Flow could drain up to 235 feet of length before it reaches capacity.

iii. 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.

b. The neatest way to accomplish this is to locate the transport pipe in the trench below the central trunk collector line.

c. Connecting to transport system
Smooth, solid, rigid pipe makes for the most reliable transport system. PVC, ABS, or dual wall corrugated all work well.

i.   In some cases, especially in larger systems, 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. A standard 3-inch PVC or ABS elbow or tee can be slipped over the Multi-Flow connector. Pipe glue will ensure a lasting connection.

ii.  In some situations, especially in smaller systems, it is best to discharge the water through an end outlet or side outlet. In these cases, cut the plastic membrane covering the opening of the outlet. Cut the hole so that the exit pipe fits snugly and is located at the bottom of the fitting. Insert the exit pipe into the opening and seal the joint using wide waterproof PVC tape. 3-inch pipe is used with 6-inch Multi-Flow; 4-inch pipe is used with 12 and 18-inch Multi-Flow.

4. Backfilling
Use clean very coarse sand to fill the trench. Multi-Flow should be positioned in the center of the trench while backfilling. Specify that the sand extend to the surface or near to it. Never allow installers to cap the trench with clay or other dense material. See Selecting Backfill Material for more information on this topic.


B. Horizontal applications

1. Plan the layout for collector lines.
Usually horizontal installations do not require trenching. When used in new constructions settings such as in planters, under playground equipment, in golf greens, or under synthetic turf, Multi-Flow can be laid out over the prepared site prior to bringing in fill. Establish a route for the trunk line from the system high point to the discharge point. The discharge point can be a ditch, the street, a catch basin, another drain line or a declining hillside. Wherever possible, keep the collected water on-site storing it in decorative ponds or using it in irrigation.

If trenching is required, maintaining grade is especially critical.

Additional branches can be laid out randomly or in a pattern using wyes for a herringbone pattern or crosses for a grid pattern.

2. Connecting to the transport system

a. Smooth, solid, rigid pipe makes for the most reliable transport system. Three-inch pipes are used to make these connections.

b. There are several ways to transition to the transport pipes:

i.  Connection to the transport system will usually be made with a multi-purpose outlet (taking in water from one side 0600M, 1200M, or 1800M) or a multi-purpose connector (taking in water from two sides 06009, 12009, or 18009).

ii.  In the 6-inch line, horizontal double wyes and horizontal crosses also make good outlets. (06016 and 06018)

iii. Side outlets in all three sizes are also occasionally used for outletting horizontally. (06003, 12003, and 18003)

c. A standard PVC or ABS elbow or tee will typically be used for all of these transitions. Pipe glue will ensure a lasting connection.

3. Backfilling
Using clean very coarse sand to cover the Multi-Flow drain will ensure its longevity. One to 2 inches of sand should be spread over the drain and sand should extend 3 to 6 inches on each side of the Multi-Flow. Never bring in fill containing clay or other dense material. See Selecting Backfill Material for more information on this topic.

 

How Artificial Drainage Works
Sample Landscape Drainage Drawings

Multi-Flow Installation Advice