What Size Corrugated Pipe Coupler Do I Need

10 Steps to Easy Surface Drainage Design

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Basic drainage design is relatively simple by following this piece of cake 10-step procedure.

Before we starting time there are four of import points to remember:

Excess water e'er collects at the everyman elevation points.
Blueprint for worst case weather and non for average conditions.
Although obvious, water can only flow downhill.
Be generous in the pattern-if in doubt add an extra drove indicate (grate) and rather oversize than undersize a component.

In society to aid empathize the bones steps of designing a drainage system, consider the following example:

A contractor needs to install a drainage arrangement in the backyard of a house in Atlanta, Georgia. The backyard is comprised of 3 areas, a loamy soil bloom bed, a grass expanse and a concrete deck. The flower bed area is 6' broad x xx' long (area of 120 sq ft), the grass expanse is 20' wide ten 24' long (area of 480 sq ft) and the physical deck area is 40' broad ten xx' long (area of 800 sq ft). The altitude from the backyard to the street is 100′.

Footstep ane:
Determine the Rainfall Intensity of the holding.

Unlike parts of the land accept varying rainfall intensity profiles. Employ Table 1.i beneath to determine the Rainfall Intensity (I) of the property. Keep in mind that the table below has been simplified (more sophisticated data is available on the web that incorporate 100 year 1-hour rainfall maps, etc.)

Table 1.1

Rainfall Intensity Zone	States in the U.s.a.	Rainfall Intensity
Zone A	AL, FL, GA, Hi, LA, MS, NC, OK, SC, TN, TX	5.0 inches per hr
Zone B	AR, CT, DE, DC, IA, IL, IN, KS, KY, MA, Md, MI, MN,MO, ND, NE, NH, NJ, NY, OH, PA, RI, SD, VA, WV, WI	3.5 inches per hour
Zone C	AK, AZ, CA, CO, ID, ME, MT, NV, NM, OR, UT, VT, WA, WY	2.0 inches per 60 minutes

As the property in our example is in Atlanta, GA, it falls into Rainfall Intensity Zone A with a Rainfall Intensity of 5.0 inches per hour.

Footstep two:
Summate the maximum run-off potential flow for each area.

In order to correctly size the drainage pipe network, the maximum run-off menstruation for each area must be calculated. A oft used formula for calculating the maximum runoff potential from a minor area (under 200 acres) is the Rational Method. The Rational Method Formula is:
where:
Q = peak runoff menstruation (gallons per minute)
C = coefficient of runoff
I = rainfall intensity (inches per hour)
A = drainage area (foursquare feet)

For our example, we already know the area (A) of each zone to be drained. The flowerbed is 120 sq feet, the grass area is 480 sq anxiety and the concrete deck area is 800 sq anxiety.

Next, we will determine the coefficient of runoff (C) for the surface type of each surface area to be drained using Tabular array 2.1 beneath. The coefficient of runoff for the loamy soil flowerbed is 0.45, for the grass area is 0.35 and for the concrete deck expanse is 0.90.

Table ii.1

Surface Type	Coefficient of Runoff
Concrete or Asphalt	0.90
Dirt	0.60
Gravel	0.50
Loam	0.45
Sand	0.forty
Grass	0.35

Lastly, we will use the Rational Formula to calculate the peak runoff flows for each area.

For the flowerbed: Q = (0.45 x five.0 10 120) / 96 = two.8 gallons per minute
For the grass: Q = (0.35 10 5.0 x 480) / 96 = 8.eight gallons per infinitesimal
For the concrete deck: Q = (0.90 10 v.0 x 800) / 96 = 37.v gallons per infinitesimal

Adding these together, the total combined surface area maximum runoff flow (Q) is 49.1 gallons per minute.

Step 3:
Choose the number of drainage zones.

When designing a drainage system, attending must be paid not to exceed the maximum flow capacities of the drainage piping (every bit prove in Tabular array 3.1 below). Using either 3″, 4″ or 6″ drainage pipage is recommended on well-nigh residential and low-cal commercial projects every bit these piping sizes and applicable fittings are readily available and easy to install.

Table 3.i

Pipe Size	Maximum Flow Capacity
3″	44.0 GPM
4″	75.0 GPM
6″	175.0 GPM

In our example and using Table 3.ane above, there are two choices to arrange the maximum property run-off catamenia calculated in step 2 of 49.one GPM.

A unmarried iv″ or larger pipe may be used (a unmarried Drainage Zone system).
Two separate 3″ or larger pipes with two belch points could be used (a ii Zone Drainage organisation).

For the instance we are using, every bit 3" pipage is easier to install and cheaper than iv" or 6" pipe, we will select a two Drainage Zone system using 3" pipe with two independent discharge points. Even so, if four" or 6" pipe is more readily available than 3" pipe, you lot may choose to use that instead.

Drainage Zone 1 will incorporate the flowerbed area and the grass area (maximum run-off flow for that combined area is 11.6 GPM) and Drainage Zone 2 (maximum run-off catamenia is 37.5 GPM) will incorporate the concrete deck area.

Step 4:
Locate the basin and/or grate positions.

Locate the low spots on the property where excess water could accumulate. Once these are finalized, they get the basin and/or grate locations. In the case above, allow united states of america presume that each of the 3 areas described has a unmarried low point within its confines. The outset bowl and/or grate is located in the flowerbed, the second basin and/or grate is in the grass surface area and the third basin and/or grate is in the concrete deck. If there is more than than one depression point inside an surface area, each of these would be a drove point and a location for a basin and/or grate.

Pace 5:
Decide whether a flat or atrium (domed) grate is advisable.

Flat grates are typically used in areas where there is pedestrian, wheelchair, or light duty auto traffic. Atrium grates are domed and typically used where in that location is no pedestrian traffic and where mulching, leaves, or other debris could be present that could plug the flat grate.

In the previous example problem, presume that the flowerbed has been mulched and leaves may too be present. Therefore an atrium grate (Grate ane) is recommended. For the grass area, a flat grate (Grate two) must be used equally at that place will be lawnmower and pes traffic nowadays. For the concrete deck area, a flat grate (Grate 3) must also exist used.

Step 6:
Select the appropriate grate size for each expanse.

Using the maximum runoff flows from each area that we calculated in Step 2, carve up each expanse'due south flow by the number of grates locations in that expanse to calculate how much flow each grate needs to handle. One time y'all accept calculated each grate'southward flow requirements, utilise Tabular array half dozen.1 below to select the grates.

Table half dozen.i

Grate	Maximum Flow Chapters
iii″ Circular Flat	iii GPM
4″ Round Apartment	half dozen GPM
6″ Circular Flat	16 GPM
6″ Square Universal	xi GPM
9″ Square Flat	50 GPM
12″ Square Apartment	70 GPM
18″ Foursquare Flat	120 GPM

Grate	Maximum Flow Capacity
three″ Atrium	12 GPM
four″ Atrium	xx GPM
half-dozen″ Atrium	36 GPM
nine″ Atrium	twoscore GPM
12″ Atrium	65 GPM

Grate	Maximum Period Capacity
iii″ Brass	iv GPM
4″ Brass	7 GPM

In the case, for the flowerbed area (with only 1 grate location) and a maximum runoff flow of two.8 GPM, we cull a 3" atrium grate, which has a maximum flow rate of 12 GPM. For the grass area (with only 1 grate location) and a maximum runoff menses of 8.8 GPM, we choose a vi" round apartment grate which has a maximum flow rate of 16 GPM. For the concrete deck area (with only one grate location) and a maximum runoff menstruation of 37.five GPM, nosotros choose a 9" flat grate which has a maximum flow rate of fifty GPM.

Equally we previously decided to use all three" drainage pipage, check on Table 6.two beneath that all of the grate sizes chosen can be used with iii" pipe.

Tabular array 6.2

Grate Size	Pipe Diameter Options
iii″	3″ pipe connecting directly on to grate
iii″ Brass	2″ Schedule forty or 3″ pipe ¹
4″	four″ pipe connecting direct on to grate
4″ Brass	three″ or 4″ pipe ²
six″	half-dozen" pipe and 3" or 4" pipe when used with 6" grab basin
half dozen″ Universal	3" or 4" piping when used with or without 6" catch basin
9″	3", four" or 6" pipe when used with ix" catch bowl
12″	three", iv" or 6" piping when used with 12" take hold of basin
xviii″	3", four" or 6" pipe when used with eighteen" catch basin

Fits 2" Schedule 40 pipe attaching directly to PVC collar or fits 3" piping via 3" S&D fitting.
Fits 3" pipe attaching directly to PVC collar or fits 4" piping via 4" S&D plumbing equipment.

There are no catch basins available for 3" or four" grates as they connect directly to drainage pipe. When using the 9", 12" and 18" grates a catch basin or depression contour basin must exist used. The only time a decision needs to be made is when using a half dozen" round or half-dozen" foursquare grate. In our example, a grab basin must exist used for the vi" grate because nosotros are connecting it to a three" pipe.

In our example, all iii can indeed be used with three" pipe. The 3" grate will connect directly to three" pipe, the 6" grate will connect to the 3" pipe using a 6" catch bowl and the 9" grate will connect to 3" pipe using a 9" take hold of basin.

However, if say the flowerbed surface area had been 600 sq ft instead of 120 sq ft, the Rational Method formula in Stride 2 would take increased the maximum runoff flow from 2.viii GPM to fourteen.ane GPM. The 3" atrium grate that you lot had previously called would non have been adequate and a 4" atrium grate would exist required. In this case, you would need to use 4" pipe for the drainage system. If you still preferred to use 3" pipe, and then a suggestion would exist to use two adjacent 3" atrium grates (each grate would so handle just over 7.0 GPM which is within its maximum capacity of 12 GPM).

Note: There are three common types of drainage pipe and fittings that are used. Tempo'southward grates are designed to be used with all of them. Please refer to the Appendix at the end of this guide for more information on the different types of drainage pipes and the appropriate fittings.

STEP 7:
Select the grate colors.

The most normally used grate color for grass areas is green. When used with concrete applications, grayness grates may be the most appropriate color. In other areas however, grate colors are more a affair of personal preference. In Table seven.one beneath, you can run into the different colour options available.

Tabular array vii.1

Grate Description	Available Colors
3″ Round Flat Grate	Dark-green / Black / Sand / Grayness / Royal
3″ Round Atrium Grate	Greenish / Black / Sand
3″ Circular Apartment Grate and PVC Collar	Brass
iv″ Round Flat Grate	Green / Blackness / Sand / Grey
iv″ Circular Atrium Grate	Green / Blackness / Sand
4″ Round Flat Grate and PVC Collar	Brass
6″ Round Apartment Grate	Green / Blackness / Sand / Greyness
6″ Circular Atrium Grate	Greenish / Black / Sand
6″ Square Apartment Universal Grate	Green / Black / Sand / Grey
9″ Square Apartment Grate	Greenish / Blackness / Sand / Grey
9″ Square Atrium Grate	Greenish / Black
12″ Square Flat Grate	Light-green / Black / Sand / Grey
12″ Foursquare Atrium Grate	Green / Blackness
18″ Square Flat Grate	Green / Black / Sand / Grey

STEP 8:
Decide where to re-route this water.

There are many options for re-routing the h2o that is collected in the grates and piping. Some of the most mutual applications for re-routing the water are to the street curb, to a storm water drain, to another landscaped area that can safely handle large volumes of water, to a French drain or to a storage tank that would allow for irrigation at a after time.

Let us assume that for this project, the run-off water will be re-routed to the street curb. Recall that the h2o must flow merely downhill (fifty-fifty a modest uphill section will foreclose your system from draining properly). As the distance that the run-off water needs to travel is 100 ft, the recommended meridian drop from any grate to the discharge bespeak must be a minimum of ii' or 24". (Minimum recommended slope should be 24" per 100 ft or approximately i/four" per foot). For optimum results this slope should exist fairly uniform.

If the natural topography of the area to be tuckered does not have the necessary autumn to meet the minimum slope requirements, you volition need to dig a trench with the minimum slope required and so use a combination of low profile basins and catch basins, some of which will take 1 or multiple risers to make sure that grates end upward at grade level.

STEP 9:
Design piping network.

There are 2 options for the 3" pipe network for the grass and flowerbed areas. These grates can either be plumbed inline or have two separate three" drainage pipes that are after connected into a single 3" discharge pipe.

The plumbing for the drainage pipage from the concrete deck surface area volition exist a unmarried 3" pipe that runs from the ix" basin to the belch point.

STEP 10:
Choose the discharge stop device.

In our example, the ends of the drainage pipes will be cutting flush with the street curb so no boosted parts are needed. However, in many cases the drainage piping terminates on the property and information technology is best to close it off with a grate or a pop-upwards relief valve to forbid droppings or rodents from entering. This popular-upwardly relief valve sits flush with the surrounding surface area and just pops upwardly to allow excess h2o to discharge when the drainage pipe is full.

APPENDIX

Drainage Pipage

In that location are three common types of drainage pipe to apply.

Corrugated Pipage is flexible and typically can make directional changes without the demand for fittings. The advantages of this type of pipe are its flexibility and its ease of installation. The disadvantages are that it is hard to clean out (because of the corrugations), the connections are not very watertight and that the trench bed has to be very carefully sloped.
Sewer and Drain Pipage is a thin walled PVC pipe. This pipage needs Sewer and Bleed hub fittings to make directional changes and joins. Because of its smooth wall, information technology is easier to make clean and the trench bed slope and smoothness is less critical as this pipage volition somewhat compensate for peaks and valleys.
Triple Wall Piping is similar to the higher up merely has a heavier wall and is thus sturdier. It also requires Sewer and Drain hub fittings to make directional changes. Because of its rigidity, the trench bed gradient and smoothness is even less disquisitional than with the Sewer and Drain piping described above.

Fittings

At that place are 2 common types of fittings that can be used.

Sewer and Bleed PVC hub fittings are used to couple the drainage piping and change directions. The most popular and readily bachelor 3″ and four″ fittings are straight couplers, 90 degree, 45 degree and 22.5 caste elbows, straight and germ-free tees, 45 caste wyes and terminate caps. These fittings are solvent welded onto the pipe.
Single Wall corrugated fittings are used to couple the drainage pipe and change directions. The most popular and readily bachelor fittings are straight couplers, 90 degree elbows, 45 degree wyes, tees and end caps. These fittings snap straight onto the drainage pipage.