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The FAS Drainage Standard

The FAS Drainage Standard is the five rules Florida Aqua Solutions (FAS) designs drainage to. A system is sized to a 25-year storm from NOAA Atlas 14, laid on fall measured on site of at least 1%, and built with pipe chosen for the fall the ground actually has. The work is done under Florida licence CBC1269202 and checked in the field and in Water MRI before anything goes in the ground.

  1. Sized to a 25-year storm from NOAA Atlas 14.
  2. Fall measured on site before design: at least 1%, about 1/8 inch per foot, from inlet to outlet.
  3. Pipe chosen for the fall the ground actually has.
  4. Florida licence CBC1269202, with civil engineers on projects that need extra assurance.
  5. Field checks plus Water MRI before anything goes in the ground.
Book my $89 drainage assessment or call (407) 490-0441

Nothing is charged when you request.

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The standard, point by point

Five rules, each with a number you can check.

Most failed systems we are called to were built on shortcuts. Here is what we do instead, why, and where each number comes from.

Sized to a 25-year storm, from NOAA Atlas 14.

A 25-year storm is rain heavy enough to come about once every 25 years on average, about a 4% chance in any year. A system sized for everyday rain copes with light and medium storms and is overwhelmed by the big one. So we size to the big one, and we take the rain from the federal record, not from a guess.

The number

In Orlando a 25-year storm is 7.53 inches of rain in 24 hours and 3.34 inches in one hour.

Source: NOAA Atlas 14, Precipitation Frequency Data Server. What is a 25-year storm in Central Florida?

Fall measured on site before design: at least 1% from inlet to outlet.

Fall is how far the pipe drops along its run. Pipe laid by eye has uneven fall. Low spots hold water and silt until the line clogs. So we measure the fall the ground has before we design anything.

The number

We design for at least 1% of fall, about 1/8 inch per foot, from inlet to outlet. That is 1 foot of drop per 100 feet of pipe.

Source: the FAS design standard. At 1% a 4-inch smooth-wall pipe runs at about 2.4 to 3.2 feet per second, by Manning's equation with the ADS and FDOT roughness figures.

Pipe chosen for the fall the ground actually has.

Corrugated pipe has a ribbed wall that slows the water. On ground too flat for it, the water is too slow to carry silt out, and the line clogs from the low spots. Smooth-wall pipe moves the same water on far less fall. So the ground decides the pipe.

The number

A 4-inch corrugated line needs about 2% of fall to carry silt out. Smooth-wall pipe does the same job on about a quarter to a third of that.

Source: calculated with Manning's equation from the roughness figures in the ADS Drainage Handbook and the FDOT Drainage Manual. How much slope does a French drain need?

Florida licence CBC1269202, with civil engineers on projects that need extra assurance.

A licence number is a fact you can ask for and write down. Ours is on every page of this site. In our own words: “We're a Florida-licensed Certified Building Contractor, and we work with civil engineers on many of our projects that need extra assurance.”

The number

Florida licence CBC1269202.

Licensing body: Florida Department of Business and Professional Regulation.

Field checks plus Water MRI before anything goes in the ground.

Water MRI is our own storm software. It runs a 25-year storm across a model of the property, from the roof to the street, and shows where water stands, how deep and for how long. FAS reviews the result. When we need more accuracy, we check the ground, drains and outlets in person.

The labels

Every Water MRI result carries two labels: Visualization and A model, not a guarantee.

A field assessment takes 1½–2 hours when it is needed, with no second fee.

Before you hire anyone

Three questions to ask any drainage contractor

Each one has an answer you can write down. Here are ours.

  1. 01What storm is it sized for?The FAS answer: a 25-year storm from NOAA Atlas 14. In Orlando that is 7.53 inches of rain in 24 hours.
  2. 02What fall did you measure?The FAS answer: we measure it on site before design, and we design for at least 1%, about 1/8 inch per foot, from inlet to outlet.
  3. 03What is your licence number?The FAS answer: Florida licence CBC1269202.
5.042 reviews on GoogleFlorida licence CBC1269202

The $89 assessment shows where the water comes from and where it can go.

Book my $89 drainage assessment

The offer

$89

Drainage assessment of your property.
Credited toward your project.

  • A Water MRI flood simulation: your property modelled, from the roof to the street
  • A 25-year storm run across it: where water stands, how deep, for how long
  • Reviewed by FAS, with written recommendations
  • A field assessment when we need more accuracy, with no second fee
  • Credited in full toward a resulting FAS projectOnce, within the project's initial one-third deposit.

How payment works. Requesting is free. FAS confirms the details with you first, then collects the $89.

Book my $89 drainage assessment

Nothing is charged when you request. Water MRI is a visualization. A model, not a guarantee.

Questions

About the standard.

Talk it through

(407) 490-0441

Tell us where the water collects and what it has reached. We will tell you what the $89 assessment will show.

Book my $89 drainage assessment
What is the FAS Drainage Standard?

It is the five rules Florida Aqua Solutions (FAS) designs drainage to. One: sized to a 25-year storm from NOAA Atlas 14. Two: fall measured on site before design, at least 1%, about 1/8 inch per foot, from inlet to outlet. Three: pipe chosen for the fall the ground actually has. Four: Florida licence CBC1269202, with civil engineers on projects that need extra assurance. Five: field checks plus Water MRI before anything goes in the ground.

What is a 25-year storm in Orlando?

A 25-year storm is rain heavy enough to come about once every 25 years on average, about a 4% chance in any year. In Orlando that is 7.53 inches of rain in 24 hours and 3.34 inches in one hour, from NOAA Atlas 14.

How much fall does a drain pipe need?

FAS designs for at least 1% of fall, about 1/8 inch per foot, from inlet to outlet. A 4-inch corrugated line needs about 2% of fall to carry silt out. Smooth-wall pipe does the same job on about a quarter to a third of that.

What should I ask a drainage contractor before I hire one?

Ask three questions: what storm is it sized for, what fall did you measure, and what is your licence number. The FAS answers are a 25-year storm from NOAA Atlas 14, fall measured on site before design with at least 1% from inlet to outlet, and Florida licence CBC1269202.

Sources

Where the numbers come from

  1. NOAA Atlas 14, Volume 9, Version 2 (Southeastern States), Precipitation Frequency Data Server.Point estimate for Orlando (28.5383 N, 81.3792 W), partial-duration series. 25-year rain: 7.53 inches in 24 hours, 3.34 inches in one hour. Read on 2026-11-10.https://hdsc.nws.noaa.gov/pfds/
  2. ADS Drainage Handbook, Hydraulics section.Table 3-1, pipe roughness (Manning n): single-wall corrugated pipe 3 to 6 inches 0.015; smooth-wall sewer and drain pipe 3 to 6 inches 0.009.https://assets.adspipe.com/m/4f6d410de4cd761f/original/Hydraulics-Section-of-Drainage-Handbook.pdf
  3. FDOT Drainage Manual, January 2021.Section 3.6.4, pipe roughness (Manning n): single-wall polyethylene 0.024; smooth-interior PVC 0.012. Section 3.6.1, minimum water speed of 2.5 feet per second for a storm drain flowing full.https://fdotwww.blob.core.windows.net/sitefinity/docs/default-source/roadway/drainage/files/drainagemanual2021.pdf

Pipe-fall figures on this page are calculations from these published roughness figures. They are general guidance, not a design for your property.

Put the water in its place.

Water that stays after every storm keeps working on your foundation, your slab and your walls. Fix it in the dry months, before next summer's rains.

$89 drainage assessment25-year stormField visit when neededCredited toward your projectNothing charged when you request
Book my $89 drainage assessment or call (407) 490-0441

Nothing is charged when you request.