# How much water comes off my roof when it rains?

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So, how much rainwater can a homeowner expect to collect and store in Texas? Assuming a collection efficiency of about 80 percent, it turns out that this volume is roughly 1,000 gallons for every inch of rainfall that falls on a 2,000 square-foot roof.

## How do you calculate rainwater runoff from a roof?

How Much Rain Water Runs Off Your Roof?

1. Take the dimensions of the footprint of your roof and convert them to inches. (So, a 50′ x 20′ roof is 600″ x 240″.)
2. Multiply the roof dimensions by the number of inches of rainfall. (In this example, 600″ x 240″ x 1″ = 144,000 cubic inches of water.)

## How much rain comes off a roof?

Typically, one rain barrel will fill in just minutes in an average downpour. One inch of rain on a 1000 square foot roof will yield around 600 gallons.

## How many gallons of rain come from roof?

Every square foot of roof space collects . 6 gallons of water in a 1 inch rainfall.

## How much water can I catch off my roof?

Approximately 550 gallons of rainwater can be collected for every 1000 square feet of collection surface per inch of rain. To estimate amount collected in one year, take the square footage of your collection surface, divide by 1000, multiply by 550 and then multiply by the average annual rainfall for your area.

## How do I calculate roof drainage?

Take the roof’s total square footage and divide by the total square footage handled by one drain. The result is the number of drains needed. For example: 50,000 / 4,400 = 11.36; or 12 drains required.

## How do you calculate rainwater discharge?

Storm water Discharge calculations: Using Rational formula i.e. Q=CIA Where Q – is design peak runoff rate m3/hr. I – Rainfall Intensity value in mm/hr. A – Catchment area in Ha.

## How long does it have to rain for 1 inch?

One (1.00) inch of rain – A light moderate rain never reaches this amount, heavy rain for several hours (2-5 hours). There would be deep standing water for long periods of time.

## How fast does a 55 gallon rain barrel fill?

How long does it take to fill my rain barrel? It depends on how much roof area drains into your barrel. The average size roof area that drains into one downspout is 300 sq ft or 30 ft long by 10 ft wide. It takes only 0.3 inches of rainfall to fill one, 55 gal barrel off of 300 sq ft of roof!

## How much does 1 inch of rain raise a lake?

It is about 25mm. Joking aside, an inch of rain is the measure of rainfall that would cause a puddle of water over a given area to be one inch deep.

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## How fast do rain barrels fill up?

It’s common for about 1/8″ inch of rain to fall each hour during a moderate rainstorm. That means that a 500 square foot roof can fill a properly installed 50-gallon rain barrel in about one hour.

## How much is 1 inch of rain in gallons?

One inch of rain falling on 1 acre of ground is equal to about 27,154 gallons and weighs about 113 tons.

## Are rain barrels worth it?

Many arid or drought-prone regions have restrictions on lawn watering, and a rain barrel system can be an excellent way to get around these rules. If water use is expensive, capturing precipitation to use in the household can also be worthwhile. … Considering this, a 4,000-gallon system might cost \$15,000.

## How much water is an inch of rain?

Rainfall amount is described as the depth of water reaching the ground, typically in inches or millimeters (25 mm equals one inch). An inch of rain is exactly that, water that is one inch deep. One inch of rainfall equals 4.7 gallons of water per square yard or 22,650 gallons of water per acre!

## What happens when rain barrel is full?

When the rain barrel is full, the diverter shuts off, and the rainwater will simply flow through the gutter like it normally would. … But when there is a heavy rainfall, many times the rain barrel overflow valve can’t keep up, and excess water can bubble over the top of the barrel rather than out the release valve.

## How do you collect rainwater from your roof?

The rain will collect in gutters that channel the water into downspouts and then into some sort of storage vessel. Rainwater collection systems can be as simple as collecting rain in a rain barrel or as elaborate as harvesting rainwater into large cisterns to supply your entire household demand.

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