How Much Water Is In A Roof?

How do you calculate rainwater collection on a roof?

This capacity can be calculated using the following formula: Annual rainfall (in millimetres) x Roof surface area (in square metres) = Roof catchment capacity.

This is an important figure to understand so you can design a Rain Harvesting system and choose a tank size that will meet your water volume requirements..

Can you drink rainwater from roof?

While useful for many things, rainwater is not as pure as you might think, so you can’t assume it’s safe to drink. Rain can wash different types of contaminants into the water you collect (for example, bird poop on your roof could end up in your water barrel or tank).

How do you calculate rainfall per area?

Here’s what you’ll need to do:Measure the diameter of the bucket at the level of the rain. … Measure the diameter of the bucket at the bottom in the same way.Calculate the average of the two diameters.Divide by two to find the average radius.Find the average volume of rain = Depth x radius x radius x 3.14.More items…

How long does it take to fill a rainwater tank?

An average 4 bedroom house has a roof surface area of approx. 200 square metres. So, if you have an average 3 bedroom house and a 3000L tank, it would take 20mm of rain to fill your tank. On average each of us uses 147 litres of water per day.

How do I calculate how much water is in my roof?

How Much Rain Water Runs Off Your Roof?Take the dimensions of the footprint of your roof and convert them to inches. (So, a 50′ x 20′ roof is 600″ x 240″.)Multiply the roof dimensions by the number of inches of rainfall. … Divide by 231 to get the number of gallons (because 1 gallon = 231 cubic inches).

How much water runs off a roof?

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

How do I calculate rainwater pipe size?

For calculation we take the following formula: mean annual rainfall in mm x area in m² x runoff factor = collected rainwater in litres. In our example this means: 450 x 120 x 0.9 = 48 600 litres.

How much rainwater do I need to collect?

To calculate how much rainwater can be harvested, multiply your rainfall (mm) by your roof surface area (m2) being used to catch rainwater. The resulting number represents how many litres of water you can expect to collect.

How many downpipes do you need for a roof?

From Figure 3.5 (A) in AS/NZS 3500.3, the maximum catchment per downpipe is 47m2. To calculate the minimum number of downpipes, divide the roof catchment area by the allowable maximum catchment per downpipe. To calculate the average catchment per downpipe, divide the roof catchment area by the number of downpipes.