Contents

- 1 How do you calculate rainwater collection on a roof?
- 2 Is the process of collecting rain water from roof tops?
- 3 Is collecting rainwater illegal in UK?
- 4 How do you calculate rainwater harvesting potential?
- 5 How many downpipes do you need for a roof?
- 6 How do I calculate roof drainage?
- 7 What is the roof top rainwater harvesting method?
- 8 Which is the first state in India to make rooftop rainwater harvesting compulsory to all the houses?
- 9 What are the two main techniques of rainwater harvesting?
- 10 Is rainwater safe to drink UK?
- 11 Why is rainwater illegal?
- 12 Do you need to filter rainwater?
- 13 How is rain water calculated?
- 14 What is the formula of rainwater?
- 15 How is rain fall calculation?

## How do you calculate rainwater collection on a roof?

Roughly speaking, 1 millimetre of rain over 1 square metre of **roof** equals 1 litre of water. This capacity can be calculated using the following formula: Annual **rainfall** (in millimetres) x **Roof** surface area (in square metres) = **Roof catchment** capacity.

## Is the process of collecting rain water from roof tops?

**Rain water harvesting is the process of collecting rain water from roof tops** and directing it to an appropriate location and storing if for future use. On an average, one spell of **rain** for two hours is enough to save 8,000 litres of **water**.

## Is collecting rainwater illegal in UK?

Is it legal to **collect** and use **rainwater** in the **UK**? So a homeowner is deemed not to own the **rainwater** that falls on their property and it must not be harvested. The **rainwater** belongs to the owners of nearby water rights in the expectation that the **rainwater** will eventually make its way onto their groundwater supplies.

## How do you calculate rainwater harvesting potential?

Rooftop RWH **potential** is estimated by multiplying the average annual **rainfall**, roof area and runoff coefficient. Runoff coefficient of the concrete roof is considered in the **calculation** which typically varies from 0.70-0.80.

## 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 47m^{2}. 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.

## 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.

## What is the roof top rainwater harvesting method?

**Rooftop Rain Water Harvesting** is the **technique** through which **rain water** is captured from the **roof** catchments and stored in reservoirs. **Harvested rain water** can be stored in sub-surface ground water reservoir by adopting artificial recharge **techniques** to meet the household needs through storage in tanks.

## Which is the first state in India to make rooftop rainwater harvesting compulsory to all the houses?

**Tamil Nadu** was the first state to make rainwater harvesting compulsory for every building to avoid groundwater depletion. The project was launched in 2001 and has been implemented in all rural areas of **Tamil Nadu**.

## What are the two main techniques of rainwater harvesting?

Broadly there are **two** ways of **harvesting rainwater**, namely; surface runoff **harvesting** and rooftop **rainwater harvesting**. **Rainwater harvesting** is the collection and storage of rain for reuse on-site, rather than allowing it to run off.

## Is rainwater safe to drink UK?

Can I use **rainwater** for potable purposes such as **drinking** and washing? Within a normal system, **rainwater** is classed as non-potable or non-**drinking** water by **UK** water regulations. This means it cannot be used for applications where there is human contact (such as **drinking**, bathing and cooking).

## Why is rainwater illegal?

Most states allow people to harvest **rainwater** on their residential and/or commercial properties for non-drinking purposes, such as watering the lawn. But for your safety, there may be strict rules against harvesting water for drinking, as **rainwater** can contain harmful substances, such as animal feces, E.

## Do you need to filter rainwater?

Water **filters should** not be **necessary** to maintain microbial, chemical or physical quality of **rainwater** if catchments and tanks are well maintained. **Rainwater** supplies may **need** to be filtered to ensure effective UV treatment. UV treatment **does** not remove chemicals from water. UV systems will require a power supply.

## How is rain water calculated?

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 can collect.

## What is the formula of rainwater?

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 is rain fall calculation?

**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.