Saving money with rainwater 💦 harvesting from your commercial building

✔️Step 1: Find the historic rainfall levels in your area from Met Eireann:

✔️Step 2: Calculate your building’s roof collection area from Google Maps:


Right Click in map, select measure distance, draw a line around the roof and it will calculate the Roof Area in m²

✔️Step 3: Calculate your potential Annual rainwater yield:

Annual rainwater yield = P x A x R

P = annual rainfall in mm

A = Roof collection area in m2

R = Roof Co-efficient

Let’s look at an example:

Site Location                                          : Dublin 15

Roof Area                                                : 10,028m²

Roof Co-efficient                                  : 0.8**

Rainfall                                                    : 757.9 mm/ Mean avg. / Year

Weather Station                                : Dublin Airport Station

Potential Water Savings               : 757.9 x 10,028 x 0.8 = 6,080,177 Lt/Year

Area Potential Rainwater Water Savings: 6,080,560.45 Litres/Year or 6,080m3 /Year

Financial Savings                                 : 6,080m3 x €1.99* = €12,099 / Year!

*Dublin Water Charges: Supply m3: €1.16, Wastewater Services m3: €0.83, Combined m3: €1.99

**typically you should expect to collect 80% of this rainwater each year due to losses in filtering and small rainfalls that do not generate enough runoff

☎️ 📲If you need any further information or help, do not hesitate to contact me

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