RAIN WATER HARVESTING FOR HOUSES

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1 RAIN WATER HARVESTING FOR HOUSES Lessons learned from a domestic installation Andy Cunninghame October 2017t

2 Water Security

3 Drought Risk Areas Western Cape Government 2012 Climate Change and Water Security 3

4 Water consumers Why we need to target single residential households Water use by land-use category 55% of water in the City of Cape Town is consumed by single residential homes The second largest consumers are retail and offices at 12.8% The third largest consumers are flats and complexes at 9,8 % Why target single residential homes for rain water harvesting? As the largest users, reducing their consumption will have the biggest impact. They all have roofs that they own and can utilise for rain water harvesting. Many already have rain water tanks or swimming pools to store rain water. Rain water is easily processed to provide water for domestic purposes. Rain water is relatively pure and does not contain the harmful metals and chemical substances associated with boreholes. The cost is not excessive affordable solution for many residents. City concerns are easily addressed by the City fitting approved non-return valves to homes participating in rain water harvesting NB. Cost to City low in comparison with measures such as desalination. Western Cape Government 2012 Climate Change and Water Security 4

5 Water security Legal issues - City of Cape Town Water By-law 2010 Extract from Paragraph 56: (1) No person may use or permit to be used any water obtained from a source other than the water supply system of the City for domestic purposes. Definition: "domestic purposes" in relation to the supply of water means water supplied for drinking, ablution and culinary purposes excluding toilets and urinals;" Comment: The By-law was drafted at a time when nobody thought the City would face a crisis of the magnitude we now face. The question of the amendment of the By-law has been raised with City officials who responded that the matter is receiving serious consideration. Western Cape Government 2012 Climate Change and Water Security 5

6 Rain water harvesting

7 Rain Water Harvesting How the rainwater is harvested Rainwater sources Typically rainwater is harvested from: Roofs via gutters and downpipes Clean paved surfaces Rainwater capture and processing A mesh screen is required remove leaves and other large particles The mesh screen can be a commercially available leaf catcher The rain water runs by gravity into a storage tank (can be your swimming pool) The rain water is filtered and treated prior to use The filtered and treated rain water is pumped into the existing water reticulation A pump with automatic pressure control is used to maintain water pressure Will there be enough rainwater for all my household needs? The graphs on the following pages provide some answers Western Cape Government 2012 Climate Change and Water Security 7

8 Kilolitres Rain Water Harvesting Rainfall harvesting vs home water consumption of 12 kl per month Sum kl Rain water harvested 209 kl/year kl reservoir Home use at 12 kl/month Sum kl Home use 144 kl/year 50 0 Month 2013 Western Cape Government 2012 Climate Change and Water Security 8

9 Kilolitres Rain Water Harvesting Rainfall harvesting vs home water consumption of 12 kl per month Sum kl Rain water harvested 116 kl/year Home use at 12 kl/month Home use 144 kl/year kl reservoir Sum kl 20 0 Month 2016 Western Cape Government 2012 Climate Change and Water Security 9

10 Kilolitres Rain Water Harvesting Rainfall harvesting vs home water consumption of 6 kl per month 2016 Rain water harvested 116 kl/year Sum kl Home use at 6 kl/month kl reservoir Home use 72 kl/year 40 Sum kl 20 0 Month 2016 Western Cape Government 2012 Climate Change and Water Security 10

11 Rain Water Harvesting Swimming pool as reservoir Downpipes from the roof are extended using removable 110 mm PVC water pipes Western Cape Government 2012 Climate Change and Water Security 11

12 Rain Water Harvesting Transfer pump from pool to treated water tank (via filtration) Western Cape Government 2012 Climate Change and Water Security 12

13 Rain Water Harvesting Filtration, storage and pumping to house Filtration Treated water tank From pool Automatic pressure pump To house Western Cape Government 2012 Climate Change and Water Security 13

14 Rain Water Harvesting Connection to house plumbing Spring loaded non-return valve on municipal supply Pressure reduced supply to house (2 bar) Note: In addition to the Spring loaded non-return valve on municipal supply, stop cocks must be fitted to the two sources of supply. When using the rain water supply the stop cock on the municipal supply must be firmly closed. Similarly, when using municipal water the stop cock on the rainwater supply must be firmly closed. From treated water tank This is essential to protect the municipal supply from possible contamination and to protect the rainwater system from high municipal water pressure. Western Cape Government 2012 Climate Change and Water Security 14

15 Rain Water Harvesting Lessons learned Filtration The minimum filtration requirements is: A 5 micron filter (note: if Giardia or Cryptosporidium are present use a 1 micron absolute filter) An activated carbon filter Rainwater treatment If using a swimming pool for rain water, keep the pool clean and chlorinated. Slug dose the pool with chlorine after each rainfall. Reduce the pool water chlorine to 1 ppm (same ph as municipal water) before transfer to the clean water tank i.e. remove the pool cover and let the sun reduce the chlorine before transferring to the clean water tank. If rain water is stored in a tank, the tank must store water in the dark. If rain water goes directly from the roof to a tank, the water must be sterilised using an ultra-violet light when pumped into the house water reticulation. Water supplied to the house must have a ph of 8 to protect the copper pipes. The ph can be raised from 7 to 8 by adding 2 cups of bicarb per 1000 litres of water Western Cape Government 2012 Climate Change and Water Security 15

16 Rain Water Harvesting So what did the domestic installation cost? Item Cost 1500 litre Jo-Jo tank R2360 Transfer pump (530 watt motor) R790 Duplex filter housing R540 5 micron filter cartridge R20 Activated carbon filter R60 Pressure pump (375 watt) with control unit R meter of 15mm polycop pipe R160 Sundry pipe fittings, valves and pipes R900 Electrical extension lead, box, etc R230 TOTAL R6330 Western Cape Government 2012 Climate Change and Water Security 16

17 Rain Water Harvesting Rain water sterilisation and filtration homes without a swimming pool for storage The photograph shows a rain water purification installation suitable for a home where the water is harvested directly from the roof into storage tanks. The installation is designed to produce potable water. The cost of the UV lamp is ±R (supply only). UV light Filtration Western Cape Government 2012 Climate Change and Water Security 17

18 Thank you

19 Contact Us Andy Cunninghame Departmental Energy Champion Tel: Fax: