Rainwater collection down under

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  • Fri, Nov 29, 2019 - 04:20pm



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    Rainwater collection down under

We’ve been collecting and using rainwater for all our domestic consumption for about 20 years now.  It’s very common in rural New Zealand for roof water to supply all domestic consumption including drinking.  We have two 5000 gallon tanks that collect rainwater from the downspouts on our house and garage.  The tanks have floating water pickups in them to take water from the top of the water column rather than the base of the tank. From the tank there are large 20 micron and 2 micron filters in series after the pressure pump.  From the filters the water passes through a UV filter before going to the house.  Our fridge/ice maker has an additional small bacterial filter inline.  We should have a first flush diverter installed to dump the first 5 gallons of water which is typically the most polluted but somehow that didn’t get installed in our system.

Some sources of harvesting ideas are here….



Note at the Marley website page there is a downloadable rain harvesting brochure with lots of good information.

As for roof materials, best practice in NZ is to collect water from painted metal roofs (corrugated or standing seam are typical here).  We’ve been collecting from an asphalt roof and I did have concerns about chemical leaching.  I had the roof/tank water tested about 10 years ago and for the chemicals they test for (arsenic, lead and other heavy metals), the values were very low – zero.  This was after ten years of using the roof though so you would expect if leaching was happening it would have decreased with age.  Ironically, in some areas of New Zealand, over use of fertilizer has lead to aquifer pollution and the town supplies of drinking water have higher contamination levels than you typically find from roof water collection.

I’m a huge fan of roof water collection and though we’re lucky to have a well on the property we only use it to top up the tanks over the dry mid-summer months for either the house or stock troughs.