There’s no drinking from the hose in our back concrete.

My grandparents had rain barrels: metal barrels that collected water off the roof to be used – I don’t know where they used it, maybe in laundry.

But in drought-ridden Brisbane, where they have a 200-year flood every 20 years, these fancy collection tanks (right) are standard.

Water is collected from the roof and stored in these tanks, and used through a separate plumbing system for toilets, dishwashers, laundry and watering with a hose.

As I water my collection of fruit trees and plants, I wonder about E. coli and other levels of potentially dangerous bacteria that accumulate in these tanks, and are then dispersed onto growing plants that may be eaten raw.

I don’t know the answers.

Some researchers in South Africa gave it a shot. Abstract below.

The possible health risks associated with the consumption of harvested rainwater remains one of the major obstacles hampering its large-scale implementation in water limited countries such as South Africa. Rainwater tank samples collected on eight occasions during the low- and high-rainfall periods (March to August 2012) in Kleinmond, South Africa, were monitored for the presence of virulence genes associated with Escherichia coli. The identity of presumptive E. coli isolates in rainwater samples collected from 10 domestic rainwater harvesting (DRWH) tanks throughout the sampling period was confirmed through universal 16S rRNA PCR with subsequent sequencing and phylogenetic analysis. Species-specific primers were also used to routinely screen for the virulent genes, aggR, stx, eae, and ipaH found in enteroaggregative E. coli (EAEC), enterohemorrhagic E. coli (EHEC), enteropathogenic E. coli (EPEC), and enteroinvasive E. coli, respectively, in the rainwater samples. Of the 92 E. coli strains isolated from the rainwater using culture based techniques, 6% were presumptively positively identified as E. coli O157:H7 using 16S rRNA. Furthermore, virulent pathogenic E. coli genes were detected in 3% (EPEC and EHEC) and 16% (EAEC) of the 80 rainwater samples collected during the sampling period from the 10 DRWH tanks. This study thus contributes valuable information to the limited data available regarding the ongoing prevalence of virulent pathotypes of E. coli in harvested rainwater during a longitudinal study in a high-population-density, periurban setting.