SIRA is using POLi Payments to facilitate bank transfers for payments for water purchases.
You can read the full security statement here.
"The proxy service means that the customers are simply accessing their original bank site via the POLi servers". Connections are secure and data is encrypted (SSL technology). Accessing your online banking service via POLi is just as secure and safe as accessing that service the normal way. The difference is that SIRA is able to significantly reduce admin overheads with the service POLi provides.
SIRA asks you to consider the following:
If, after reading this, you are still not confident using the service, we ask you to make your payment by credit card.
Image taken from https://www.polipayments.com on 15 March 2019