If you have an option to invest in an equipment, you should purchase the rain water barrel. There are large storage tanks, which can be installed above the roof (for year around supply). Or another option is, simply set the barrel under the roof or gutter to collect the water, and use it for your garden, or for your toilet flushes.
There are several practical ways of recycling and reusing domestic waste water, but you need to get creative with your thoughts and take measures to implement it in daily life. For industrial uses, you can always install industrial wastewater filtration systems sourced from a reliable industrial wastewater recycling system distributor.