[osolemio]

Where I live, rain water harvested water may only be used for toilet flushing, laundry, irrigation of non-edibles, cleaning and so on. And that's it, no showering, dishwasher etc.

I have such a rainwater harvesting system now, which is working fine except ... I produce way more water than I can use by flushing toilets and doing laundry.

I want to expand the use of rain water to as much as I can, apart from drinking and cooking purposes. That means all hot water and all normal taps, as I will keep a few dedicated cold water taps with straight city water.

There are systems to clean water by a series of filters, usually one or more particle filters, then an active carbon filter followed by a UV filter.

I am considering the option of having a pump and a UVC filter installed directly inside the underground rainwater tank, where a small pump runs continuously and exposes the water in the rain water tank to UVC light. The water in the tank is constantly around 40F, there is no sunlight at all, so the level of bacteria growth is an absolute minimum. The technique of having a pump and a UV filter is often used in garden fish ponds to keep water clear and clean.


I think it makes more sense to have the UV light in the rainwater tank, not in the filter in the house, as the cleaning function of the UV filter is pointless all the while there is no flow of water. I realize that since the water exposed to UVC light is returned into the same tank, it is not a 100% guaranteed method, but I am convinced it will keep the level of bacteria to an absolute minimum. The intake for the pump will be from the far end of the rainwater tank, and the outlet just next to where the rainwater system sucks its water from.

The pump and the filter will use less than 30W, but since it will be running year-round, it does create some impact on the electricity use. I will have a solar PV installed this summer, so it will not be the greatest issue though.

Do I still need a UV filter inside the house, downstream of the particle and carbon filter?

Although the water is not going to be used directly for cooking or drinking, I still want to make sure it is free of bacteria, as it will be used for showering (can be inhaled in the steam), in the dishwasher (food/drink will be consumed by the cleaned items).

I need all your expertise in this project, so I can make a system which is not prohibitive in investment and running cost. It must work in the simplest way possible, be reliable and just do its job.

One day, I will stand in the shower, using water harvested from the roof, heated by the sun. I cannot wait, really, but I am not there yet.

Please help me on my way by offering your opinions and ideas.

Thank you.