Fresh Water, Grey Water, Sustainability

Water Filtration – Reverse Osmosis

Since it is impossible to know where we will be going, or what the drinking water will be like; we will be installing the Hydro-Logic Stealth-RO150 w/ Upgraded KD. We do not anticipate this being a “whole house” install due to the large amount of grey water created by RO Filters; instead this will be a “point of use” install for the Kitchen.

RO_Filter
Hydro-Logic Stealth-RO150 w/ Upgraded KDF

Filtration is the process of removing contaminants from a substance, in our case water. There are 3 Primary Levels of Filtration:

  • Micro – Filter pore size 0.5 – 5 microns; removes Protozoa & Bacteria such as Giardia and Salmonella, but not Viruses and Chemicals
  • Ultra – Filter pore size 0.001 – 0.5 microns; removes Protozoa, Bacteria, & some viruses, and low amounts  of Chemicals
  • Nano – Filter pore size 0.008 – 0.01 microns; removes Protozoa, Bacteria, Viruses, & moderate amounts of Chemicals
  • Reverse Osmosis Systems – Filter pore size 0.0001; removes Protozoa, Bacteria, Viruses, AND Common Chemical Contaminants

*This, and more information can be found at the Center for Disease Control website, found here.

The Stealth-RO150 is capable of producing on average, 150 Gallons of pure, low PPM water each day. We don’t plan on using that much water every day, but it is nice to know that our filters will go a long way! Instead, we will be using a small (~4 gallons) holding tank to store our RO water for cooking and drinking needs. At the available rate of 150 gallons per day, our modest 4 gallon tank can be filled, from empty, in less than an hour.

under-sink-ro-unit-installation1
Typical Residential “under sink” install of RO Filter (right) & Holding Tank (left)

Theres another point to consider, RO Filters usually need about 60psi of water pressure to operate properly, with the absolute minimum ~40psi. Our planed water pump delivers 55psi of pressure, but does not kick back on as the pressure decreases, until the pressure at the pump drops below 25psi. I’m not 100% this is going to work without issue; but is just something we’ll have to wait and see what happens in the real world.

RO filters are known to be inherently wasteful. While most RO Filters create waste at the rate of 3:1, or 3 Gallons Waste to 1 Gallon Pure Water; the Stealth-RO150 comes with not only a 2:1 adapter, but ALSO a 1:1 adapter. The 1:1 capability is huge for us, and one of the main reasons that we will be using this filter on the OffGridSkoolie. Fortunately, the waste water created will go on as our Gray Water, and will be used to flush our toilets, amongst other things.

Hydro-Logic also sells a Membrane Flush Kit, which is essentially a backwash kit for the RO Filter. Like a backwash on a pool filter, the Membrane Flush Kit reverses the flow of water into the RO Filter, cleaning and remove sediments and debris from the membranes of the filter. Cleaning the membranes on your RO Filter will reduce the build-up of sediments on the filters membrane, thus extending the life of the filters. While boondocking, we likely wont use this feature; instead, we’ll wait until we can hook up, where water isn’t as much of a concern.

 

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