Reverse Osmosis Without Wastewater
An Inexpensive Plumbing Solution
by Clint Elston

I wanted reverse osmosis (RO) water in my single-family home in Minnesota, but I didn’t want to pay the big money for a whole-house system.

I also realized that during the purifying process, an R.O. system discards 25 to 50 percent of the source water down the drain.

So it started me thinking how to get reverse osmosis without wastewater.

Since I worked in construction all my life, I was aware that existing “branch” plumbing piping designs send 40 percent of all of my good household water to the toilet to be consumed by the 1.6 gallons of water each time it was flushed. 

How to Reuse the Wastewater

Then I questioned why all the water in my house needed to be of R.O. purity when we’re just going to turn around and flush 40 percent more of that good water down the toilet.  

Of course, the kitchen and bath faucets, the dishwasher, washing machine and refrigerator require a much higher quality of water than would be needed to flush the toilet. 

And the toilet water still needs to be filtered and disinfected for those times when the household dog drinks out of the toilet or a child floats its rubber ducky in it, but that specific fixture doesn’t need to be using super-high, mineral-free drinking quality water. 

The Plumbing Solution

That’s when it dawned on me that I could solve both problems with a few minor plumbing changes.

The R.O.’s bad (concentrate) rejected water wouldn’t have to be wasted, if we could send it to the toilets for flushing instead.

So with a bunch of recycled plumbing parts, I installed a small R.O. system in my single-family home where heavily chlorinated water is supplied by the city, with a 500 TDS, utilizing the standard city 50 psi water pressure.  

This small 4-stage, kitchen under-counter R.O. filtration unit from Home Depot had a sediment filter and two carbon filters.  

I then added three additional R.O. membrane units capable of producing 400 gallons of permeate good water per day (100 gallons of permeate water per day per membrane). 

Inexpensive Design

The major difference in my design is that it requires larger water storage tanks and more of them for both the good (permeate) and bad (concentrate) water because of the slow rate of production of this smaller, low-pressure R.O. system. 

However, the costs for polyethylene storage and fiberglass pressure tanks are minimal compared to a whole-house R.O. system.  You can purchase everything online from suppliers such as Good Water Warehouse, for less than $500. 

The R.O. concentrate water is plumbed to a separate pressurized 20-gallon storage tank and then plumbed to the toilet with a separate one-half-inch plumbing line.  

It can be utilized solely and specifically for flushing the toilet and/or potentially for irrigation. 

That bad (concentrate) water pressure tank also has a one-quarter-inch return plumbing line back to the beginning of the R.O. unit.  

This additional feature provides an overflow protection, which redirects the excess bad (concentrate) water back through the entire R.O. process again instead of discharging any of it as waste.  

Water for Toilet Flushing

High levels of concentrated minerals and whatever else rejected by the R.O. membrane is stored temporarily and eventually eliminated with each flush of the toilet.

The toilet water is still safe as it was originally supplied by the city and has even passed through the sediment and carbon filters before being stored in the concentrate toilet flushing tank.  

The toilet water just has higher levels of minerals, because of it being the R.O. concentrate.

Ozonized R.O. Water for Faucets

The remaining 50 percent good (permeate) water is separately plumbed to a large unpressurized storage tank of at least several hundred gallons, depending upon the number of membranes needed in accordance with the installation’s design.  

An ozone venturi injection circulation system then pumps ozone into the line to continuously disinfect the water, and destroy all forms of harmful bacteria, protozoa, and viruses, etc.

The public is quickly becoming aware that ozone is far superior to the use of chemicals and ultraviolet light to purify water. 

When a separate 30–50 psi, pressure-switch-activated water-supply pump is combined with a separate 20-gallon R.O. pressurized storage tank connected to the large ozone water storage tank, the completed system then provides all the household plumbing fixtures, except for the toilets, with the highest quality, ozonized R.O. permeate water possible.

Energy Requirements

The system’s only energy requirements are supplied by the standard 50 psi water supplied by the city and/or well with a pump.  

It is inexpensive to install and operate, and only involves a change in the plumbing!  

Additional flow meters and pressure gauges can be added to provide all the information needed for monitoring, maintaining, and the replacing filters and membranes.   

To further increase my home’s energy efficiency, I used plumbing manifolds with individual lines and valves connected to each fixture, then added a return manifold, and insulated the hot water supply and return lines from each hot-water fixture. 

Adding a Circulation Pump

By installing a low-wattage, continuously operating circulation pump, the hot water piping provides instant hot water with the turn of the knob at every hot water fixture.  

The cost of the electricity for the circulating pump is less expensive than the cost expended waiting for the water to warm up and you do not lose the water!

With separate plumbing lines sending variable water qualities to different locations, the new circulating system supplies instant potable hot water to every hot water fixture. 

This means not having to buy an expensive “on demand” hot-water heater, which unfortunately fails anyway from the elements coming into contact with natural water minerals.  

An additional asset is that the same circulation pumping system can also be installed on the cold water supply line, which prevents stagnation of the water and the potential growth of bacteria by recirculating the cold water on a timer and adding more ozone during the circulation.

Summary

Yes, it is possible to have reverse osmosis without wastewater. This type of installation does require a little imagination, carpentry and plumbing skills. 

It also provides a paradigm shift in designing plumbing water-supply systems as we become more aware of the valuable water we drink, bathe in, and use for hygiene. 

About the Author

Clint Elston is a wastewater and energy consultant and the inventor of proven decentralized, onsite composting toilet, greywater treatment and recycling systems. Having fought the predisposed engineering, governmental regulatory and academic communities throughout the entire United States, Clint plans to move to Costa Rica, where he can offer his experiences and technologies to a country and region of the world that has no water and/or sewer infrastructures.  

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