Reduce Water Waste in the Home with a Reverse Osmosis System

Clint Elston
Wednesday, 3rd August 2016

How to create a safe reverse osmosis system in the home to prevent water waste.

I would like to share an experiment I recently finished on a house in Minnesota; that of separating the potable water according to the varying quality needs of specific plumbing fixtures, e.g., all bathroom faucets and showerheads and all of the kitchen faucets, the dishwasher, washing machine and refrigerator require a much higher quality of water than is needed for flushing the toilet.

The common definition of branch plumbing is one cold water plumbing line and one hot water plumbing line being supplied with the same water from one potable water source and then that water flows to each specific fixture with no return. Usually those lines are 3/4in and then are reduced down to 1/2in.

The more recent method of plumbing to supply potable water more effectively uses manifolds with individual lines and valves connecting to each fixture. An even better idea is to add a return manifold and to insulate the hot water supply and return lines from each hot water fixture. Then by installing a low-wattage, continuously operating circulation pump, the hot water piping will provide 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 in losing all of that first wasted hot water in the shower or sinks waiting for it to warm up. 

This additional pipe and pump does require a very small amount of financial upfront investment, but it eliminates the need of buying an expensive ‘On Demand’ hot water heater, which usually fails from the elements being in contact with natural water minerals. 

That same circulation pumping system, also installed on the cold water supply line, prevents stagnation of the water and the potential growth of bacteria by recirculating the cold water on a timer and adding more ozone.

For example, the toilet, which, according to the EPA, consumes at least 40% of the household total water requirements, does need to be filtered and disinfected for those times when the household dog drinks out of the toilet or the young children use the toilet to float their boats, but that specific fixture does not need to contain super-high, mineral-free drinking quality water.

Reverse Osmosis System (RO)

With a bunch of recycled plumbing parts, I installed a small RO system in a single family home where water is supplied by the city. The city water is chlorinated and very hard (500 TDS) and has the standard city 50 psi water pressure.

I used a small 4-stage RO filtration unit found at Home Depot. It was a kitchen under-the-counter model with a sediment filter and two carbon filters. I then added three additional RO membrane units capable of producing 400 gallons of permeate water per day (100 gallons of permeate water per day per membrane).

The major difference in my design is that it requires more and larger water storage tanks for the good (permeate) and bad (concentrate) water because of the slow rate of production of this smaller, low-pressure RO system. However, the costs for polyethylene storage and fiberglass pressure tanks are minimal. You can purchase everything online from such suppliers as Good Water Warehouse, for less than $500.

I assembled the 4 multiple low-pressure (50 psi) RO membrane units in parallel. The RO concentrate water is plumbed to a separate pressurized 20-gallon storage tank and then plumbed to the toilet with a separate 1/2in plumbing line. The RO concentrate water is to be utilized solely and specifically for flushing the toilet and/or potentially for irrigation.

That concentrate water pressure tank also has a 1/4in return plumbing line to the beginning of the RO unit. This additional feature provides an overflow protection, which redirects the excess concentrate water back through the entire RO process again instead of discharging any of it as waste. High levels of concentrated minerals and whatever else that was rejected by the RO membrane, stored temporarily, are eventually eliminated with each flush of the toilet. 

The toilet water is still safe as it is supplied by the city and then it additionally passes through the sediment and carbon filters before being stored in the concentrate toilet flushing tank. It just has higher levels of minerals, because it is the RO concentrate.

The remaining 50% 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. It has an ozone venturi pumping injection circulation system to continuously disinfect the water, which totally destroys ALL forms of harmful bacteria and ALL of the protozoa, viruses, etc. Ozone is far superior to chemicals and ultraviolet light for several reasons.

With a separate 30-50 psi pressure-switch-activated water supply pump combined with a separate 20-gallon RO pressurized storage tank, the completed system then provides every household plumbing fixture, (sinks, laundry, showers, baths, dishwasher, refrigerator, etc.) except the toilets, with the highest quality, ozonized, RO permeate water possible.

One often hears, “But reverse osmosis filtration is expensive and environmentally wasteful because it discharges almost 50% of the total amount of treated water (concentrate) to get the remaining 50% of good (permeate) drinking quality water.”

The public is right! However; by simply running new 1/2in plumbing lines to the toilets alone, that potentially wasted RO concentrate water is redirected to a pressurized storage tank to await redistribution and supply to the toilets. Traditional, standard RO-supplied systems discharge at least 25-50% of the water processed as unusable and since the toilet consumes at least 40% of the water in a conventional household, why not make these simple plumbing changes to eliminate the waste?

The public’s objections are removed, a conventional water softener is unnecessary because you now have RO water for every household fixture, while knowing that you’ve utilized every drop of water in your house efficiently, effectively and economically with the concentrate being used by the toilets.  

The system’s only energy requirements are supplied with 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 status quo of plumbing! Additional flow meters and pressure gauges can be added to provide all of the information needed for monitoring, maintenance and the replacement of filters and membranes.

This is not science fiction or rocket science. This is just being aware, accepting change and being able to adapt to new technologies and utilize what they have to offer. Usually, almost always, for the better!

About the Author:

Clint Elston has been developing his greywater treatment and potable water recycling systems for the plast 20 years. Previously he spent 13 years in Alaska where he perfected his compost toilet systems and before that was in the US Army. He is a 30% Disabled American Veteran, and longs to move to Costa Rica to offer his experiences and technologies to a country that has no water/sewer infrastructure.

Further resources

Using floating ecosystems to clean waterways

Recycled IBC tanks: storing water and growing vegetables

Capturing rainwater in the city

Watch: Harvesting rainwater in the urban environment

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