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To begin with, a reverse osmosis system squeezes water through a membrane that lets water through, but not much else.
As the contaminants being filtered out build up they must be flushed away. Typically it requires from 3 gallons to 15 gallons of contaminated water to be flushed down the drain for each one gallon of purified water produced.
Obviously this is not very good for water conservation.
Watts has come up with a way of recycling the contaminated waste water thus eliminating the water wasting aspect of a reverse osmosis system. With the new system no water gets run down the drain.
The Watts website claims their patented ZRO-4 Reverse Osmosis System is the first ever that does not waste water. Instead of running the contaminated water down the drain like other RO systems, it pumps the contaminated water into the water heater.
The presumption I assume is that itís ok for the nasty stuff you take out of your drinking water is ok to bath in and wash your hands in. It does save water.
In order to accomplish moving the waste water from the RO unit into the water heater a small pump is connected in series with the membrane unit and they are connected to the hot and cold water supply lines. A pressure switch is used to activate the pump when the pressure in the storage tank drops, and the contaminated water is then pumped into the hot water pipe on the way to the water heater.
The instructions say to locate the ZRO-4 RO system at least 25 feet from the water heater. I wish they would tell us why. What happens if it is closer to the water heater? Is it an energy related thing? Is it to keep the contaminated water in the piping, hopefully to be purged when somebody draws hot water and thus not end up stored in a hot tank? I would really like to know.
Another question I have... does it work with a tankless water heater? Still need to be 25 feet away?
Hot water circulating and hot water demand systems that pump water from the water heater to purge the cooled off hot water in the pipes, or that circulate warm water for instant hot water purposes can interact with the Zero Waste Reverse Osmosis System. Since the pump for the circulating or demand system creates a negative pressure on the hot water pipe and a positive pressure on the cold water, the difference in pressure causes water to flow through the membrane unit and pump, just as though the RO pump is running.
The flow of water though the RO system resulting from the operation of the recirc pump can slow down the delivery of hot water to the fixtures. With the warm water circulating systems and the hot water demand systems your cold water pipes can end up with cooled off hot water in them when you use the cold water tap.
Normally itís not a problem since the water is cooled off, but when used with the RO system it will have contaminated water in it. You would need to purge the water from the pipes before using cold water. In my opinion this would be a HUGE inconvenience, and possibly not even effective. I would not recommend using a hot water delivery system that uses the cold water line as a return line.
A solenoid valve is incorporated into the retro-fit version of the zero waste system in series with the pump. I donít know if a demand pump would cause water to flow through the solenoid valve backwards or not. But it might be a viable solution although it has to be tested.
The Watts ZRO-4 reverse osmosis system reduces Arsenic (V), Cysts, Cyrptosporidium, Giardia, Entamoeba and/or Toxoplasm, Barium, Hexavalent, Chromium, Trivalent Chromium, Copper, Lead, Fluoride, Cadmium, Radium 226/228, Selenium, TDS, and Turbidity.
Read about the Watts Premier hot water circulating system