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In the world of water filters, there are many different kinds.
Many water filtration methods work by trapping contaminants and holding them, such as carbon filtration, or inactivating pathogens in the water so that they are no longer dangerous, such as UV purification.
But reverse osmosis works a little differently, and most RO systems come with a drain line. Why is this needed? And do all reverse osmosis systems needs a drain? Let’s find out.
In most cases, yes, a reverse osmosis system needs a drain. That’s because the water contaminants rejected by a reverse osmosis membrane need to be washed away. Otherwise, the membrane would clog in no time.
In other words, reverse osmosis water filtration produces contaminant-laden wastewater which needs to go somewhere!
The exception to the rule is usually a countertop reverse osmosis system model. These often come with a tank that collects the wastewater, which needs to be emptied manually – into a drain!
Some RO systems will also be designed to reroute the wastewater to use it for other purposes, for example, into the hot water lines for washing dishes or they reroute it back to the RO membrane.
A reverse osmosis filtration system needs a drain to carry away the impurities you want out of your water, and not having a drain to take the wastewater defeats that purpose.
Unlike some other forms of water filtration, reverse osmosis filters impurities, but it does not hold the contaminants, and they need to be rinsed away to make sure the RO membrane does not foul or damage prematurely.
While each model and system will vary a little, you can expect the following from a standard under sink reverse osmosis system:
A reverse osmosis system is usually installed under the kitchen sink so that the RO drain line can be easily connected to the sink’s drain pipe.
To connect the RO drain line to the drain pipe in the kitchen, you need to drill a hole in the drain line and attach the drain saddle.
A reverse osmosis drain line is usually ¼ of an inch to ⅜ of an inch in diameter. If you are planning to have your system in a different area, or you are planning to run your waste water to another part of the house, then you may have to replace the drain lines that come with the system with longer ones with the same diameter.
An RO drain line does not require a whole lot of pressure to push the water through, so you can run them pretty far away from the system itself. For example, if you want your wastewater flowing into a wastewater tank outside for gardening or car washing, you probably can do so.
Several components of a reverse osmosis drain system keep it functioning effectively and keep contaminants away from your clean water.
A flow restrictor does exactly what the name suggests. It controls the amount/speed of water that goes down the RO wastewater drain. Without a flow restrictor, way too much water would flow down the drain instead of through the RO membrane.
Flow restrictors will vary in size depending on your RO system’s production/filtration rate. For example, a system that filters 50 gallons of water per day will need a larger flow restrictor than one that filters 25 gallons per day.
This is the device that attaches the reverse osmosis drain line to your under sink drain pipe. It can be installed by drilling a hole into said drain pipe and bolting the drain saddle to the pipe.
If you have any thoughts about the question, does a reverse osmosis system need a drain, please don’t hesitate to leave a comment below!
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