RO Waste Water Uses for Plants & Benefits

reviewed by Christina Lopez

Reverse osmosis (RO) is a technique deployed for the purification of water by removing unwanted contaminants or impurities present in water, such as minerals, calcium, sodium, chloride, and organic waste. This purification is performed by pushing the water under pressure through a semi-permeable membrane that separates the unwanted solute from the purified drinking water.

The unwanted solute is known as waste or rejected water and is produced in large quantities, as for every 1 liter of purified water, there are 3 liters of wastewater created.

This purified water is free from all impurities and even waterborne diseases. Furthermore, instead of wasting the rejected water, it can be used for various other activities such as flushing toilets, pre-rinsing laundry, swimming pools, and fountains and watering plants, etc.

RO wastewater for watering plants:

 RO wastewater for watering plants:
RO wastewater for watering plants:

First of all, the rejected water can be effectively used to water the house plants and is one of the few irrigation sources. This water may be deemed unsuitable for drinking or bathing. However, it is only slightly less pure than the water initially entering the filter.

Thus instead of sending this wasted water back into the sewage system, it can be used for watering plants as it has no significant adverse effect on plants.

Nonetheless, it is vital to check the quality of the water and its effect on your garden plants. Test the wastewater out on each plant by watering your plants with the RO wastewaterfor a few days to see how it affects the plants. This will help in understanding which plant responds better to hard water.

RO Water Benefits:

Moreover, the benefit of using Reverse Osmosis filters is that it produces a consistent amount of wastewater, which can be used on all the plants in a decent-sized garden. Also, the city water has a lower TDS (Total Dissolved solids) level, which means it is safe enough to be used for watering plants compared to harder water in rural areas where the water has numerous amounts of minerals ions present.

Furthermore, using this wastewater to water garden plants results in the RO system being more efficient in terms of its purpose and cost. The only disadvantage of using the RO system wastewater is that it has a higher sodium concentration. This concentration can affect soil fertility and cause the soil's micro and physicochemical composition to change in the longer run.

Therefore, the safer way of using wastewater to water plants it should be diluted using tap water to avoid soil infertility in the long run. The most beneficial aspect of using the rejected water for irrigation and watering plants is that it saves large quantities of drinking water to be wasted in regions where there is a scarcity of water to begin with, for example, Africa. This way, not only are the plants being sufficiently watered, but purified water is also utilized for drinking purposes only.

Optimum TDH and pH levels of water for plants:

The soil's pH plays a crucial role in plant growth and affects several factors, e.g., nutrient leaching, soil bacteria, nutrient availability, etc. The soil's bacterial activity, which releases nitrogen from the organic matter, is affected by the pH of the soil because bacteria work best in the range of 5.5 to 7.0.

Plant nutrients drain rapidly with pH below 5.0 than from the soils with a pH of 5.5 to 7.5. The nutrients of plants are most available to plants in the range of 5.5 to 6.5. If the pH of the soil is extremely acidic or alkaline, the soil becomes sticky and hard to cultivate.

The optimum TDS level for plants should be up to 2100 PPM. The sodium percentage should be less than 60%, as high sodium content is very harmful to soil fertility. TDS level above the optimum value can result inplant damage. Waste RO water contains a high level of TDS. However, it can be used for watering plants if diluted with tap water.


Simply put, RO wastewater from water purifiers can be used for watering plants depending on the optimum TDS and pH levels of water for plants. RO water is very beneficial for the soil not only because of its purpose but also because it's cost-effective.

Furthermore, with the balanced amount of the TDS level, soil fertility can increase, which results in the healthy growth of plants. Moreover, the optimum pH level (5.0 - 7.0) should be monitored so that the bacterial activity in the soil can work properly and provide nutrients to the plants.


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About Christina Lopez

Christina Lopez grew up in the scenic city of Mountain View, California. For eighteen ascetic years, she refrained from eating meat until she discovered the exquisite delicacy of chicken thighs. Christina is a city finalist competitive pingpong player, an ocean diver, and an ex-pat in England and Japan. Currently, she is a computer science doctoral student. Christina writes late at night; most of her daytime is spent enchanting her magical herb garden.

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