Is Your RO Water Safe to Drink?: A Fact File

BOOM investigates claims of RO water causing vitamin D deficiency and tap water being a better alternative.

Would you ditch your water purifier for tap water, if you knew the filtration process was reducing minerals in the water you drink?

That's the advice from a former scientist at the National Environmental Engineering Research Institute (Neeri)

Earlier in July, the former director of Neeri - Tapan Chakroborty, said that people should drink tap water and not water from RO purifiers. (Read more about it here)

What is RO water?

Reverse osmosis or RO makes drinking water safe for consumption. Surface water contains dissolved salts which the reverse osmosis process removes through a semi-permeable membrane.

RO is one kind of purifier from the three main types of purifiers along with UV (ultraviolet) and UF (ultra filtration). Only RO water purifier removes metal particles like arsenic, fluoride, lead, chlorine, nitrates and sulfates.

Tapan Chakroborty also claimed that RO water removes calcium and magnesium which are essential minerals present in the water.

BOOM contacted Chakroborty who said that he drinks water directly from the tap at his residence in Nagpur.

When asked whether his advice could be implemented at the national level, he replied in the affirmative.

"Yes. My statement can be applied for everybody across the country. Except the monsoon, where we boil the water or use alum, I drink water directly from the tap," Tapan Chakroborty, former director, Neeri.

Viral video questions purity of RO water

Post Chakraborty's statement, a video claiming RO water is responsible for vitamin D deficiency, created originally in May 2019, resurfaced online.

The video was made by the Kalgidhar Trust- Baru Sahib, a Punjab based trust that primarily builds educational organisations for under privileged children of rural Punjab.


BOOM found that the scientific studies referred to in the video are around 20-25 years old. There is no recent research backing the effect of RO water on vitamin D.

We also reached out to the trust through its Facebook page. They told us that the trust has stopped using RO water at their main headquarters and are finding alternatives for RO as well as adjusting the Total Dissolved Solids (TDS levels) at 300mg/l at their other schools.

BOOM has not independently verified these claims.

Can drinking RO water lead to vitamin D deficiency?

Vitamin D is an essential vitamin which helps the body absorb calcium. Sunlight is a major source of vitamin D.

When BOOM asked Tapan Chakroborty about RO water causing vitamin D deficiency, he disagreed

"Vitamin D absorbs calcium in the body, but it is not synthesized from water," Tapan Chakroborty, former director at Neeri told BOOM.

"I do not support this claim."

The same claim was also debunked by Dr. Ambarish Mithal, an endocrinologist from Delhi, stating that calcium deficiencies could be linked to RO water, but not a vitamin D deficiency.



Whether or not to use an RO purifier boils down to the levels of total dissolved solids (TDS) in drinking water.

What are Total Dissolved Solids?

Total dissolved solids (TDS) contain inorganic salts such as calcium, magnesium, potassium, sodium, chlorides, and other organic matter along with various bacteria that are found in the water. They originate from various natural and artificial sources including industrial waste.

The World Health Organisation recommends that if water has TDS less than 300mg/l, it is excellent for consumption.

TDS levels and their acceptability
WHO- TDS levels and their acceptability in drinking water

Water purifier brands on TDS levels

Most of the RO purifier brands have categorically stated that consumers should be well aware of the TDS levels while giving the tables depicting the permissible levels. They have also stated that the consumers should not install RO purifiers if their water has low TDS levels.

You can access the Kent and Eureka Forbes TDS explanations here and here.

"In most urban areas, water comes from various sources, through pipelines, and tankers, where the quality is compromised, " Dr. Abhay Kumar, Chief Science Officer at Eureka Forbes, said.

"However, in the rural context, certain areas like Rajasthan and Warangal have arsenic and fluoride in water. It is wiser to get an RO at such times. Minerals such as calcium and magnesium, people can even get them through food."

Is tap water a safer alternative to RO water?

Around 600 million Indians face high to extreme water stress and about 2,00,000 people die every year due to inadequate access to safe drinking water, according to the NITI Aayog's 2018 Composite Water Resource Management report.

"Tap water without boiling or filtration is definitely not safe to be consumed," Nitesh Rikame, Senior Officer, CSR at Watershed Organisation Trust, a Pune-based organisation working towards providing access to safe drinking water to vulnerable communities, told BOOM.

"However, after the first round of filtration, if the TDS levels are lesser than 500mg/l as per the Bureau of Indian Standards, then that water is safe to be consumed," Rikame said.

Experts agree it is important for individuals know about TDS levels in their water. However, most consumers are not aware about the existence of solids in drinking water.

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