TDS gets all the attention, but pH matters too. It tells you whether water is acidic or alkaline – and it explains why some RO water tastes slightly sour or flat. Here is what pH your drinking water should have and how to check it.
What is pH?
pH is a scale from 0 to 14. 7 is neutral; below 7 is acidic, above 7 is alkaline. Each step is a tenfold change, so pH 6 is ten times more acidic than pH 7.
Safe pH for drinking water in India
The Indian standard BIS IS 10500:2012 sets the acceptable pH range for drinking water at 6.5 to 8.5. Water in this range is considered fine for daily drinking.
| pH | What it means |
|---|---|
| Below 6.5 | Acidic – can taste sour and corrode metal pipes |
| 6.5 – 8.5 | Within BIS range – fine to drink |
| Above 8.5 | Strongly alkaline – can taste bitter or soapy, may leave scale |
Why is RO water sometimes acidic?
RO removes minerals like calcium and bicarbonate that buffer pH, but dissolved carbon dioxide passes through the membrane. The result is RO water that often reads around 6 to 7. It is not harmful in itself, but some people find the taste flat. An alkaline / mineral filter after RO adds minerals back and usually lifts pH into the comfortable range.
How to test pH at home
- Take a clean test tube or small glass of water (fill to the mark if your kit has one).
- Add the number of pH drops given in the kit instructions.
- Shake gently and compare the colour with the chart within the time mentioned.
- Test both tap water and RO water for comparison.
Our Water Testing Kit (₹399) has pH and ORP drops plus a TDS meter. Read how to use a TDS meter too.
Does alkaline water cure diseases?
No reliable evidence supports claims that alkaline water cures disease. An alkaline stage mainly improves taste and keeps pH in the normal range. Read our honest take: alkaline filter in RO – worth it?.
Frequently asked questions
What is the best pH for drinking water?
Anything between 6.5 and 8.5 meets BIS. Around 7–8 is what most people find tastes best.
Is pH 6 RO water safe?
It is slightly below the BIS range. It is not immediately harmful, but an alkaline/mineral stage is recommended to bring it up.
Is TDS the same as pH?
No. TDS measures how much is dissolved; pH measures acidity. See TDS for drinking water.
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