TDS, pH and hardness — what the label numbers mean

Turn a Clear Sea bottle around and you will find a list: pH value, turbidity, total hardness, chloride, calcium, magnesium, fluoride, sulphate, nitrate, iron, total dissolved solids. It looks like a chemistry exam. It is really just a description of what is in the water besides water.

You do not need to understand all of it. But three figures do most of the work, and once you can read those three, the rest falls into place.

1. TDS — total dissolved solids

TDS is the combined weight of everything dissolved in the water: minerals, salts, and traces of metals. It is measured in milligrams per litre (mg/l).

The important thing about TDS is what it is not. It is not a purity score, and a lower number is not automatically better. TDS does not distinguish between harmless calcium and something you would rather not drink — it just weighs the total. Water with almost zero TDS is chemically clean but tastes flat and dull, which is exactly why demineralised water is unpleasant to drink.

Very low (under ~40 mg/l) — tastes flat. Typical of unremineralised RO output.
Moderate (~50–250 mg/l) — the range most people find crisp and pleasant.
High (above ~500 mg/l) — starts tasting salty, bitter or metallic depending on what is dissolved.

Why a TDS meter tells you less than you think

Those little pen-shaped meters measure electrical conductivity and convert it to an estimated TDS. That tells you how much is dissolved — never what. A meter cannot detect bacteria at all, and bacteria are the thing most likely to actually make you ill.

2. pH — acidic or alkaline

pH runs from 0 to 14. Seven is neutral, lower is acidic, higher is alkaline. Drinking water is normally kept in a band around neutral — the limit printed on our label is 6.5 to 8.5, and Clear Sea sits close to the middle of it.

Within that band, pH mostly affects taste and how the water behaves in pipes, not your body. Your stomach maintains a strongly acidic environment regardless of what you drink, so a glass of slightly alkaline water does not meaningfully change your body's pH. Claims that it will should be treated with suspicion.

3. Total hardness

Hardness measures dissolved calcium and magnesium, expressed as an equivalent amount of calcium carbonate (CaCO₃). It is the reason a kettle furs up and soap lathers poorly in some places and not others.

Hardness at ordinary drinking levels is not a health problem — calcium and magnesium are minerals you need. Very hard water is mainly an inconvenience: scale in kettles and geysers, spots on glassware, more soap needed. Very soft water tastes thin.

The rest of the list, briefly

Parameter	What it tells you
Turbidity (NTU)	How cloudy the water is. Low turbidity means suspended particles have been filtered out — it also makes disinfection more effective.
Colour (Hazen)	Visible tint. Should be effectively nil in packaged water.
Chloride	Common salt content. High levels give a salty taste.
Sulphate	Bitter taste at high levels; can have a laxative effect well above the limit.
Fluoride	Small amounts help teeth. Too much over years causes fluorosis — a genuine problem in parts of India, which is why the limit is tight.
Nitrate	Usually a marker of agricultural or sewage contamination in groundwater. Particularly important for infants.
Total iron	Causes a metallic taste and rust-coloured staining. Aesthetic more than dangerous at low levels.
Calcium & magnesium	The minerals behind hardness — and the ones worth putting back after reverse osmosis.

Why RO water gets minerals added back

Reverse osmosis pushes water through a membrane fine enough to hold back dissolved solids. It is very effective — and indiscriminate. It removes the heavy metals and salts you want gone, and the calcium and magnesium you would rather keep, in the same pass.

That is why a controlled remineralisation stage follows RO in our process. It brings the mineral profile back into a sensible range so the water tastes like water instead of tasting like nothing.

This is the practical difference between "purified" and "purified, then balanced". Stripping everything out is the easy half. Putting the right things back in measured amounts is the half that decides how it tastes.

The short version

TDS measures how much is dissolved, never what — lower is not automatically better.
pH between 6.5 and 8.5 affects taste, not your body's chemistry.
Hardness is calcium and magnesium; at normal levels it is a kettle problem, not a health one.
Fluoride and nitrate have tight limits for real reasons.
No meter detects bacteria — that is what testing and sealed packaging are for.

How to check ours

Every Clear Sea pack carries a batch number. Send us that number and we will share the corresponding test report for it — not a generic brochure figure, the actual batch you are holding. Our FSSAI licence number, 12725038000710, is printed on the same label.

You can also see our typical values for all fourteen parameters on the water quality section of the homepage.

Check the limits against the current standard

Packaged drinking water in India is governed by BIS standards, which are revised from time to time. The permissible limits shown on our label and website reflect the standard we are certified against — if you are comparing brands, check that you are comparing against the same revision.