IS 1070 : 1992Reagent Grade Water

IS 1070:1992 is the specification for reagent grade water — the purity grades of water used in laboratories for chemical and materials testing, including the construction-materials lab work that underpins quality control (cement, concrete, soil, water-quality and chemical tests). It defines the grades of purified water and their limiting parameters.

It matters on projects because the validity of acceptance tests depends on the water used in them. It is read with the testing stack:

• IS 3025 (parts) — methods of sampling and test for water (uses reagent water as the blank/dilution)
• IS 4031 (parts) — physical tests for cement · IS 4032 — chemical analysis of cement
• IS 2720 (parts) — laboratory tests on soils
• IS 456 — *mixing/curing* water quality (a different, field requirement — not reagent water)

IS 1070 classifies purified laboratory water into grades of increasing purity, each with limits on:

• Conductivity / specific resistance (the headline purity indicator — dissolved ions)
• pH and oxidisable matter (organics)
• Residue on evaporation (total non-volatile matter)
• Heavy metals, silica, chloride and other trace contaminants for the higher grades

Lower grades suit routine rinsing and general preparation; the higher grades are required for trace chemical analysis and sensitive instrumental tests. Reagent water is produced by distillation, deionisation/ion-exchange or reverse osmosis (often in combination), and — critically — its purity degrades on storage (CO₂ absorption raises conductivity, container leaching adds ions), so freshly-produced water of the correct grade must be used for the test that demands it.

Scenario: running IS 4032-type chemical analysis and IS 3025 water-quality tests in the site/QC lab.

Step 1 — identify the demand: trace chemical analysis (e.g. chloride/sulphate in water or cement) requires a high IS 1070 grade — ordinary tap or even single-distilled water carries enough ions to corrupt a low-level result.

Step 2 — produce/verify: generate water by RO + deionisation (or double distillation); verify conductivity against the IS 1070 limit for the required grade before use.

Step 3 — use fresh: prepare blanks, standards and dilutions with the freshly-checked water; do not use water that has stood in an open/contaminating container.

Step 4 — blank correction: run a reagent-water blank through the method; if the blank is high, the water grade is inadequate and the batch of results is invalid.

Outcome: the acceptance result is only trustworthy if the water behind it meets the IS 1070 grade the method assumes — the blank proves it.

1. Confusing reagent water with concrete mixing/curing water. IS 456 sets *field* limits for water that goes into concrete; IS 1070 is *laboratory* water used to run tests — different purpose, different limits.

2. Using tap/borewell water in chemical tests. Dissolved ions swamp low-level analyses (chloride, sulphate, heavy metals), producing false fails/passes.

3. Ignoring storage degradation. 'Distilled water' that has stood for weeks absorbs CO₂ and leaches from its container — conductivity drifts out of grade; use fresh and re-check.

4. No reagent-water blank. Without a blank, an out-of-grade water silently biases every result in the batch.

5. Wrong grade for the method. A routine grade where the method needs the high grade (or vice-versa, wastefully) — match the grade to the test's sensitivity.

• IS 3025 (parts) — sampling and test for water and wastewater
• IS 4031 (parts) — physical tests for hydraulic cement
• IS 4032 — methods of chemical analysis of hydraulic cement
• IS 2720 (parts) — methods of test for soils (lab water)
• IS 456 — concrete mixing/curing water requirements (field, *not* reagent)
• IS 10500 — drinking water (a different quality benchmark)

IS 1070 is reaffirmed and is methodologically aligned with the international laboratory-water grade systems (ISO 3696 / ASTM D1193) that instrument and reagent suppliers quote — comparable and acceptable when cross-referenced. It is invisible on a construction site but it is the silent foundation of QC credibility: every chloride, sulphate, cement-chemistry and water-quality acceptance result is only as reliable as the water used to run it.

The practitioner discipline for a site/QC lab is simple and rarely enforced: produce water of the grade the test method demands, verify its conductivity before use, use it fresh, and run a reagent-water blank with every batch. NABL-accredited labs do this as routine; site labs frequently do not, which is why disputed durability results so often trace back not to the concrete but to the water in the beaker.