SOP for Purified Water & Potable Water Testing

Formula: H2O
Molecular Weight: 18
Source of Information: WHO/BP/USP
Purpose: To avoid microbial contamination in products.  Liquid as well as solids.
Water Sampling Point Place Tests and Frequency Purpose
SP-1 Between Turbine and Tank Chemical and Microbiological:
Once in a Month
To prove the chemical quality and microbiology of  the well water
SP-2 Between Tank and Sand Filter Chemical and microbiological. Fortnightly To prove the chemical quality of the well water and the change of the microbial Quality in the Tank
SP-3 After Hardness Stabilizing System (Anti-scaling System) Chemical:
Twice a week
To prove the effect of the Hardness stabilizing system
SP-4 Primary storage tank Chemical:
Twice a week
To prove the efficacy of 1st two membranes.
SP-5 After 2nd R/O and UV lights Chemical daily To check the R/O system performance
SP-6 After Passing through UV lights Microbiological once in a week To check the performance of UV lights.
SP-7 Water Storage Tank Chemical Daily or before going to use and Microbiological Twice a week To check the storage water


Water is omnipresent. About three-quarters of the earth surface is covered with liquid water. Water is an important constituent of the earth atmosphere. In combined form, water occurs abundantly in may mineral e.g. Gypsum water occurs in all animal and vegetable tissues. Water is chemically stable compound. SOP for Purified Water & Potable Water Testing acts as a solvent for an unusual range of substances.

Water is divided into four kinds:
1. Nature water
2. Potable water
3. Purified water
4. Heave water


Naturally occurring water contains dissolved minerals indigenous to the region. Natural water contains varying amounts of suspended matter e.g. clay sand, microorganisms, fragments of pants and animals.


This water is fit for drinking providing potable water is one of the most important functions of modern communities. The overall process involves removal of insoluble matter through appropriate coagulating, setting and filtering process the destruction of pathogenic microorganisms by aeration, chlorinating or other methods.


Purified water is prepared by distillation exchange (deionized, demineralized) reverse osmosis are particularly effective in removing electrolytes.


The isotopes of hydrogen, unlike those of other elements have been named, deuterium and tritium. SOP for Purified Water & Potable Water Testing these compounds occur in ordinary water in few ppm.

De-ionized water is most important material used in the manufacturing of all the manufacturing processes.

De-ionized water is supplied from plant situated in the workshop to all the section where required. The water goes through pipeline, which is made of stainless steel. Water filters are provided on supply points and at the D.I. water Plant as well.

Sampling procedure for chemical test

  1. Sample required 800ml from each point. Containers: either of the following clean containers. A conical flask 1000ml with quick fit stopper. A conical flask 1000ml that may be covered with aluminum foil, butter paper etc.
  2. Clean the container with 0.1% w/v detergent solution rinse 3 times with tape water and finely rinse twice with purified water.
  3. Label the container with 0.1% w/v detergent solution rinse 3 times with tape water and finely rinse twice with purified water.
  4. Label the container declaring the sampling point before the sample is taken. Rinse the container twice with the same of which sample is to be taken.

Testing procedure of Purified Water


Clear, Colorless & odorless

Conductivity: (BP)

Determine the conductivity off-line or in-line under the following conditions.


Conductivity cell: 
—electrodes of a suitable material such as stainless steel;
—cell constant: within 2 per cent of the given value determined using a certified reference solution with a conductivity less than 1500 µS·cm-1.

Conductometer Resolution 0.1 µS·cm-1 on the lowest range.

System calibration (conductivity cell and Conductometer):
—against one or more suitable certified standard solutions;
—accuracy: within 3 per cent of the measured conductivity plus 0.1 µS·cm-1.
Conductometer calibration By means of precision resistors or equivalent devices, after disconnecting the conductivity cell, for all ranges used for conductivity measurement and cell calibration (with an accuracy within 0.1 per cent of the stated value, traceable to the official standard).
If in-line conductivity cells cannot be dismantled, system calibration may be performed against a calibrated conductivity cell placed close to the cell to be calibrated in the water flow.


Measure the conductivity without temperature compensation, recording simultaneously the temperature. Temperature-compensated measurement may be performed after suitable validation.
The water to be examined meets the requirements if the measured conductivity at the recorded temperature is not greater than the value.

For temperatures not listed in Table, calculate the maximal permitted conductivity by interpolation between the next lower and next higher data points in the table.
Purified water in bulk is stored and distributed in conditions designed to prevent growth of micro-organisms and to avoid any other contamination.

Acidity or alkalinity

To 10 ml, freshly boiled and cooled in a borosilicate glass flask, add 0.05 ml of methyl red solution R. The solution is not coloured red.
To 10 ml add 0.1 ml of bromothymol blue solution R1. The solution is not coloured blue.

pH (USP/NF):

Between 5.0 & 7.0, determined potentiometrically in a solution prepared by the addition of 0.5ml of saturated potassium chloride solution to 100ml of test specimen.

Oxidisable substances

To 100 ml add 10 ml of dilute sulphuric acid R and 0.1 ml of 0.02 M potassium permanganate and boil for 5 min. The solution remains faintly pink.


To 10 ml add 1 ml of dilute nitric acid R and 0.2 ml of silver nitrate solution R2. The solution shows no change in appearance for at least 15 min.


To 10 ml add 0.1 ml of dilute hydrochloric acid R and 0.1 ml of barium chloride solution R1. The solution shows no change in appearance for at least 1 h.


Maximum 0.2 ppm. To 20 ml add 1 ml of alkaline potassium tetraiodomercurate solution R. After 5 min, examine the solution down the vertical axis of the tube. The solution is not more intensely coloured than a standard prepared at the same time by adding 1 ml of alkaline potassium tetraiodomercurate solution R to a mixture of 4 ml of ammonium standard solution (1 ppm NH4) R and 16 ml of ammonium-free water R.

Calcium and magnesium

To 100 ml add 2 ml of ammonium chloride buffer solution pH 10.0 R, 50 mg of mordant black 11 triturate R and 0.5 ml of 0.01 M sodium edetate. A pure blue colour is produced.

Residue on evaporation

Maximum 0.001 per cent.
Evaporate 100 ml on a water-bath and dry in an oven at 100-105 °C. The residue weighs a maximum of 1 mg.

Procedure For Chemical Analysis Of Potable Or Raw Water.


No odour even on working, the taste of impure water is not normally recorded except in case of chlorinated water.


If a pronounced turbidity be present this may be measured and recorded.


Evaporate 100ml in a tared beaker on a steam both to dryness and dry the residue at 105ºC for 1 hour and calculate PPM of residue or solid particles.  (Limit is 500 PPM).


Silver Nitrate Solution:
Dissolve 4.791g of silver nitrate dried at 105ºC in distilled water and dilute to 1 lit. each ml is equivalent to 1mg chlorine.


Dissolve 0.164 g of sodium chloride dried at 105ºC in distilled water and dilute to 1 lit. Each ml is equivalent to 1mg of chlorine as chloride.


Dissolve 5g of Pot. chromate in distilled water dilute to 100ml.


To 100ml of the sample, add 1ml of Potassium chromate solution and titrate with silver nitrate solution.  With constant stirring until there is the slightest perceptible reddish color.  Substract 0.2ml from the reading to allow for the excess required to form the colored silver chromate.  If the volume required is more than 25ml, repeat the determination with a smaller volume of sample after diluting it to 100ml with distal water.
If the pH of the sample is less than 6.8 neutralizer adding a solid calcium carbonate.  If the pH is above to determine the volume of N/10 nitric acid, required to neutralize 100ml of the sample and add this volume to another 100ml portion together with a trace of calcium carbonate, before titrating with the silver nitrate solution.
Each ml of 0.1NAgNo3=3.55mg of Cl   or 35.5 PPm of Cl.


Measure 100ml of the sample into 250ml conical flask, add 100ml of ammonia buffer and mix, add 4 to 6 drops of Eriochrome Black T and mix.  In the presence of calcium or magnesium ions the mixture will be red with exceptionally hard water it is advisable to add the indicator solution.
Titrate with N/100 E.D.T.A with continuous skaking.  At the end point the color changes from red to blue.
Ppm/ml =Volume consumed x 10


To 100ml add 2ml of alkaline mercuric potassium iodide TS, any yellow color produced immediately is not darken than that of a control containing 50ug of added NH3 in high purity water.

Poisonous Metals:

Concentrate the sample to one fifth of into volume after acidifying with a few drops of HCl.  Add ammonia and Hydrogen Sulfite solution, darken in color indicates the presence of lead, copper or iron but zinc does not show divide the solution into two portions, acidify one portion with hydrochloric acid; disappearance of the color indicates the absence of lead and copper to the other portion add potassium cyaxide solution persistence of the color indicates the presence of lead confirmatory test.


Acidify 50ml of the sample with sulfuric acid add 1% Potassium permegenate solution until slightly pink color persists.  Filter and add 5% solution of Potassium ferrocyanide of iron is present a blue color is produced.

P- Value (Phenolphthalein value):

To 25ml sample add 2 drops of phenolphthalein solution and titrated with 0.02N sulfuric acid.
Phenolphthalein value =
T x 4 x 10 =PPM
T = value of 0.02N H2SO4
5.10 M – Value:
To 25ml sample add 2 – 3 drops of methyl orange and titrate with 0.02N sulfuric acid.
Methyl Orange Value:
T x 4 x 10 =PPM
T = value of 0.02NH2SO4


When a solution of a nitrate is mixed with a equal volume of sulfuric acid, the mixture is cooled and a solution of ferrous sulfate is super imposed a brown color is produced at the function of the two liquids.  When a nitrate is heated with sulfuric acid and metallic cooper, brownish red fumes evolved.  Nitrates do not decolorize acidified potassium permanganate.


Take about 50ml of water add 1ml of hydrochloric acid and 1ml of Barium chloride solution.  A white precipitate is produced.  Any opalescence produced is not more intense than that of sulfate standard solution (400 ppm SO4) prepared according to BP sulfate standard solution.


Nitrites are rarely present in natural waters except in minute traces and a qualitative test is all that is required.

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