Water supply and sanitary notes

Source of Water.

a. Surface source:- the source containing the surface water is the surface source. Eg, Rain, River, Stream, Pond, lake, etc.

b. Ground source:- the source containing below the surface of the earth. Eg, Well (shallow & deep), Artision gallery, Spring, etc.

# Rain is the main source of water on the earth.

# The water obtained from hill spring is found in the purest form.

# Oligotrophic lake:- it gives purest waters, water pollution is less. waters are clear, transparent and nutrients poor.

# Mesotrophic lake:- a slight increase in the nutrients. lakes are green-colored and rich in aquatic plants.

# Eutrophic lake:- the lake is turbid, nutrient (Nitrates and phosphate-rich, rich in blue-green algae, coarse fish.

Necessity of water supply.

  • to supply safe drinking water to consumers with sufficient pressure, discharge.
  • to improve health and minimize poverty.
  • to safe environment and sanitation, etc.

# Department of water supply and sewerage (DWSS) was established in 1972.

# As per the annual report DWSS Nepal of FY 2072/73, coverage of water supply and sanitation is 87% and 87.3% respectively.

Quality of water.

Impurities:- there are three types of impurities present in water.

  • Suspended solid:- its Sources – clay, Algae, Fungi, Organic/Inorganic minerals, Oils, Grease, Silts, Plants fibres, Bacteria, etc. Size varies 0.1 to 0.001 mm.
  • Colloidal solid:- its sources – Silica, Iron Oxide (Fe2O3), Alumina (Al2O3), Manganese Oxide (MnO2), Bacteria, Algae, etc. Size varies 10-3 to 10-6 mm.
  • Dissolved solid:- its sources – Inorganic/Organic solid, decay product of vegetation, Ca++, Na+, K+, Mn++, H+, etc. Size varies 10-6 to 10-9.

Water sample:- water samples from streams/rivers should be collected 40-50 cm below the surface. For physical test clean bucket and for a chemical test glass bottle of more than 2 ltr capacity is required.

1. Wholesome Water:- also known as potable water. Water that does not contain harmful impurities and does contain other salts and impurities either good for health or unharmful to health is called wholesome water.
2. Polluted Water:- Water containing undesirable substances due to which water becomes unfit for domestic uses. It may or may not contain pathogenic bacteria.
3. Contaminated Water:- It is water containing pathogenic bacteria.
4. Sterilized Water:- The water which does not contain any types of bacteria either good or harmful for health. It is normally used for medical purposes.

Demand of water.

a. Domestic demand:- for drinking, bathing, cooking, washing, flushing, cleaning, etc. Domestic demand depends upon,

  • customs and habit of people.
  • system and supply.
  • climate condition.
  • method of sewage disposal.
  • quality of water,
  • distribution pressure.
  • method of charging.
  • size of community.
  • alternative sources.
1. Domestic demand as per Indian Standard is 135 ltr/capita/day.
2. Domestic demand as per Nepali standard via stand post 45 lpcd, via private connection 65 lpcd (partially ventilated/semi-urban) and via private connection 112 lpcd (fully ventilated/urban).

b. Industrial and commercial demand:-

c. Public demand and livestock demand:-

d. Fire demand:- fire demand calculation formula based on population.

  • National Board of Fire Underwriter (Q) = 3860 √P [1- 0.01√P].
  • Kuiching (Q) = 3180√P.
  • Freeman (Q) = 1135 (P/5 + 10).
  • Burton (Q) = 5660 √P.

where, P = population in thousand, Q = quantity of water in ltr/minute.

Based on nature of material,

F = 3.7 x C x √A

where, F = ltr/sec, C = coff. of material (1.5 for wood, 1 for ordinary construction and 0.6 for fire resistant construction), A = total area in all storey (sq.m).

e. Leakage, losses, and thefts:- leakage occurs due to bad quality of the pipe, appurtenances, and bad workmanship. losses due to bad management and thefts are illegal tappings.

Non-domestic demand.


  • big animal (cow/buffalo) :- 45 ltr/animal.
  • small animals (pig,goat) :- 20 ltr/animal
  • poultry (Bird) :- 20 ltr/100 birds.

2. Hospital with attached toilet:- 500 ltr/bed.

3. Health post without toilet:- 1000 ltr/bed.

4. Health post with toilet:- 2500 – 3000 ltr/day.

5. School,

  • day school:- 10 ltr/pupil.
  • boarder:- 65 ltr/pupil.

6. Public institution:- 500 – 1000 ltr/day.

7. Restaurant/tea stall:- 500 – 1000 ltr/day.

8. Tourist hotel (unclassified):- 200 ltr/bed.

# minimum water demand is 65% of total demand.

Population Forecasting Method.

  • Arithmetical increase method:- it gives too low result for young cities and best suited for old town with sluggish growth.

Pn = P + n x a

where, Pn = population after ‘n’ decades, P = present population, a = average increase per decades.

  • Incremental increase method:-

Pn = P + n x a + n(n+1) x b/2

where, b = incremental increase per decade.

  • Geometrical increase metjod:- it gives very high rate and best suited for cities in their initial stage of growth. In Nepal Geometrical increase method for population forcasting is done.

Pn = P(1 + r/100 )n

where, r = percent growth per decade. In Nepal 1.35 % as per population census 2011.

  • Decreasing rate of increase method:-
  • Graphical method:-
  • Comparision method:-

Water Related Disease.

a. Water Brone Disease:- are caused due to use of contaminated or polluted water. water borne diseases have five categories.

  • Bacterial Origin:- ex, cholera, typhoid, paratyphoid, bacillary dysentary.
  • Protozoal Origin:- ex, amoebic dysentary.
  • Virus Orizin:- ex, poliomyelities infection, hepatitis, yellow jaundies.
  • Helminthal Origin:- ex, hookworm, round worm, tapeworm.
  • Chemical Origin:- It consists of,
  1. Methemoglobinemia:- cause due toexcess present of nitrites in drinking water. Blue baby syndrome occurs only in infants less than 6 month old baby.
  2. Fluorisis:- dental fluorosis – enamel of teeth is destroyed.
  3. Skeltel fluorosis:- caused bone loose elasticity and become stiff. Blood coagulation and tissue respiration are also affected.
  4. Goitre:- (endemic) caused due to dificiency of iodine in drinking water. Thyroid gland affected.
  5. Lead:- poision present in water.

b. Water Washed Disease:- caused due to the less utilization of water. ex, constipation, skin, trachoma, lice, itch, etc. Inside body water decrease by 1% then feel thirsty, 5% less feel fever, 10% less then feel weakness.

c. Water-Based Disease:- caused due to bacteria present in water that enters into the human body through the skin. ex, sitosovisis, parasites, etc.

d. Water Vector Disease:- caused due to bitting of bacteria (mosquito, protozoa) present in water and spreading lay eggs around the water. ex, malaria, filaria, bath fever, yellow fever, dengue, chicken guinea, etc.

Types of water supply pipe.

  1. GI Pipe (Galvanized Iron):- resist high pressure than HDPE pipe.
  2. HDPE Pipe (High Density Polyethyene):- mostly used in rural gravity water supply system.
  3. PPR or PPRC Pipe (Polypropylene Random Copolymer):-
  4. PVC Pipe (Polyvinyl Chloride):-
  5. UPVC Pipe (Unplastized Polyvinyl Chloride):-
  6. CPVC Pipe (Chlorinated Polyvinyl Chloride):-
  7. CI Pipe (Cast Iron):-

GI and HDPE Pipe Series (Identification).

a. GI Pipe, (Identity – color one place at end):-
#Heavy – Red,
#Medium – Blue
#Light – Yellow.

Old Modal HDPE Pipe (PE 63) & New Modal HDPE Pipe (PE 100):- Identify color throughout

Pipe Kg Color Class Head Re…
2 kg/cm2 Grey20 m PE-63
2.5 kg/cm2 Red 2nd 25 m PE-63
4 kg/cm2 Blue 3rd 40 m PE-63
6 kg/cm2 Green 4th 60 m PE-63
10 kg/cm2 Yellow 5th 100 m PE-63
Pipe KgColorHeadRe..
4 kg/cm2 Blue40 m PE-100
6 kg/cm2 Green60 m PE-100
10 kg/cm2 Yellow100 m PE-100
12.5 kg/cm2 Purple125 m PE-100
16 kg/cm2 White160 m PE-100



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