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The storage cistern within a consumer’s premise serves several functions including (a) providing sufficient storage of water to safeguard against disruption of water supplies over a twenty-four hour period, (b) maintaining suitable pressures within the distribution piping system serving a building and (c) safeguarding against backflow of stored and used water to the external reticulation system. A schematic drawing illustrating the basic components of a storage cistern is depicted in Figure C.3.

a. Capacity

i. Generally, the effective capacity of a storage cistern (i.e. the maximum volume of water that can be drawn for use over a twenty-four hour period) shall provide for one day’s water consumption needs of different types of premises. The minimum storage capacities for different types of buildings are specified in Table C.4, Table C.5 and Table C.6.

Table C.4 : Minimum storage capacities for hospital, airport and particular industry

Type of Building

Minimum storage capacity for one day

(liters)

Hospital 1500 / bed

Airport 25 / passenger

Heavy Industry 65000 / hectare

Medium Industry 50000 / hectare

Light Industry 33,000 / hectare

Light Industrial Workshop 1500 / unit

Wet Market 1500 / stall

Dry Market 450 / stall

Semi Detached / Bungalow / Workshops 1500 / unit

Table C.5: Minimum storage capacities for residential / shop premises

Type of Building Minimum storage capacity for one day (liters)

Dwelling Houses (Rural) 800 / unit

Dwelling Houses And Flats With

Individual Storage Cistern(Urban) 1300 / unit Flats With Shared Storage Cistern 1000 / unit Low Cost Houses (Rural And Urban) 800 / unit Shop House (Single Storey) / Low

Cost Shop 2000 / unit

Shop House (Double Storey) 3000 / unit Shop House (Three Storey) 4100 / unit Shop House (Four Storey) 4550 / unit

Table C.6: Minimum storage capacities for other types of buildings

Type of Building Minimum storage capacity for one day (liters)

Hotels 270 / person

Hostels 180 / person

Day Schools / Kindergarden 30 / person

Boarding Schools 180 / person

Restaurants 14 / person

Mosque Or Other Place Of Worship 50 / person Barrack (Army And Police) 250 / person Office / Complex / Commercial

(Domestic Usage) 1000 / 100 square metre Community Centres Or Halls 1000 / 100 square metre Education Institutions (Other Than

School And Kindergarten) 100 / student Institution Of Higher Learning With

Hostels Facilities 250 / student

Prison 250 / person

Army Camp 250 / person

Bus Terminal 900 / service bay

Petrol Kiosk (With Car Washing Bay) 50,000 / unit Petrol Kiosk (Without Car Washing

Bay) 10,000 / unit

Stadium 55 / person

Golf Course 1000 / 100 square metre

Warehouse 1500 / unit

Others As per the estimated water

demand by the owner

ii. For premises where the population is transient and unknown the required storage cistern capacity may be estimated by the number of, and the types of, fittings installed as denoted in Table C.7.

Table C.7 : Estimation of Water Demand based on Types of Fittings Storage Capacity Type of Fittings

1. 450-900 liters Per Shower

2. 910 liters Per Slipper Bath

3. 180 liters Per Water Closet

4. 90 liters Per Lavatory Basin

5. 90 liters Per Sink

6. 180 liters Per Urinal

7. 180 liters Per Bed Pan Washer

8. 225 liters Per Wash-Up Sink

iii. Storage cisterns for hospitals, airports and medium and heavy industries shall have a storage capacity of not less than two days water demand based on projected consumption pattern in accordance with Table B.1.

iv. Factories with future expansion plans shall allocate sufficient space for ultimate storage requirements.

v. Top Water Level (TWL) for suction cisterns and roof storage cisterns shall be referred to Ordnance Datum Level.

vi. Separate water storage cisterns and distribution pipes shall be provided for supplying water to food courts in buildings, and for kitchen and food and beverage outlets at hotels, hospitals and convention centre’s.

b. Pipeworks and Materials

i. Water storage cistern with a capacity of 4,500 liters and below shall have an overflow pipe which shall function as a warning pipe and shall be installed at a visible location.

ii. The overflowing level of the warning pipe shall be set 50mm above the water line and not less than 50mm below the top edge of the cistern.

iii. Water storage cisterns with capacity of above 4,500 liters shall have separate overflow and warning pipes which shall be installed at a visible location so that visual detection of overflows can be made.

iv. Overflow pipes and scour pipes shall be one size larger than an incoming pipe and not smaller than the outlet distribution pipe.

v. Scour pipes shall be installed at the lowest point (underneath or side) of the cistern and channeled to the nearest floor trap, sump or drain at a visible location.

vi. Materials permitted to be used in the construction of water storage cisterns shall conform to the Commission’s registered list or other permitted Recognised Standards.

c. Dedicated Water Storage Cisterns

i. These provisions shall be applicable for every dedicated storage cistern installed to serve a single consumer occupying any type of landed property, shop house, shop offices and flatted factory which is served by an individual meter.

ii. A hatch of not less than 600mm x 600mm shall be provided to access to the water storage cistern if the latter is placed within a roof truss area of a building.

iii. If the water storage cistern is placed other than within the roof truss area, it shall be shaded against the sun and be readily accessible for maintenance and replacement; provided that it may also be located in an unshaded area so long as the storage cistern is constructed from materials that are ultra violet resistant.

iv. The storage cistern shall be placed on flat platform which prevents

v. A professional structural engineer as stipulated in the second schedule of competent persons who shall certify that cistern and its support system is structurally sound and is safe.

vi. The storage cistern shall be placed in a position where the interior of the cistern may be readily inspected and cleaned. A clear space of not less than 375mm shall be provided between the top of the cistern and any obstruction.

vii. A stable platform of not less than 600mm wide shall be provided at least along three sides of a cistern for assisting in maintenance of the tank.

viii. The storage cistern shall be provided with a chlorine resistant cover which is dust and mosquito-proof. Such cover shall be provided with an opening of a size not less than 300mm diameter located directly above the float operated valve or inlet valve of the storage cistern to enable easy maintenance without having to remove the entire storage cistern cover.

d. Shared water storage cisterns

i. These provisions shall apply to a single storage cistern that serves more than one customer (e.g. parcel owners in a condominium, multi-story flats, high rise buildings, etc.).

ii. Secured access shall be provided for shared storage tanks. Persons entering secured storage tank areas shall be registered and their intent recorded in a Registration Booklet maintained by the Management Corporation or Owners of buildings.

iii. A storage cistern (including any tap fitted to the storage cistern) and its ancillary equipment shall be kept properly locked at all time.

iv. All roof storage cisterns shall be easily accessible with proper staircases located within the premise. Only spiral or walk up RC staircases shall be used and no cat ladder shall be allowed.

v. There shall be proper access and ancillary facilities provided for regular inspection and cleaning of the water storage cistern. A minimum head room of 900mm, and similar horizontal clearances, shall be provided on top of and around the storage cistern.

vi. The storage cistern shall be placed on a flat RC slab or RC plinth (as the case may be) completes with proper drainage system discharging to a conspicuous location, such as a scupper drain or floor traps.

vii. The base of the storage cistern shall be fully supported over its whole area by a durable, rigid, flat and level platform sufficiently strong to withstand the weight of the cistern without deflection when filled with water. For FRP / GRP panel storage cisterns and hot dipped galvanized storage cisterns, support or skids shall be provided between the cistern and the concrete plinth.

viii. Storage cisterns of 10,000 litres or more shall have internal compartments to facilitate maintenance of the cistern. Alternatively, multiple cisterns may be employed. An equalizing pipe shall be provided between each compartment or between each separate storage cistern supplying water to the same distribution pipe.

ix. Ladders to access the interior of the storage cistern shall be of stainless steel grade 316

x. All internal reinforcement (tie rods) if required for the storage cistern shall be of stainless steel grade 316.

xi. All internal bolts, nuts and washers shall be of stainless steel grade 316.

xii. Bolts, nuts and washers external to the storage cisterns and roof plate shall be hot dipped galvanized to MS 740 : 1981.

xiii. External ladders to access to the top of the storage cistern may be of stainless steel, aluminium or hot-dipped galvanized steel.

xiv. All storage cisterns constructed of concrete or steel panels for domestic water systems shall be lined with HDPE or other corrosion resistant material for ease of cleaning.