ISO/TR 7035-2:2024

Technical
Report
ISO/TR 7035-2
First edition
Design and asset management of
2024-09
DIP for water application —
Part 2:
Design, installation and operation
Conception et gestion des actifs des tuyaux en fonte ductile pour
l'alimentation en eau potable —
Partie 2: Conception, installation et exploitation
Reference number
© ISO 2024
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Published in Switzerland
ii
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General . 2
5 Practices to set targets for water supplying system . 2
5.1 Water quality .2
5.1.1 Materials .2
5.1.2 Prevention of back flow .2
5.1.3 Stagnation .2
5.1.4 Cross-connection with other systems .3
5.2 Design life . .3
5.3 Demand for water .3
5.3.1 General .3
5.3.2 Water demand estimate .3
5.3.3 Water for fire-fighting .4
5.4 System security .4
6 Design . 4
6.1 Hydraulic design .4
6.1.1 Sizing .4
6.1.2 Mains .5
6.1.3 Local main .6
6.1.4 Service pipes .6
6.2 Structural design .6
6.3 System layout design .6
6.3.1 Mains .6
6.3.2 Service pipes .7
6.3.3 Valves .7
6.3.4 Reservoirs .7
6.3.5 Pump stations .7
6.4 Protection against aggressive environment .8
6.4.1 General .8
6.4.2 External protection.8
6.4.3 Internal protection .8
7 Hydraulic thrust restraint design . 9
7.1 Hydraulic thrust force and restraint principles .9
7.2 Thrust blocks solutions .9
7.3 Restrained joints solution .9
7.3.1 General .9
7.3.2 Restrained joint systems.10
8 Design of trenchless method . 10
8.1 Pipe jacking . .11
8.1.1 Survey .11
8.1.2 Pipe protection .11
8.1.3 Jacking procedure . . .11
8.2 Horizontal directional drilling . 12
8.2.1 General . 12
8.2.2 Site investigation . 12
8.2.3 Pilot bore design . 12
8.2.4 Upsize the bore . 13
8.2.5 Pulling in. 13

iii
8.2.6 Drilling fluid usage .14
8.3 Design of casing method .14
8.3.1 General .14
8.3.2 Casing design .14
8.3.3 Carrier design . 15
8.3.4 Installation . 15
8.4 Pipe bursting . 15
8.4.1 General . 15
8.4.2 Parameters . 15
8.4.3 Replacement pipe .17
9 Design of pipelines on supports . 17
9.1 Pipelines on land .17
9.1.1 Support design .17
9.1.2 Loading and forces . . .18
9.2 Other cases of supporting pipe .18
10 Installation and hydrostatic test .18
10.1 Installation .18
10.2 Hydrostatic test .18
10.2.1 General .18
10.2.2 Basic design contents for hydraulic test .19
11 Flushing and disinfection .20
12 Operation .20
12.1 Inspection and monitoring . 20
12.2 Maintenance and repair . 20
12.2.1 Maintenance . 20
12.2.2 Pierced pipe maintenance and repair . 20
12.2.3 Broken pipe maintenance and repair . 20
12.3 maintenance and repair for a leaking junction .21
Bibliography .23

iv
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 5, Ferrous metal pipes and metallic fittings,
Subcommittee SC 2, Cast iron pipes, fittings and their joints.
A list of all parts in the ISO/TR 7035 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

v
Introduction
According to the World Health Organization, since 2010, the majority of the world's population lives in cities.
By 2030, six out of every 10 people will live in cities and, by 2050, this proportion will have increased to
seven out of 10 people. The water and wastewater infrastructure of distribution and collection pipes may
have between 5 000 km and 10 000 km of underground piping for water distribution, and a similar network
for wastewater collection, for a city of 100 000 to 500 000 people.
In introducing the practices or known acknowledges of this document due regard has been taken of the
possibility to use ductile iron pipe easily and quickly, as well as the importance of a reliable and safe supply
of water for human consumption and the purpose of trade, industry, agriculture and fire-fighting.
Renovation and repair of pipelines is usually complicated, administratively and technically. In many cases
damage and service interruptions are created to other infrastructure networks (not knowing where these
services run). Along with deterioration of roads and sidewalks the perceived image of the city worsens,
increasing the great list of indirect costs, which is why the long lasting and reliable pipelines like ductile
iron pipes (offering the best cost-effectiveness results), when taken all performances are into account by the
asset management tools, explained in ISO/TR 7035-1.

vi
Technical Report ISO/TR 7035-2:2024(en)
Design and asset management of DIP for water application —
Part 2:
Design, installation and operation
1 Scope
The objective of this document is to assist conceptors, engineering offices, water companies or project
owners in the design, installation and operation of the ductile iron pipeline systems for water supply:
— introduce practices for design, installation and operation of new ductile iron pipe water supply systems,
rehabilitation or renovation;
— refers to existing standards that specify products’ design, installation and site testing, materials and
coatings.
This document gives efficient support to ISO/TR 7035-1 which indicates chapters here for readers’ reference.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 2531, Ductile iron pipes, fittings, accessories and their joints for water applications
ISO 16631, Ductile iron pipes, fittings, accessories and their joints compatible with plastic (PVC or PE) piping
systems, for water applications and for plastic pipeline connections, repair and replacement
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 2531 and ISO 16631, and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
local main
water main which connects principal main(s) (3.2) with service pipes
3.2
principal main
water main serving as a principal distributor within the supply area, normally without direct consumer
connections
3.3
service pipe
water pipe which supplies water from the local main (3.1) to the consumer

3.4
water distribution system
part of the water supply system comprising pipelines, service reservoirs, pumping stations and other assets
by which water is distributed to the consumers
Note 1 to entry: Note to entry 1: It begins at the outlet from the water treatment works (or source, if there is no
treatment) and ends at the point of connection to the consumer’s installation.
3.5
carrier pipe
pipe inside a casing (3.6), which carries a product such as a gas or liquid
3.6
casing
metal pipe (as well as concrete pipe) used to protect the carrier pipe (3.5)
4 General
Due to its excellent characteristics, the designs and the applications of ductile iron pipe networks for
potable water purpose are quite simple. High mechanical performance (i.e., the robustness) of ductile
iron pipe systems allows energy saving from the reduced mechanisation required during the installation
(no specialized equipment or on-site welding). Similarly, the need for the imported material for bed and
surround is avoided or minimized, with the subsequent saving associated with the unnecessary use of
natural resources and transport costs. Ductile iron pipes do not have the factor of time-dependent material
creep deformation expressed as apparent stiffness as polymeric material pipes do.
Design processes normally start with the design/service objectives, which are related to the characteristics
of the water supply systems in order to meet the targets outlined in Clause 5 and the defined levels of
service (see ISO/TR 7035 -1) over the range of operating conditions, having regards to all relevant economic
considerations and environment and ecology consideration.
5 Practices to set targets for water supplying system
5.1 Water quality
5.1.1 Materials
Almost all the countries or areas have their rules to make all parts of water supply systems in contact with
potable water to be designed and constructed by using components and materials which meet the national
or area stands and regulations, such that there is no unacceptable deterioration on water quality. If that’s
not existing, a practical method is to refer to WHO’s rules.
5.1.2 Prevention of back flow
Potable water supply systems are normally designed, equipped and installed to prevent the back flow. The
air valves and washouts (with their operation and location) are usually used to avoid water entering the
systems. In circumstances of particularly high risk of unacceptable deterioration of water quality, non-
return valves would not be an effective method to prevent the back flow.
5.1.3 Stagnation
Potable water supply systems are principally designed installed and operated to minimize water stagnation
(zones or points) which would lead to unacceptable deterioration of water quality.
The following arrangements are the main points or locations leading to stagnation:
— main with dead ends;
— branch with dead ends;
— spurs serving hydrants;
— un-isolated pipes laid in advance of development;
— sections with permanently low flow rates;
— enhanced pipe diameters required for fire-fighting or other non-permanent purposes.
In practice, facilities (for example, the level invert tees) are usually provided for main flushing.
5.1.4 Cross-connection with other systems
The interconnection of potable water supply systems is possible when the chemical and physical properties
are compatible for blending and there is no unacceptable deterioration of water quality. Normally the potable
water supply systems do not directly connect with the systems containing non-potable water, except a plan
for the blending.
Closed valves or non-return valves, except for air valves, washout and hydrant, normally do not constitute
an effective means of separation for the purpose of the design.
5.2 Design life
Design life follows the requests and needs from the end users or authorities. For ductile iron pipes(buried)
a service life of 100 years is commonly recognized in usual conditions because of the excellent mechanical
properties and good internally and externally anti-corrosion solutions. Normally the design life of ductile
iron pipeline systems is at least 50 years or is based on local national building codes.
Some components such as pumps and certain metering and control equipment are usually replaced earlier
based on the replace time from national regulations.
5.3 Demand for water
5.3.1 General
The total demand of water depends on the elements the pipe systems service for. That includes volume for
resident, factories & plants, municipal use, firefighting. The leakage volume of the pipelines is practically
taken into account also, that depends on the experienced data of leakage ratio.
5.3.2 Water demand estimate
The demand for water depends very much on local circumstances. The real measurement of consumption
makes the estimate results accurate.
In the absence of detail flow measurements or historical data the average daily of demand is practically
obtained by estimating the domestic consumption per person per day (the per capita allowance) and
multiplying it by the number of persons to be supplied. Some local criteria (such as GB 50013) give quota
data helping designing jobs.
Where no better information exists, the overall allowance is usually taken as being between 150 and 250 l
per person per day depending on social and climate conditions excluding specific industrial demands. In
some areas consumption is up to 450 l per person per day.
The demand normally covers other use e.g., street cleaning and supplies to premises such as schools and
hospitals which, added to the per capita allowance, give the overall allowance.
Regarding the peak flow factors, where water use is estimated on an average day basis, suitable factors are
usually applied to give estimates of the expected demand in the peak week, peak day or hour. If no better
information available, the multiplying factor for the peak day usually varies from 1,5 for populations above

10 000, to over two times (the average day demand) for population below2 000. The peak hour rate in any
day ranges from twice the average hour rate in that day for over 10 000 people to more than 5 times the
average for less than 2 000. Where consumer storage is provided, the peak hour flow factors is usually
significantly lower than those experienced data above.
5.3.3 Water for fire-fighting
The potential demand for water for fire-fighting purposes to be provided by the water supply system is very
large in relation with rules from authorities. In these circumstances the authorities responsible for fire-
fighting usually incline to seek alternative sources of emergency supply.
5.4 System security
System security of water supply systems usually includes prevention of acts of vandalism, terrorism or other
unlawful activity.
In general, the underground system will be secure, particular attention is given to above-ground pipework.
Special designs are normally given to pumping station, service reservoirs and other above-gourd
structures, to deter unauthorized entry or interference with operation systems, as well as the possibility
of contamination of potable water. Security fencing and monitoring systems are the practical ways for the
places where risks are higher.
6 Design
6.1 Hydraulic design
6.1.1 Sizing
Mains and service ductile iron pipes are principally sized to meet the maximum specified flow rate having
regard to the defined levels of service. Normally the capacity and flow requirements of the various system
components depends much on the interaction of main, service reservoirs, pumping installations, optimum
hydraulic and economic parameters like pumping cost and asset depreciation. In general, it is the local
mains and principal mains used for direct supply which offer the capacity of sustaining peak flow rates or a
subdivision thereof. Mains that supply reservoir is possible not to meet fully peak flow rates. National rules
usually give the maximum and minimum flow rates. ISO 23991 also gives the experienced data.
In determining the capacity of a reservoir, a practical method is to take the balance between supply and
demand into account. In addition, other aspects are usually considered as following (not limited):
— estimated time to repair bust main upstream;
— effect of pump or power failure;
— existence of alternative sources of supply;
— single or duplicate supply mains to storage;
— degree of telemetry monitoring;
— ratio of peak hour to average flow rate;
— demands with respect to water for industrial supplies, fire-fighting or other special circumstances.

6.1.2 Mains
6.1.2.1 General
Hydraulic calculations are the common jobs for designers to demonstrate that the system will
— satisfy the estimated demand,
— operate at acceptable velocity, and
— operate within the required pressure range.
The designed diameters to satisfy the flow requirements for the hydraulic gradient are calculated by widely
known calculation methods as follow in this clause.
The inner diameter of the pipe has a major influence on the pressure loss and therefor on the pumping
energy consumptions. The greater internal diameter of the ductile iron pipe in comparison to the equivalent
nominal diameter provides better economic results.
6.1.2.2 Head loss
It’s widely known that the total head loss of a pipeline is as following (Formula 1):
HH=+H (1)
tf l
where
H is the total head loss, in meters;
t
H is the friction head loss, in meters;
f
H is the local head loss, in meters.
l
The H is calculated by different methods known as Hazen-William’s formula, Darcy-Wisbach formula and
f
Chezy formula. These formulae are well known by designers globally, and ISO 23991 gives some of them.
6.1.2.3 Local head loss
Local head loss mainly occurs at bends, tees, valves and other service connections, as well as the irregularities
in the ductile iron pipeline profile. It is usually taken into account in two ways:
— using experimental results which demonstrate the head losses are approximately proportional to the
square of flow velocity, as the Formula 2 shows. Coefficients are available for various types of fittings;
— using an ‘equivalent length’ of straight pipe to give the same loss of head as the fittings. Some local criteria
define k the hydraulic roughness to be 0,1 mm as a reasonable value for distribution mains instead of
being 0,03 for straight ductile iron pipelines.
V
H =∑ξ× (2)
l
2g
Where
H is the local head loss in metres;
l
ξ
is the coefficient for local head loss, which depends on the shape of fittings, flowing direction;
V is the flow velocity in metres per second;
g is the gravity acceleration in metres per square second.

Some experienced local head loss coefficients for different type fittings or points are available in published
documents (such as ‘Handbook of Hydraulic Calculation”).
6.1.2.4 Flow velocities
Following aspects practically affect the acceptable flow velocities:
— stagnation;
— turbidity;
— pressure;
— surge;
— pumping facilities.
In practice, it is desirable to avoid unduly high or low velocities. The range from 0,5 m/s to 2,0 m/s is
considered appropriate. For pumping mains, a financial appraisal is usually undertaken to determine the
most economic diameter to minimize the capital and discount pumping cost. The resulting velocity normally
lies in range of 0,8 m/s to 1,4 m/s.
6.1.3 Local main
Local mains are designed to meet estimated peak flow rates. That means the capacity of local main is
adequate to convey additional flows for fire-fighting in accordance with national or local requirements.
6.1.4 Service pipes
6.1.4.1 Domestic consumers
The diameter of service pipes for domestic purpose is usually determined on the basis of the level of service
requirements’ including service pressure and flow rate. Head losses through all components including
fittings and meters is normally taken into consideration.
6.1.4.2 Non domestic consumers
The service pipe diameter is determined on the basis of the requirements of the consumer as agreed with
the water supplier.
6.1.4.3 Fire - fighting
The diameters of pipes for fire-fighting normally refer to the local regulations or rules from authorities.
6.2 Structural design
ISO 10803 gives the structural design of buried ductile iron pipelines.
6.3 System layout design
6.3.1 Mains
The layout of ductile iron mains depends much on the local circumstances. The consideration practically
includes:
— reliability of supply;
— good access for maintenance;
— provision and location of line valves, air valves, washout and hydrants;

— adverse ground conditions and difficult terrain;
— risk of damage to and from plants/trees and their roots;
— corrosion protection systems in aggressive or contaminated soils;
— minimum gradient (minimum gradient normally is 1/500);
— crossing roads, rivers, railways, existing constructions;
— adoption of shortest practical route;
— location of other services, buildings and structures;
— telemetry, control and metering;
— all design pressures;
— earth loads and traffic loads;
— ease of operation;
— national and local planning, environmental protection;
— depth of frost penetration;
— risk of damage to and from utilities, works and apparatus;
— the minimum distance between existing/planned service, to follow the local criteria;
— minimum depth of cover for buried pipes;
— maximum depth of cover for ease of repair.
Whenever possible mains are normally located to allow easy vehicular access for repair and maintenance.
Mains running parallel to or cross foul of combination sewers are normally located at higher levels. If this is
not possible, adequate precautions are taken to preclude ingress of contaminated water to the main.
6.3.2 Service pipes
The location and depth of service pipes normally follows the same practice as for the mains.
The service pipes are normally planned to be as straight as possible following the shortest route from the
local main to the buildings.
6.3.3 Valves
Valves including air valve, drain valve, isolation valve, hydrant and surging limitation equipment are integral
components of a pipeline systems. ISO 21051 gives the detail instruction about layout and installation of
them, some local criteria also offer similar information.
6.3.4 Reservoirs
Some reservoirs for example water towers are usually designed in the ductile iron pipeline systems. They
are designed, constructed and tested to provide the required security to supplies, at same time not to make
any unacceptable deterioration in the quality of the stored water.
6.3.5 Pump stations
Design of plant arrangements and pump duties for complex systems are usually based on detailed studies
using simulation and optimization techniques. Control systems, actuated by pressure, flow, level or time,
depend on local conditions and can be manual or fully automatic with telemetry monitoring. Safeguards
are usually taken to incorporate in pump controls to stop units in the event of loss of suction pressure, or

unacceptable flow conditions. The major function of control systems is to ensure that unnecessary repeated
stopping/starting or speed changes are prevented.
Practically, pumping units are designed to prevent the following conditions:
— cavitation;
— instability (abnormal fluctuation between different rates of flow);
— overloading (abnormal increase in power consumption).
6.4 Protection against aggressive environment
6.4.1 General
Ductile iron pipes are normally delivered externally and internally coated. These coatings(external)
and linings (internal) make them to pass through in a wide range of external and internal environments.
Evaluation of the different corrosion risks (corrosivity of the soil, stray currents, aggressive waters, etc.) into
which the proposed pipeline to be installed is a major step to select the appropriate protection for the pipes.
6.4.2 External protection
Ductile iron pipeline systems are normally buried in contact with the majority of soils. Followings are the
main factors to evaluate the aggressivity of external operating environments:
— resistivity;
— pH;
— water table level;
— stray currents;
— corrosion cells;
— soil contamination (industrial effluents, wastes, etc).
Metallic zinc-based coatings are suitable for the majority of the soils. Alternative coatings are available for
highly corrosive soils or specific environments. Detailed lists of the different existing coatings, with their
field of use, are given in ISO 2531, ISO 8179-1 and ISO 8179-2. Some local criteria (such as EN 545) also give
similar indications.
Repairs to the pipe coatings at faults are usually specified by the designer in accordance with the product
standards or ISO 21051, taking into account the manufacturer’s instructions.
6.4.3 Internal protection
Ductile iron pipeline systems are used to convey a wide range of potable waters. The followings are main the
factors to evaluate the aggressivity of potable waters:
— pH;
— sulfates;
— magnesium;
— ammonium;
— aggressive CO .
Cement linings according to ISO 4179 are suitable for the majorities of potable waters. Alternative linings for
pipes or fittings are given in ISO 2531 and ISO 24131 series or local criteria (such as EN 545). An evaluation
method of water aggressiveness and optimal choices for internal linings is given in ISO TR 4340.
7 Hydraulic thrust restraint design
7.1 Hydraulic thrust force and restraint principles
ISO 21052 gives details of hydraulic thrust forces and restraint principles. Practically there are two methods
to restrain the thrust: blocks solution and restrained joints solution.
7.2 Thrust blocks solutions
Use of concrete thrust/anchor blocks is the most common applied technique for containing the hydraulic
thrust of socket and spigot mains under pressure. But it’s use is now sharply decline.
Various type of concrete thrust/anchor blocks are designed for this solution, depending on the configuration
of the main, the strength and type of soil, the presence or absence of ground water. The block contains the
hydraulic thrust forces by friction on the soil or/and by bearing against the ground. In practice, thrust /
anchor blocks are designed by taking into account both the friction forces and the soil reaction against
their bearing surface. Bearing surface of concrete block is normally placed against undisturbed soil where
possible.
Where it is not possible, the fill between the bearing surface and undisturbed soil is compacted to at least
90 % Standard Proctor density. Block height is usually designed to be equal to or less than one-half the
total depth to the bottom of the block, and not less than the pipe diameter. The width of block is usually
designed to be between one and two times the height of the block. The volume & dimensions of blocks can be
calculated following national standards and/or the catalogues of ductile iron pipe suppliers.
Figure 1 is the diagram of a thrust block combining with a bend.
Figure 1 — Diagram of a thrust block combining with a bend
7.3 Restrained joints solution
7.3.1 General
Anchoring technologies (e.g., restrained joints or anchored joints) are increasingly taking the place of
concrete anchor blocks which have some shortages including their weight and size. For example, the space
demands on work sites for large diameter of pipelines, the time spent on trench opening and hardening, as
well as the risk of long-term destabilization.

The utilization of restraint/anchoring joint is growing fast in most counties all over the wo
...