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© The British Standards Institution 2025

Published by BSI Standards Limited 2025

ISBN 978 0 539 12481 1

ICS 13.060.25

The following BSI references relate to the work on this document:
Committee reference EH/3
Drafts for comment 21/30408387 DC; 23/30480279 DC; 25/30513118 DC

Foreword

Publishing information

This British Standard is published by BSI Standards Limited, under licence from The British Standards Institution, and came into effect on 30 September 2025. It was prepared by Technical Committee EH/3, Water quality. A list of organizations represented on this committee can be obtained on request to the committee manager.

Information about this document

Users of this British Standard are advised to consider the desirability of using components that have been demonstrated by third-party assessment to be suitable.

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Use of this document

As a code of practice, this British Standard takes the form of guidance and recommendations. It should not be quoted as if it were a specification and particular care should be taken to ensure that claims of compliance are not misleading.

Any user claiming compliance with this British Standard is expected to be able to justify any course of action that deviates from its recommendations.

Presentational conventions

The provisions of this standard are presented in roman (i.e. upright) type. Its recommendations are expressed in sentences in which the principal auxiliary verb is “should”.

Commentary, explanation and general informative material is presented in smaller italic type, and does not constitute a normative element.

Where words have alternative spellings, the preferred spelling of the Shorter Oxford English Dictionary is used (e.g. “organization” rather than “organisation”).

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

Particular attention is drawn to the following specific regulations:

The Water Supply (Water Fittings) Regulations 1999 [1]
The Water Supply (Water Fittings) Regulations (Northern Ireland) 2009 [2]
The Water Supply (Water Fittings) (Scotland) Byelaws 2014 [3]
The Health and Safety at Work, etc. Act 1974 [4]
The Control of Substances Hazardous to Health Regulations 2002 [5]
The Building Regulations 2000, as amended (particularly Approved Document L1) [6]
The Building (Scotland) Regulations 2004 [7]
The Building Regulations (Northern Ireland) Statutory Rules 2000 [8]
The Trade Effluent (Prescribed Processes and Substances) Regulations 1989 [9]
The Hazardous Waste (England and Wales) Regulations 2005 [10]
The Special Waste Regulations 1996 [11]
The Hazardous Waste (Wales) Regulations 2005 [12]
The Hazardous Waste Regulations (Northern Ireland) 2005 [13]

Introduction

In order to promote the longevity of pipework and plant, and to minimize energy consumption, it is important to design systems for ease of cleaning, select materials that minimize the risk of ongoing corrosion and clean the systems effectively. It is important that systems are designed to minimize the ingress of oxygen to reduce the risk of corrosion damage, and for water conditions to be validated on completion of the work.

This British Standard aims to assist system designers and specifiers, project managers and installers, and can be read in conjunction with BS 7593. BS 8693 relates to newly installed systems:

offering advice to designers and specifiers for closed water systems;
offering advice for installers of closed systems; and
clarifying requirements for record keeping and validation of water quality at handover or practical completion.

The standard is not applicable to the cleaning of systems after they have been put into regular use after handover or practical completion. The type of debris present in new systems differs from contaminants in existing operational systems. However, if system design or installation is poor, this can impact on the outcome of remedial cleaning on fouled operational systems.

1 Scope

This British Standard gives recommendations for the design and installation of new build construction incorporating systems circulating water in sealed heating and cooling systems prior to their handover to developers.

This British standard gives recommendations for:

the design and preparation of pipework and plant, laying the foundations for stable water conditions;
the removal of construction related debris before the heat/cooling source is available;
validation methods and records to accompany the handover of new systems; and
good practices to promote the quality, longevity and efficiency essential for successful operation of the systems.

This British Standard is relevant to systems in an individual residential dwelling or within a commercial enterprise, residential development or indirectly connected to a district heating and cooling system. It applies to individual heating and cooling circuits in single or multiple residential premises with a maximum system volume of nominally less than 250 l.

This British Standard does not cover the lifetime maintenance of the systems, or remedial work or upgrades to operational systems. It also does not apply to commercial multiple residential premises served by one common circuit.

This British Standard is relevant to system designers, specifiers, installers, project managers and water treatment companies.

NOTE 1 For specialized closed circuits, such as those containing solar thermal panels and ground source heat pump loops, refer to the manufacturer’s instructions. See also BS 5918 (for solar thermal) and MIS 3005 [14] (for ground source heat pumps).

NOTE 2 For larger closed systems (>250 l) such as those found in commercial or municipal premises, or the primary/ secondary systems on residential developments, refer to BSRIA BG 29 Pre-Commission Cleaning of Pipework Systems [N1].

NOTE 3 Where cleaning is referred to in this document it is intended that it refers to the removal of manufacturing debris and residues, engineering residues, such as cutting swarf, solder and flux, and mill scale and incidental debris created during the construction of a system. For the removal of operational contaminants (e.g. limescale), see BS 7593.

2 Normative references

3 Terms, definitions and symbols

3.1 Terms and definitions

3.2 Symbols

4 System design and installation

4.1 Accessibility and maintainability

4.2 Protection for sensitive plant and terminal units

4.3 Heating and cooling sources flushing facilities

4.4 Dynamic flushing flow measurement

4.5 Use of strainers

4.6 Dosing facilities

4.7 Drainage facilities

5 Materials of construction

6 Filling/flushing water supply

7 Initial filling of systems and expansion vessels

7.1 Filling

7.2 Pressure testing

8 Make-up water to systems that are in operation

8.1 General

8.2 System fill water supply

8.3 Sealed systems

8.4 Open vented recirculating systems

9 Microbiological control prior to cleaning

10 Pre-commission cleaning methodologies

10.1 Introduction

Pre-commission cleaning of new closed systems should be undertaken to provide the longevity and efficiency of the system.

NOTE 1 BS 7593 outlines the procedures for cleaning new systems and systems requiring cleaning after handover and practical completion.

NOTE 2 Debris and fouling within the system not only reduces the life of the system but can also cause sensitive equipment, such as control valves and PICVs, to fail.

NOTE 3 Filled pipework and terminal units left stagnant can lead to deterioration of water quality and the formation of biofilm and bacterial fouling. The presence of debris and/or biofilm can reduce the efficiency of heat transfer or block water ways.

Automatic control of control valves or PICVs should be overridden into the “open” position, and TRV heads should be replaced by manual control heads with valves overridden into the “open” position prior to commencement of cleaning. Radiators should be bypassed to keep them dry while pipework is cleaned.

NOTE 4 See Figure 5 and Figure 6 for more information.

The design and installation should facilitate effective cleaning.

NOTE 5 For more information, see Annex B.

10.2 Temporary pumps

10.3 Flushing and cleaning

10.4 Water quality specifications

11 Validation of water condition

11.1 General

11.2 Validation criteria

11.3 Sampling and analysis plan

11.4 Water quality parameters

12 Mothballing/maintaining water quality until handover

13 Handover documents

Bibliography

BS 8693:2025

Water treatment for small volume heating and cooling systems in residential dwellings (including apartments). Design, installation, handover and validation. Code of practice

Current

Published:

26 Sep 2025