BS EN
BRITISH STANDARD
806-3:2006
Specifications for
installations inside
buildings conveying
water for human
consumption 
Part 3: Pipe sizing  Simplified method
The European Standard EN 806-3:2006 has the status of a
British Standard
ICS 91.140.60

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BS EN 806-3:2006
National foreword
This British Standard is the official English language version of
EN 806-3:2006. This part of BS EN 806 partially supersedes BS 6700:1997. On
publication of parts 1 to 5 of BS EN 806, BS 6700:1997 will be withdrawn.
NOTE EN 806 parts 1 to 5 have been agreed by CEN to be a  package with a common Date of
Withdrawal for conflicting National Standards (Resolution CEN/BT/20/1993 and CEN/TC 164
Resolution 199 refer).
The UK participation in its preparation was entrusted by Technical Committee
B/504, Water supply, to Subcommittee B/504/2, Domestic installation design 
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This British Standard was
Amendments issued since publication
published under the authority
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Amd. No. Date Comments
Strategy Committee
on 28 April 2006
� BSI 2006
ISBN 0 580 48283 9
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EUROPEAN STANDARD
EN 806-3
NORME EUROP�ENNE
EUROP�ISCHE NORM
April 2006
ICS 91.140.60
English Version
Specifications for installations inside buildings conveying water
for human consumption - Part 3: Pipe sizing - Simplified method
Sp�cifications techniques relatives aux installations d'eau Technische Regeln f�r Trinkwasser-Installationen -
destin�e ą la consommation humaine ą l'int�rieur des Berechnung der Rohrinnendurchmesser - Teil 3:
b�timents - Partie 3: Calculations des diamŁtres int�rieurs - Vereinfachtes Verfahren
M�thode simplifi�e
This European Standard was approved by CEN on 3 February 2006.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Central Secretariat or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania,
Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMIT� EUROP�EN DE NORMALISATION
EUROP�ISCHES KOMITEE F�R NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
� 2006 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 806-3:2006: E
worldwide for CEN national Members.
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EN 806-3:2006 (E)
Contents
Page
Foreword......................................................................................................................................................................3
1 Scope ..............................................................................................................................................................4
2 Normative references ....................................................................................................................................4
3 Terms, symbols and units ............................................................................................................................4
4 Principles of pipe sizing calculations..........................................................................................................5
5 Simplified method of pipe sizing..................................................................................................................6
6 Special-installations ......................................................................................................................................8
Annex A (informative) Example for the determination of pipe sizes for standard-installations .......................9
Annex B (informative) Design flow rates in relation to total flow rates .............................................................12
Annex C (informative) List of national pipe sizing methods ...............................................................................14
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EN 806-3:2006 (E)
Foreword
This European Standard (EN 806-3:2006) has been prepared by Technical Committee CEN/TC 164  Water
supply , the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an identical text or
by endorsement, at the latest by October 2006, and conflicting national standards shall be withdrawn at the latest
by October 2006.
NOTE This is the third part of the European Standard (EN 806) consisting of five parts as follows:
Part 1: General
Part 2: Design
Part 3: Pipe sizing
Part 4: Installation
Part 5: Operation and maintenance
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark,
Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United
Kingdom.
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EN 806-3:2006 (E)
1 Scope
This European Standard is in conjunction with EN 806-1 and EN 806-2 for drinking water systems within premises.
This European Standard describes a calculation method for the dimensioning of pipes for the type of drinking water
standard-installations as defined in 4.2.
It contains no pipe sizing for fire fighting systems.
2 Normative references
The following referenced documents are indispensable for the application 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.
EN 806-1, Specifications for installations inside buildings conveying water for human consumption  Part 1:
General
EN 806-2, Specifications for installations inside buildings conveying water for human consumption  Part 2:
Design
3 Terms, symbols and units
This Clause is enlarged in completion to EN 806-1, to have in the field of pipe sizing the same definitions in
European standards.
Table 1  Terms and definitions
Term Symbol Unit Explanation (definition)
Flow-velocity v m/s
Flow-rate, volume flow Q l/s Ratio of the volume of water passing through a specified flow
m3/h cross-section and the time required for this
Minimum flow-rate at draw-off point Qmin l/s Flow-rate at draw-off point which is just sufficient for the
appliance to function
Draw-off flow-rate Q l/s Assumed draw-off flow-rate at appliance for calculation
A
purposes
Total flow-rate Q l/s Ł Q , sum of all draw-off flow-rates of the water appliances
T A
supplied
Design flow-rate Q l/s Flow-rate for hydraulic calculations, taking into consideration
D
the probable simultaneous demand
Static pressure p Pa Gauge pressure at a measuring point in the water supply
R
system when no water flowing
Flow pressure p Pa Gauge pressure at a measuring point in the water supply
Fl
system when water flowing
Minimum flow pressure p Pa Gauge pressure required at the connection to a draw-off point
minFl
at its draw-off flow-rate
Pressure difference, head loss "p Pa Difference in pressure between two points in the drinking water
installation, resulting from wall friction and individual head loss
(To be continued)
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EN 806-3:2006 (E)
Table 1 (concluded)
Term Symbol Unit Explanation (definition)
Head loss as a consequence of difference "pe Pa -
in elevation
Pipe length I m -
Internal diameter of pipe di mm -
External diameter of pipe d mm -
a
Wall thickness of pipe s mm -
Loading unit LU 1 Factor taking into account the flow-rate required at an
appliance, the length of time the appliance is in use and the
frequency of use. One loading unit (1 LU) equalises a draw-off
flow rate Q of 0,1 l/s.
A
4 Principles of pipe sizing calculations
4.1 General
Pipe sizing takes into consideration the character of the installation, the pressure conditions and the flow velocities.
This part includes the underground pipes within the premises.
4.2 Characters of installations
In a building there are standard-installations and special-installations.
An installation can be called a standard-installation, when:
" the draw off flow rates do not exceed those set out in Table 2;
" the kind of demand does not exceed the design flow-rate as shown in Figure B.1 (see Annex B);
" it is not designed for continuous use of water. Continuous use being defined as use lasting more than
15 min.
Other installations are called special-installations.
4.3 Pressure conditions
Static pressure at draw off point max. 500 kPa
(Exception: garden/garage taps max. 1 000 kPa);
Flow pressure at draw off point min. 100 kPa.
Several draw off points, e.g. thermostatic mixing valves, need a higher flow pressure. Calculations have to consider
this matter.
The difference between the static pressure at the lowest draw off point and the flow pressure at the hydraulic worst-
case draw off point, reduced by the pressure losses (resulting from wall frictions and individual head losses), give
the possible head of difference in elevation within a pressure section.
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EN 806-3:2006 (E)
4.4 Maximum flow velocities
The figures given in Table 3 are based on the following flow velocities:
header pipes, rising pipes, floor service pipes max. 2,0 m/s;
connection pipes to one fitting (dead legs) max. 4,0 m/s.
NOTE National regulations may require lower flow velocities to avoid water hammer and noise.
5 Simplified method of pipe sizing
5.1 General
This clause shows a possibility for a simplified pipe sizing for standard-installations. This method can be used for all
type of buildings, which do not have measurements, which highly exceed the average. That means that in most of
the buildings the simplified method can be applied.
This method is equally used for cold and for hot water pipes.
5.2 Detailed calculations
The designer is free to use a nationally approved detailed calculation method for pipe sizing (see Annex C).
5.3 Hot water return pipes
As hot water return pipes have to fulfil other hydraulic requirements, they cannot be sized with this method. The
flow-velocity in the hot water return pipes shall be calculated according to national or manufacturer s
recommendation.
5.4 Loading unit
1 loading unit (LU) is equivalent to a draw-off flow rate QA of 0,1 l/s.
Table 2  Draw-off flow-rates QA , minimum flow-rates at draw-off points Qmin and loading units for draw-
off points
Draw-off point Q Q Loading units
A min
l/s l/s
Washbasin, handbasin, 0,1 0,1 1
bidet, WC-cistern
Domestic kitchen sink, - 0,2 0,15 2
a
washing machine , dish
washing machine, sink,
shower head
Urinal flush valve 0,3 0,15 3
Bath domestic 0,4 0,3 4
Taps /garden/garage) 0,5 0,4 5
Non domestic kitchen sink 0,8 0,8 8
DN 20, bath non domestic
Flush valve DN 20 1,5 1,0 15
a
For non domestic appliances check with manufacturer.
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EN 806-3:2006 (E)
The values in this Table do not correspond with the values in product norms. They are only used for pipe sizing.
5.5 Application of the simplified method
Beginning at the last draw-off point, the loading units for each section of the installation have to be determined. The
loading units must be added. The probability of simultaneous demand has been taken into consideration in Tables
3.1 to 3.8. Depending on the material chosen by the designer the pipe size can now be taken out of Tables 3.1 to
3.8. The design flow-rate QD as given in Figure B.1 is taken into account for the values in Tables 3.1 to 3.8.
Table 3  Loading units for determination of pipe diameters
Table 3.1  Hot-dip galvanised steel
Max. load LU 6 16 40 160 300 600 1 600
Highest value LU 4 15
DN 15 20 25 32 40 50 65
d mm 16 21,6 27,2 35,9 41,8 53 68,8
i
Max length of m 10 6
pipe
Table 3.2  Copper
Max. load LU 1 2 3 3 4 6 10 20 50 165 430 1 050 2 100
Highest value LU 2 4 5 8
da x s mm 12 x 1,0 15 x 1,0 18 x 1,0 22 x 1,0 28 x 1,5 35 x 1,5 42 x 1,5 54 x 2 76,1 x 2
d mm 10,0 13,0 16,0 20,0 25 32 39 50 72,1
i
Max length of m 20 7 5 15 9 7
pipe
Table 3.3  Stainless steel
Max. load LU 3 4 6 10 20 50 165 430 1 050 2 100
Highest value LU 4 5 8
d x s mm 15 x 1,0 18 x 1,0 22 x 1,0 28 x 1,2 35 x 1,5 42 x 1,5 54 x 1,5 76,1 x 2
a
d mm 13,0 16,0 19,6 25,6 32 39 51 72,1
i
Max length of pipe m 15 9 7
Table 3.4  PE-X
Max. load LU 1 2 3 4 5 8 16 35 100 350 700
Highest value LU 4 5 8
d x s mm 12 x 1,7 16 x 2,2 20 x 2,8 25 x 3,5 32 x 4,4 40 x 5,5 50 x 6,9 63 x 8,6
a
d mm 8,4 11,6 14,4 18,0 23,2 29 36,2 45,6
i
Max length of pipe m 13 4 9 5 4
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EN 806-3:2006 (E)
Table 3 (concluded)
Table 3.5  PB
Max. load LU 1 2 3 3 4 6 13 25 55 180 500 1 100
Highest value LU 2 4 5 8
da x s mm 12 x 1,3 16 x 1,5 20 x 1,9 25 x 2,3 32 x 3 40 x 3,7 50 x 4,6 63 x 5,8
di mm 9,4 13,0 16,2 20,4 26 32,6 40,8 51,4
Max length of pipe m 20 7 5 15 9 7
Table 3.6  PP
Max. load LU 1 2 3 3 4 6 13 30 70 200 540 970
Highest value LU 2 4 5 8
da x s mm 16 x 2,7 20 x 3,4 25 x 4,2 32 x 5,4 40 x 6,7 50 x 8,4 63 x 10,5 75 x 12,5
di mm 10,6 13,2 16,6 21,2 26,6 33,2 42 50
Max length of pipe m 20 12 8 15 9 7
Table 3.7  PVC-C
Max. load LU 3 4 5 10 20 45 160 420 900
Highest value LU 4 5 8
da x s mm 16 x 2,0 20 x 2,3 25 x 2,8 32 x 3,6 40 x 4,5 50 x 5,6 63 x 6,9
di mm 12,0 15,4 19,4 24,8 31 38,8 49,2
Max length of pipe m 10 6 5
Table 3.8  PEX/AL/PE-HD resp. PE-MD/AL/PE-HD
Max. load LU 3 4 5 6 10 20 55 180 540 1 300
Highest value LU 4 5 5 8
da x s mm 16 x 2,25/16 x 2,0 18 x 2 20 x 2,5 26 x 3 32 x 3 40 x 3,5 50 x 4 63 x 4,5
di mm 11,5/12,0 14 15 20 26 33 42 54
Max length of pipe m 9 5 4
For materials not mentioned in the tables, the table with the most similar material and in this table the column with
the most similar or equal diameter shall be chosen.
6 Special-installations
Special-installations are installations, which do not fulfil the conditions for standard-installations or if the building
has measurements, which highly exceed the average.
There are installations, where only parts of the project shall be called special-installations. In these cases the parts
which fulfil the conditions for standard-installations can be sized with the simplified method.
Pipes for special-installations shall be sized by nationally approved detailed calculations (see Annex C).
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EN 806-3:2006 (E)
Annex A
(informative)
Example for the determination of pipe sizes for standard-installations
Figure A.1  Example for standard-installation
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EN 806-3:2006 (E)
Appliance
Beginning at the end of the pipe the loading units must be added. Resulting from this calculation the size of that
part of the pipe can be determined.
Task according to the drawing
The cold water pipe from the under ground floor to the draw-off points has to be sized.
The pipe shall be in hot-dip galvanised steel.
In every apartment the following draw-off points will be installed:
1 domestic bath
1 WC-cistern
1 washbasin
1 domestic kitchen sink
There are five equal apartments.
Result
Find the loading units from Table 2:
1 domestic bath 4 LU
1 WC-cistern 1 LU
1 washbasin 1 LU
1 domestic kitchen sink 2 LU
Part 1
connected is 1 domestic kitchen sink = 2 LU
Table 3.1 demands for 2 LU = DN 15
Part 2
connected are 1 domestic kitchen sink = 2 LU
1 domestic bath = 4 LU
total = 6 LU
Table 3.1 demands for 6 LU = DN 15
Part 3
connected are 1 domestic kitchen sink = 2 LU
1 domestic bath = 4 LU
1 washbasin = 1 LU
total = 7 LU
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EN 806-3:2006 (E)
Table 3.1 demands for 7 LU = DN 20
Part 4
connected are 1 domestic kitchen sink = 2 LU
1 domestic bath = 4 LU
1 washbasin = 1 LU
1 WC-cistern = 1 LU
total per apartment = 8 LU
Table 3.1 demands for 8 LU = DN 20
Part 5
connected are 2 apartments = 16 LU
Table 3.1 demands for 16 LU = DN 20
Part 6
connected are 3 apartments = 24 LU
Table 3.1 demands for 24 LU = DN 25
Part 7
connected are 4 apartments = 32 LU
Table 3.1 demands for 32 LU = DN 25
Part 8
connected are 5 apartments = 40 LU
Table 3.1 demands for 40 LU = DN 25
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EN 806-3:2006 (E)
Annex B
(informative)
Design flow rates in relation to total flow rates
The diagram (Figure B.1) shows a possibility to determine the design flow-rate QD from Ł LU for standard-
installations. Where nationally approved further such diagrams (e.g. for various types of buildings) may be used.
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EN 806-3:2006 (E)
Key
1 Design flow rate Q D
2 Total flow rate Q T in LU
3 Example of highest single value LU
Figure B.1  Design flow rate Q D in l/s for standard-installations in relation to the total flow rate Q T in LU
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EN 806-3:2006 (E)
Annex C
(informative)
List of national pipe sizing methods
The following survey gives information about existing national calculation methods which can be used as an
alternative to this European Standard or in cases where reasons for differentiated pipe sizing are given e.g. for big
buildings, industrial and commercial plants etc. If any other national calculation methods exist, which are not listed
here, it is recommended that the national standardization body should give information in the foreword of the
national edition of EN 806-3.
Table C.1  National pipe sizing methods
Country Document No Title
Austria �NORM B 2531-2 Trinkwasserversorgungseinrichtungen in
Grundst�cken; Bemessung der Rohrleitungen
Denmark DS 439 Code of Practice for domestic water supply installations
Finland National Building Code of Water supply and drainage installations for buildings 
Finland, D1 Regulations and recommendations 1987
France NF P40-202 RŁgles de calcul des installations de plomberie sanitaire et des
(ref DTU 60.11) installations d'�vacuation des eaux pluviales
Germany DIN 1988-3 Technische Regeln f�r Trinkwasser-Installationen (TRWI);
Ermittlung der Rohrdurchmesser; Technische Regel des DVGW
The Netherlands VEWIN Working Sheets
WB 2.1 Principles of calculation: General and overview
WB 2.1 A Principles of calculation: Flow rate and working pressures for
tapware and apparatus
WB 2.1 C Principles of calculation: Calculation and design criteria
WB 2.1 G Principles of calculation and tables for determining pressure
losses in pipes
Spain Código T�cnico de la Suministro de agua
Edificatión, Sección HS4 Abastecimiento de agua. Dimensionamiento de instalaciones
PNE 149201 interiores de agua
United Kingdom BS 6700:1997 Specification for design, installation, testing and maintenance of
services supplying water for domestic use within buildings and
their curtilages
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