EN 16941-1:2018

On-site non-potable water systems - Part 1: Systems for the use of rainwater

This European Standard specifies the requirements and gives recommendations for the design, sizing, installation, identification, commissioning and maintenance of rainwater harvesting systems for the use of rainwater on-site as non-potable water. This European Standard also specifies the minimum requirements for these systems.
Excluded from the scope of this European Standard are:
- the use as drinking water and for food preparation;
- the use for personal hygiene purposes;
- decentralized attenuation;
- infiltration.
NOTE   Conformity with the standard does not exempt from compliance with the obligations arising from local or national regulations.

Vor-Ort-Anlagen für Nicht-Trinkwasser - Teil 1: Anlagen für die Verwendung von Regenwasser

Diese Europäische Norm legt Anforderungen fest und enthält Empfehlungen für Planung, Bemessung, Einbau, Kennzeichnung, Inbetriebnahme und Wartung von Regenwassernutzungsanlagen zur Verwendung von Regenwasser vor Ort. Diese Europäische Norm legt auch die Mindestanforderungen an solche Systeme fest.
Vom Anwendungsbereich dieser Europäischen Norm ausgenommen sind:
   die Verwendung als Trinkwasser und zur Herstellung von Speisen;
   die Verwendung für die Körperhygiene;
   dezentrale Rückhaltung;
   Infiltration.
ANMERKUNG Konformität mit dieser Norm entbindet nicht von der Einhaltung der Auflagen, die sich aus örtlichen oder nationalen Vorschriften ergeben können.

Réseaux d’eau non potable sur site - Partie 1 : Systèmes pour l’utilisation de l’eau de pluie

La présente Norme européenne spécifie les exigences et fournit des recommandations concernant la conception, le dimensionnement, l’installation, l’identification, la mise en service et l’entretien des systèmes de récupération de l’eau de pluie pour son utilisation sur site en tant qu’eau non potable. La présente Norme européenne spécifie également les exigences minimales relatives à ces systèmes.
Sont exclues du domaine d’application de la présente Norme européenne :
-   l’utilisation comme eau potable et pour la préparation des aliments ;
-   l’utilisation pour l’hygiène personnelle ;
-   le stockage et la restitution à débit contrôlé ;
-   l’infiltration.
NOTE   La conformité à la présente norme ne dispense pas de se conformer aux obligations découlant des réglementations nationales ou locales.

Sistemi za vodo, ki ni namenjena pitju, nameščeni na terenu - 1. del: Sistemi za uporabo deževnice

Ta evropski standard določa načrtovanje, ugotavljanje velikosti, namestitev, prepoznavanje, zagon in vzdrževanje sistemov za zbiranje deževnice za njeno uporabo na terenu kot nadomestek za pitno vodo. Standard prav tako določa minimalne zahteve za te sisteme.
Ta standard ne zajema:
– uporabe pitne vode,
– decentraliziranega zmanjševanja odtoka vode,
– infiltracije.
OPOMBA: Skladnost s standardom ne pomeni, da lahko uporabnik opusti ukrepe za izpolnitev zahtev, ki izhajajo iz lokalnih ali nacionalnih predpisov.

General Information

• Status: Withdrawn
• Publication Date: 23-Jan-2018
• Withdrawal Date: 13-Apr-2025
• ICS: 93.025 - External water conveyance systems
• Technical Committee: CEN/TC 165 - Waste water engineering
• Drafting Committee: CEN/TC 165/WG 50 - Use of treated wastewater
• Current Stage: 9960 - Withdrawal effective - Withdrawal
• Start Date: 20-Mar-2024
• Completion Date: 14-Apr-2025
• Ref Project: SIST EN 16941-1:2018 - On-site non-potable water systems - Part 1: Systems for the use of rainwater

Relations

• Replaced By: EN 16941-1:2024 - On-site non-potable water systems - Part 1: Systems for the use of rainwater
• Effective Date: 18-Jan-2023

Standards Content (Sample)

SLOVENSKI STANDARD
01-marec-2018
6LVWHPL]DYRGRNLQLQDPHQMHQDSLWMXQDPHãþHQLQDWHUHQXGHO6LVWHPL]D
XSRUDERGHåHYQLFH
On-site non-potable water systems - Part 1: Systems for the use of rainwater
Vor-Ort Anlagen für Nicht-Trinkwasser - Teil 1: Anlagen für die Verwendung von
Regenwasser
Réseaux d’eau non potable sur site - Partie 1 : Systèmes pour l’utilisation de l’eau de
pluie
Ta slovenski standard je istoveten z: EN 16941-1:2018
ICS:
93.025 Zunanji sistemi za prevajanje External water conveyance
vode systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 16941-1
EUROPEAN STANDARD
NORME EUROPÉENNE
January 2018
EUROPÄISCHE NORM
ICS 93.025
English Version
On-site non-potable water systems - Part 1: Systems for
the use of rainwater
Réseaux d'eau non potable sur site - Partie 1 : Systèmes Vor-Ort-Anlagen für Nicht-Trinkwasser - Teil 1:
pour l'utilisation de l'eau de pluie Anlagen für die Verwendung von Regenwasser
This European Standard was approved by CEN on 28 August 2017.

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 CEN-CENELEC Management Centre 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 CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 16941-1:2018 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Functional elements of rainwater harvesting systems . 8
5 Design . 8
5.1 Collection . 8
5.1.1 General . 8
5.1.2 Collection surfaces . 9
5.1.3 Collection piping system . 9
5.2 Treatment . 9
5.2.1 General . 9
5.2.2 Preliminary treatment . 10
5.2.3 Additional treatment . 10
5.3 Storage . 10
5.3.1 General . 10
5.3.2 Materials . 11
5.3.3 Dimensions . 11
5.3.4 Capacity. 11
5.3.5 Structural behaviour . 11
5.3.6 Watertightness . 11
5.3.7 Connections and internal pipe system . 11
5.3.8 Access . 12
5.3.9 Overflow . 12
5.4 Back-up water supply . 12
5.4.1 General . 12
5.4.2 Backflow protection device . 13
5.5 Pumping . 14
5.5.1 General . 14
5.5.2 Submerged pump . 15
5.5.3 Non-submerged pump . 15
5.5.4 Expansion vessel . 16
5.5.5 Pump control unit . 16
5.6 System control with monitoring . 16
5.7 Metering . 17
5.8 Distribution . 17
5.9 Risk assessment . 17
6 Sizing . 18
6.1 Storage device . 18
6.1.1 General . 18
6.1.2 Determination of the available volume of rainwater. 19
6.1.3 Determination of the non-potable water demand per day . 20
6.1.4 Calculation methods . 20
6.2 Back-up water supply . 20
7 Installation . 21
8 Differentiation and identification. 21
9 Commissioning . 22
10 Quality of non-potable water . 22
11 Maintenance . 23
Annex A (informative) Examples of calculation methods for storage capacity . 24
A.1 General . 24
A.2 Examples of calculation methods . 24
A.2.1 Basic approach with annual time step . 24
A.2.2 Detailed approach . 25
A.2.2.1 General . 25
A.2.2.2 Input data . 26
A.2.2.3 Simulation principle . 26
A.2.2.4 Application of results . 27
Annex B (informative) Examples of rainwater harvesting systems with different back-up
supply arrangements . 29
Annex C (informative) Example for a commissioning sheet and logbook . 32
C.1 Commissioning sheet . 32
C.2 Logbook . 33
Annex D (informative) Inspection and maintenance . 34
Bibliography . 35

European foreword
This document (EN 16941-1:2018) has been prepared by Technical Committee CEN/TC 165
“Wastewater engineering”, the secretariat of which is held by DIN.
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 July 2018 and conflicting national standards shall be
withdrawn at the latest by July 2018.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent
rights.
EN 16941, On-site non-potable water systems consists of the following parts:
— Part 1: Systems for the use of rainwater
— Part 2: Systems for the use of greywater (in preparation)
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.

Introduction
Ecological and sustainable water management is a goal of rainwater management. Herein rainwater
harvesting and infiltration, as well as the decentralized detention of rainwater, are alternatives to the
customary drainage of rainwater. Rainwater harvesting also reduces the potable water demand and the
discharge of water.
In order to keep the natural cycle of water, excess water from the rainwater harvesting system can be
infiltrated or otherwise evacuated in line with national or regional requirements.
On-site collection and use of rainwater covers a variety of applications like toilet flushing, laundry,
irrigation, climate control of buildings, cleaning, etc. at private and rented properties, residential areas,
community developments, industrial sites, hotels, streets, parks, golf courses, theme parks, car parks,
stadia, etc.
A generic flow chart of rainwater use on-site is presented in Figure 1.

Figure 1 — Generic flow chart of rainwater use
1 Scope
This European Standard specifies the requirements and gives recommendations for the design, sizing,
installation, identification, commissioning and maintenance of rainwater harvesting systems for the use
of rainwater on-site as non-potable water. This European Standard also specifies the minimum
requirements for these systems.
Excluded from the scope of this European Standard are:
— the use as drinking water and for food preparation;
— the use for personal hygiene purposes;
— decentralized attenuation;
— infiltration.
NOTE Conformity with the standard does not exempt from compliance with the obligations arising from local
or national regulations.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
EN 476, General requirements for components used in drains and sewers
EN 805, Water supply - Requirements for systems and components outside buildings
EN 806-2, Specification for installations inside buildings conveying water for human consumption - Part 2:
Design
EN 806-3, Specifications for installations inside buildings conveying water for human consumption - Part
3: Pipe sizing - Simplified method
EN 809, Pumps and pump units for liquids - Common safety requirements
EN 1295-1, Structural design of buried pipelines under various conditions of loading - Part 1: General
requirements
EN 1610, Construction and testing of drains and sewers
EN 1717, Protection against pollution of potable water in water installations and general requirements of
devices to prevent pollution by backflow
EN 12050 (all parts), Wastewater lifting plants for buildings and sites
EN 12056-1, Gravity drainage systems inside buildings - Part 1: General and performance requirements
EN 12056-3, Gravity drainage systems inside buildings - Part 3: Roof drainage, layout and calculation
EN 12056-4, Gravity drainage systems inside buildings - Part 4: Wastewater lifting plants - Layout and
calculation
EN 12056-5, Gravity drainage systems inside buildings - Part 5: Installation and testing, instructions for
operation, maintenance and use
EN 12566-3, Small wastewater treatment systems for up to 50 PT - Part 3: Packaged and/or site
assembled domestic wastewater treatment plants
EN 13076, Devices to prevent pollution by backflow of potable water - Unrestricted air gap-Family A -
Type A
EN 13077, Devices to prevent pollution by backflow of potable water - Air gap with non-circular overflow
(unrestricted) - Family A - Type B
EN 13564 (all parts), Anti-flooding devices for buildings
EN 16323:2014, Glossary of wastewater engineering terms
EN 60335-2-41, Household and similar electrical appliances - Safety - Part 2-41: Particular requirements
for pumps (IEC 60335-2-41)
EN ISO 4064 (all parts), Water meters for cold potable water and hot water (ISO 4064)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 16323:2014 and the following
apply.
3.1
rainwater
water arising from atmospheric precipitation
[SOURCE: EN 16323:2014, 2.1.1.1, modified]
3.2
rainwater harvesting
collecting rainwater from surfaces in order to be used
3.3
rainwater harvesting system
system for collecting rainwater from surfaces in order to be used, which consists of collection,
treatment, storage and distribution elements
3.4
storage device
unit for the storage of harvested rainwater
3.5
cistern
fixed container for holding water at atmospheric pressure for use as part of the plumbing system
3.6
non-potable water
water which has been made available for use, except for drinking, food preparation and personal
hygiene
3.7
non-return valve
device that prevents backflow of water
[SOURCE: EN 16323:2014, 2.2.5.12, modified: "wastewater" was changed to "water"]
3.8
volume of useable water
maximum volume of water that can be extracted from a storage device in normal use which is usually
from the overflow to the lowest extraction point
4 Functional elements of rainwater harvesting systems
Any rainwater harvesting system is described through four main functional elements:
— collection;
— treatment;
— storage; and
— distribution.
Rainwater harvesting systems shall be designed, installed, marked, operated and maintained in such a
way that the required level of safety is ensured at any time and that the required servicing work can be
easily carried out.
Rainwater harvesting systems shall not cause flooding and therefore shall include potential bypasses
and/or properly dimensioned overflows.
5 Design
5.1 Collection
5.1.1 General
The purpose of collection is to harvest rainwater and transport it to a storage device.
The following factors should be taken into account, as these can affect the quality and/or quantity of the
collected water:
— the local rainfall pattern;
— the size of the collection surface;
— the surface’s materials and their drainage characteristics;
— sizing and material of piping systems;
— the levels of pollution of the collection surface;
— the risk of contaminating the system.
5.1.2 Collection surfaces
5.1.2.1 Qualitative aspects
The characteristics of the collection surface (e.g. roofs and paved areas) shall be taken into
consideration depending on the intended use of the rainwater. Pollutants from other sources, e.g. traffic,
industry and animals have to be taken into account.
Common roof materials, e.g. glazed tiles and slate, do not cause any negative effect on the quality of
harvested rainwater.
Other roof collection surfaces may have potential to negatively affect the quality of the water harvested
(see examples in Table 1).
Table 1 — Examples of potential effects of collection surface on the quality of harvested
rainwater
Collection surface Potential effect
Green roof colouration
Bitumen containing material colouration
Cement with fibres emission of fibres in the long term
Copper, lead or zinc roofs increased concentrations of heavy metals
Weathered rough surfaces wash out of solids
Where paved areas or roof areas allowing human amenity are used for collection possible pollutants
due to the use of these areas shall be taken into account.
5.1.2.2 Quantitative aspects
Collection surfaces made of different materials have different characteristics regarding the drainage of
rainwater. The volume of the harvested rainwater is influenced by the surface yield coefficient (e).
Unless otherwise specified, typical values are given for different materials in 6.1.2, Table 2.
NOTE The surface yield coefficient differs from the run-off coefficient as specified in EN 12056-3, where it is
used for the hydraulic design of pipes. The surface yield coefficient aims to determine the average yield.
5.1.3 Collection piping system
Collection piping systems should allow the rainwater to flow from the collection surface to the storage
device by gravity or siphonic action. Access for inspection, maintenance and cleaning has to be planned
and installed.
Collection pipework from the roof within the rainwater harvesting system should not discharge into
open gullies because additional contamination could occur.
The non-pressure pipes and fittings shall meet the general requirements according to EN 476 and the
relevant product standards. The dimensioning shall be done in accordance with EN 12056-1 and
EN 12056-3. Underground rainwater pipes shall be designed according to EN 1295-1 and installed
according to EN 1610.
5.2 Treatment
5.2.1 General
The main purpose of treatment is to ensure a specific water quality depending on the intended use.
Additional purposes are the protection of the system components and the reduction of maintenance.
Treatment may involve biological, chemical or physical processes or a combination of them. Treatment
shall be done upstream within and potentially downstream of the storage device.
Treatment covers several operations:
— removal of coarse particles upstream of the storage (see 5.2.2);
— retention of fine particles by sedimentation and flotation in the storage device (see 5.3);
— filtering downstream of the storage device, depending on the intended use.
Disinfection, deodorization and/or discoloration may be required additionally (see 5.2.3).
A rainwater harvesting system shall provide water suitable for flushing toilets, laundry and garden
watering in most residential, industrial and commercial situations without the necessity of additional
treatment (see 5.2.3) unless identified by risk assessment referred to in 5.9.
The treatment system shall:
— be water resistant and durable;
— be accessible for maintenance (see Clause 11);
— not affect the hydraulic operation of the overall drainage system;
— withstand the maximum stresses and loads exerted during its handling, installation, use and
maintenance; and
— have a hydraulic efficiency ratio of at least 90 %.
The flow section of the overflow of the treatment device shall be designed for the discharge of
maximum flow.
5.2.2 Preliminary treatment
Preliminary treatment (e. g. filters, separators) shall be designed and located upstream of the storage
device and may consist of more than one device. The type and dimensioning of preliminary treatment
shall be selected according to the nature and size of the collection surface.
The purpose of preliminary treatment is to prevent the inflow of most coarse solids and organic matter
into the storage device. The maximum particle size entering the storage device shall be equal or less
than 1 mm for in-house use. If solids are retained, they shall be removed regularly or during a manual
intervention.
5.2.3 Additional treatment
Additional treatment (e. g. filtration, disinfection) of the stored rainwater shall be included if the
intended use demands higher quality.
5.3 Storage
5.3.1 General
The rainwater harvesting system shall, at a minimum, include one storage device which may be
positioned either above or below ground.
The purpose of the storage device is:
— to conserve a suitable volume of rainwater for the intended use and the collection possibilities;
— to treat the incoming water (sedimentation, flotation); and
— to protect the quality of this water from risks of deterioration.
The storage device shall be protected against frost, extreme temperatures and direct sunlight, for
instance buried underground.
The structural behaviour shall be taken into account when positioning the storage device.
5.3.2 Materials
The materials used shall not have a negative effect on the quality of the stored water and the
environment of the installation.
The materials (e. g. concrete, steel, Poly (vinyl chloride) (PVC-U), Polyethylene (PE), Polypropylene
(PP), Glass Reinforced Polyester (GRP-UP)) used for prefabricated factory built storage devices shall
meet the conditions described in EN 12566-3.
The material shall be non-translucent and/or UV stable. Where translucent material is used, light shall
be excluded.
The materials constituting the submerged components shall be corrosion resistant.
5.3.3 Dimensions
When prefabricated components are used, the overall dimensions, access and connection dimensions
and tolerances shall be stated by the manufacturer. Individual storage devices may be connected to
each other.
5.3.4 Capacity
The nominal capacity is the maximum volume of water that can be retained within the storage device
and shall be stated by the manufacturer or designer within ±0,1 m .
The capacity can be determined by testing or calculation.
5.3.5 Structural behaviour
Storage devices shall withstand the maximum stresses and loads exerted during its handling,
installation, use and maintenance. This shall be assessed either by calculation or testing.
Above-ground storage devices shall withstand the action of hydrostatic pressure without generating
excessive deformation adversely affecting its function.
5.3.6 Watertightness
The storage device shall be watertight at the level of:
— the walls constituting it;
— the couplings ensuring the hydraulic connections; and
— the storage device wall penetrations used for the possible passage of electric cables.
5.3.7 Connections and internal pipe system
The nominal diameters of the inlet and outlet fittings of the storage device shall be stated by the
manufacturer.
The inlets, outlets and other connections of the storage device shall be equipped with fittings with
standardized dimensions (i.e. sockets, spigots) equipped with seals and enabling assembly using
standardized pipes.
The inflow pipe of the harvested rainwater is terminated below the minimum water level of the storage
device to prevent the disturbance of any material at surface level. A calming inlet (see Figure 4) shall be
installed to prevent re-suspension of the solids that may have accumulated on the bottom.
Protection against the entry of small animals shall be provided.
5.3.8 Access
The storage device shall be equipped with an access to permit regular inspection and maintenance. The
access shall be secured (e.g. by a cover with a locking feature or sufficient weight).
For the access of a person, the dimensions given in EN 476 shall be considered. When access of a person
is not intended, an opening with a dimension (i.e. width for a square section or diameter for a circular
section) not less than 400 mm minimum shall be used.
Shafts and access covers shall prevent unintentional contamination of the storage device.
5.3.9 Overflow
Storage devices shall be equipped with an overflow to allow excess water to be discharged. Excess
water should be infiltrated or otherwise evacuated into surface water bodies. Discharge into the sewer
system should only occur if inevitable (see EN 12056-3).
Where the overflow is connected to a sewer system, the overflow shall be equipped with an odour trap.
Where the overflow is connected to the sewer system where there is a risk of backflow from the sewer
system, the overflow shall be equipped with an anti-flooding device according to EN 13564 (all parts).
The anti-flooding device shall remain accessible for servicing.
Every overflow shall have provisions to avoid pollution. Any protection provided shall not reduce the
effective cross-sectional area of the overflow. Overflows fitted to above ground storage devices should
be screened.
During overflow a siphonage of the storage device shall be avoided.
The overflow pipe shall be dimensioned to evacuate the possible maximum inflow of the storage device.
5.4 Back-up water supply
5.4.1 General
The rainwater harvesting system shall incorporate a back-up water supply where continuous flow is
needed. The back-up water may be introduced into:
a) a break cistern prior to its pump, for delivery to the distribution pipework, e.g. purpose-designed
module; or
b) an intermediate cistern, usually located at high level, e.g. gravity supply; or
c) the storage device, either directly or by discharging into the collection pipework, but not before
treatment.
NOTE Annex B gives examples of typical systems with different back-up supply arrangements.
In the case of back-up water supply using potable water, the potable water supply system shall be
protected with an appropriate protection unit (see 5.4.2).
The possibility of a flooding of the back-up water supply device (e.g. via reflux) shall be eliminated, e.g.
by installing the back-up water supply device above the backwater level.
When the water level in the storage device is below a given minimum, the back-up water supply control
shall automatically ensure the operational reliability of the system. This can also be achieved by a
control system (see 5.6).
The back-up water supply shall be fitted with a control mechanism which ensures that the amount of
water supplied is minimized to that needed for immediate use. It is recommended that this is provided
from a make-up module or an intermediate cistern.
The design of the system shall ensure that there are no dead legs upstream, e.g. on the potable water
supply and suitable turnover of water is achieved, to avoid water to become stagnant.
In order to prevent wasting potable water, the storage device with valve-controlled water inputs shall
have a warning system so any failure is readily noticeable.
5.4.2 Backflow protection device
To prevent non-potable water entering the potable or public water supply, the back-up water supply
shall be fitted with a protection unit that is capable of providing fluid category 5 (an air gap) in
accordance with EN 1717, such as described:
— in EN 13076, for family A, type A, "AA unrestricted air gap", disconnectors (see Figure 2): An "AA"
air gap is a visible unobstructed and complete air gap placed permanently and vertically between
the lowest point of the inlet feed orifice and any surface of the receiving vessel that determines the
maximum operational level at which the device overflows.

Key
r gap (double the inner diameter of the feed orifice with a
1 feed pipe A
minimum of 20 mm)
2 feed orifice D internal diameter of feed pipe (bore)
3 receiving vessel H maximum water level
4 spillover level
5 maximum angle from the vertical (15°)
Figure 2 — Unrestricted Type AA air gap according to EN 13076
— in EN 13077, for family A type B, "AB air gap with non-circular overflow" disconnectors (see
Figure 3): An "AB" air gap is a permanent and vertical distance between the lowest point of the feed
orifice and the critical water level. The overflow shall be of non-circular design and shall be able to
evacuate the maximum flow of water in the event of overpressure.
Key
1 feed pipe 6 upstream face of the overflow arrangement Uw (Uw ≥ 5 h)
2 feed orifice 7 critical water level
3 receiving vessel A air gap
4 spillover level D internal diameter of feed pipe (bore)
5 optional warning pipe H maximum water level
h distance between overflow and critical water level
Figure 3 — Unrestricted Type AB air gap with non-circular overflow according to EN 13077
Flow rates, head loss and installation requirements shall be taken into account when selecting the
backflow prevention device.
Where the backflow prevention device is to provide water to the storage device directly and there is a
risk of odours venting back into the building, an odour trap shall be installed.
5.5 Pumping
5.5.1 General
For systems, other than those which distribute the collected rainwater by gravity, one or more pumps
shall be used to ensure its continual availability.
NOTE 1 The operational safety and hydraulic demand will dictate whether a single pump or multiple-pump
system is needed.
The flow rate and the required pressure head of the pump shall be determined in accordance with
EN 12056-4, EN 12050, EN 806-2 and/or EN 806-3, as applicable.
The pump shall be selected and arranged such that:
— energy use and noise are minimized;
— air is not introduced into the suction lines;
— it is protected against freezing; and
— it is provided with isolation valves for maintenance and repair.
The pump shall be equipped with dry-run protection, which may be part of the pump or provided by an
external control device (see 5.6).
Surges, water hammer and hunting from the pump shall be absorbed and prevented from causing
undue high pressures, e.g. by the incorporation of expansion vessels or pressure controls, in order to
prevent bursting and excessive draw off.
The pump shall comply with either EN 60335-2-41 for a domestic installation or EN 809 for other types
of installations.
Multiple-pump systems shall conform to EN 12056-4 or EN 12050 with a standby pump if necessary.
NOTE 2 Several pumps can operate alternately to equalize their operating time.
The pump shall ensure the distribution of water under the conditions stated in 5.8 of this standard.
A non-return valve shall be provided to prevent back-flow.
5.5.2 Submerged pump
Where a submerged pump is used, it shall comply with the following:
— a minimum water level shall be maintained above the suction point to ensure that neither air,
sediment nor floating debris are sucked in;
— the pump shall be installed in a way to prevent it from unintended movement, e. g. keeping the
suction line in the correct positioning;
— a non-return valve shall be installed in the pipe in order to keep the pipe primed; and
— it shall be possible to remove and replace the pump without needing special tools or to enter the
tank, e.g. for maintenance.
5.5.3 Non-submerged pump
Where a non-submersible pump is used, it shall comply with the following:
— the suction lines shall be airtight;
— the suction lines shall be installed in a way to minimize hydraulic friction loss;
— the suction lines shall be laid in a steady gradient towards the pump;
— a non-return valve shall be installed in the pipe in order to keep the suction pipe primed; and
— the water intake shall be constructed so as to avoid suction of the supernatant layer, sediments or
air.
Self-priming pumps are recommended, because of ease of operation (e. g. easy commissioning,
overcoming of potential air bubbles in suction lines).
An example for a floating suction device on a non-submerged pump is shown in Figure 4.
Key
1 indicator/sensor
2 overflow with odour trap
3 floating suction device
4 calming inlet
5 minimum water level
6 maximum water level
Figure 4 — Example of a floating suction device on a non-submerged pump
The pump shall be placed in a well-ventilated location with sound and vibration free mountings.
5.5.4 Expansion vessel
An expansion vessel may be required to prevent the pump from starting too frequently if the system has
a risk of low extraction or leaks.
The expansion vessel shall be sized according to the type of controls used (e. g. fixed or variable speed)
and installed in a manner which prevents any deterioration of water quality within the vessel, e.g. in the
vertical orientation.
NOTE Using an expansion vessel may allow the pump to be used less and therefore improve the energy
balance.
5.5.5 Pump control unit
Pumps shall be equipped with a pump control unit to automatically control the pumps with a manual
override. The control shall permit manual operation.
The pump control unit shall:
— control pumps and minimize operational wear and energy use; and
— protect the pumps from running dry.
5.6 System control with monitoring
A control and monitoring system should be incorporated in the rainwater system to ensure, as a
minimum, that users are aware of whether the system is operating effectively.
The system control shall inform the user of:
— the status of water supply (non-potable water or back-up water); and
— any malfunctions, e. g. pump failure, back-up supply failure.
Other monitoring may also be included, e. g. water metering, water level, the overflow, tank
temperature and other parameters.
The control unit should permit manual override. Data may be monitored and stored.
The system control may be linked to a building management system.
5.7 Metering
Water meters may be used to control the rainwater harvesting system.
When meters are required to quantify the volumes of non-potable water used inside the building and
discharged into the public sewer system, reference shall be made to the specifications of EN ISO 4064-1
to EN ISO 4064-5.
5.8 Distribution
The purpose of distribution is to feed the points of use with non-potable water and the possibility of
back-up water supply. The distribution performed shall ensure the integrity and protection of public
and private potable water distribution systems.
The treated rainwater/non-potable water shall be distributed by:
a) pumping it from the storage device directly to the point of use; or
b) pumping it from the storage device to an intermediate cistern/tank near the point of use; or
c) using a gravity cistern; or
d) using a full gravity system.
Cross-connection of non-potable water distribution pipes with other piping systems shall not occur.
Domestic type water distribution systems (e.g. for toilet flushing) used for the distribution of non-
potable water shall be designed according to the applicable European Standards (e. g. EN 805, EN 806).
For the identification of pipes for conveying rainwater, see Clause 8 and the relevant product standards.
Rainwater, non-potable water and drinking water usually have different chemical characteristics (pH
for instance). The materials constituting the pressure pipe shall be chosen considering the risk of
corrosion.
5.9 Risk assessment
Risk assessment shall be carried out to determine whether the system is safe and fit for purpose. This
should take place when the system is being designed.
The risk assessment shall consider the effects of exposure to, and the potential impacts of, the system
on people, the environment, and physical assets.
The risk assessment shall consider the design, installation, testing and commissioning, operation and
maintenance of the system, including water quality, structural stability, electrical safety and access
provision.
6 Sizing
6.1 Storage device
6.1.1 General
The sizing of the volume of the rainwater storage device results from an analysis of the relationship
between the rainwater that can be harvested and the demand of the non-potable water for the intended
use requirements.
The following factors shall be considered in order to be able to calculate the size of the storage device:
— the rainfall data (amount, intensity, pattern of rainfall, dry periods);
— the size and type of the collection surface;
— the number and type of intended applications, both present and future; and
— the hydraulic efficiency of equipment used (e.g. filters).
Other factors may influence the choice of the size of the storage device (e.g. available area, groundwater
level).
The nominal capacity as shown in Figure 5 consists of:
— the volume of useable rainwater; and
— the volume of non-useable rainwater.

Key
1 volume of non-usable rainwater
2 volume of nominal capacity
3 volume of usable capacity
4 maximum water level
Figure 5 — Capacities of storage device
The storage device capacity of the rainwater harvesting system can be determined using one of the
methods described in the Annex A.
The storage devices should be selected on the basis of useable volume, rather than the total capacity of
the storage device.
6.1.2 Determination of the available volume of rainwater
The available volume of rainwater (Y ) that can potentially be harvested for a time step (t) from
R
different areas (index ) defined using the following formula:
i
(1)
Y =∑Ah× ××e η
R i ii i
where
Y is the rainwater yield per time step t, expressed in litres (l);
R
A is the horizontal projection of the collection area, expressed in square metres (m ) (see a);
h is the total rainfall for a chosen time step t, expressed in millimetres (mm) (see b);
e is the surface yield coefficient (see c);
η is the hydraulic treatment efficiency coefficient (see d).
a) collectio
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