Frequently Asked Questions & Answers
Halsted Rain is a leading supplier of Urban Rainwater Harvesting systems used for toilet flushing,
laundry and garden irrigation. We have specialist knowledge and experience of UK market
requirements for aboveground and shallow below ground rainwater harvesting systems and strong
collaborative relationships with other leading manufacturers of rainwater products worldwide.
Below are the most frequently asked questions regarding rainwater harvesting and Halsted Rain has
provided the following guidance to assist specifiers evaluate our systems.
What is Urban Rainwater Harvesting?
Urban rainwater harvesting is the installation of purpose designed aboveground slim line and
belowground Flatform ‘shallow dig’ tank systems to collect and use rainwater in domestic and light
commercial buildings for toilet flushing, clothes washing and garden irrigation. This approach is widely
used throughout the developed world as a means of reducing the use of mains water. Typically a third
of mains water used in a domestic house is for toilet flushing and this rises to 85% in many
commercial premises. The simplicity and affordability of this technology make it very suitable for
What are the main components of an Urban System?
Rain is collected from a down pipe by an efficient filter diverter and stored in a slim line or Flatform
tank system before being pumped on demand to the connected services. In the event that there is
insufficient rainwater to meet demand, a mains top up unit adds a small amount of mains water to the
system to maintain services.
What are the benefits of a Urban Rainwater Harvesting System?
Urban rainwater harvesting systems offer the durability, utility and permanence of a traditional
cylindrical below ground system and are easier to install and maintain. They are an ideal retrofit
solution that avoids the costly civil work and disruption required when installing traditional below
ground systems. Urban modular tank systems make it simple to add units to provide the required
capacity and modules can always be added at a later stage if water needs change.
What size of system do I require?
This depends on the size of the roof catchment, annual rainfall, space available for water storage and
the expected usage. A system should be matched to the property and usage. The temptation to
oversize a system should be resisted to ensure water quality is maintained and to avoid unnecessary
Is the quality of rainwater collected from a roof and stored in an aboveground tank suitable for use in a home or business premises for toilet flushing?
Modern systems have been designed with exactly this application in mind. Extensive scientific
research by universities, relief aid agencies and industry has shown that a properly installed
aboveground or belowground system to supply rainwater for toilet flushing presents no increased risk
to public health. In the UK collected rainwater is not approved for human consumption. Halsted Rain
advises the following when installing an urban harvesting system to maintain a healthy rainwater
- Ensure the gutter line is in good repair to avoid the collection of debris and the pooling of
rainwater between storms.
- Use a quality filter and diverter to remove leaf litter and debris that descends from the roof
and fit a feature to prevent back flow of foul water from the drain.
- Install a quality opaque aboveground tank on a north or west facing wall or shade or screen
the tank from the mid-day sun. Install in a location with good ventilation.
- Size the system so that the water is being regularly used and the tank overflows regularly
throughout the year to the main drain which removes any fine particles of floating organic
The water in a well designed and maintained rainwater harvesting system is generally clean for
purpose before it enters storage and the system should be used regularly to prevent the water quality
Is freezing of aboveground systems during periods of cold weather going to interrupt the supply of
rainwater to the toilet cistern?
Experience shows that in a temperate climate such as the UK it is unlikely that a purpose designed
aboveground rainwater harvesting system will freeze. During periods of cold weather micro climatic
effects moderate the temperature close to buildings by several degrees and the storage tanks are
insulated by a thick HDPE wall relative to the size of tank. In winter, the tanks are usually full of
naturally circulating water and a prolonged period of severe cold would be required to freeze this
mass of water. Halsted Rain advises the following to mitigate the risk of any interruption to supply due
to freezing weather.
- Locate storage tanks against a sheltered wall to gain maximum benefit from the ‘urban heat
- Install the pump package and mains top up valve inside the building, a protective enclosure or
submerged inside larger tanks to prevent any frost damage.
- Insulate the tank outlet fitting and exposed pipe to the pump and services with external quality
mineral wool mat, insulating tape or moulded insulation foam.
In less temperate climates such as Canada, for example, or very exposed sites, additional measures
can be taken to winterise aboveground tanks such as the use of thermostatically controlled trace heat
products and thermal blankets.
Is planning consent required for the installation of an Urban Rainwater Harvesting System?
Councils give expeditious and sympathetic handling of planning permission to applications for new
build and extensions which include rainwater harvesting. The retrofitting of most systems do not need
planning consent, but exceptions apply for Listed Buildings, buildings in Conservation Areas and
World Heritage sites. If you are in any doubt about planning requirements contact the local planning
Is Urban Rainwater Harvesting covered by Building Regulations?
There are currently no direct building regulations for rainwater harvesting. However, Hygiene and
Drainage are covered by the Building Regulations and can influence rainwater harvesting system
Several other associated regulations apply; In England and Wales the Water Supply Regulations
1999 (Water by-laws 2000 in Scotland and Water Supply (Water Quality) Regulations (Northern
Ireland) 2002 must be adhered to. These regulations are enforced by the water supplier.
The essential requirements of the regulations specific to rainwater harvesting are;
- No cross bonding of rainwater piping with potable supply pipes
- Prevention of backflow to potable water supplies according to CEN EN1717 with air gaps
- The clear marking of rainwater pipes according to WRAS # 9-02-05
- Material specifications, where contact with wholesome water is permissible meet the prevailing
For further guidance on the design of rainwater harvesting systems contact Halsted Rain.
In addition to Urban Rainwater Harvesting, Halsted Rain offers a range of other water management
and treatment technologies for greywater and wastewater, some of which can be integrated in to
sustainable drainage solutions.