General flood information
Stormwater management
Stormwater is water that originates during precipitation events. It may
also be used to apply to water that originates with snowmelt that enters
the stormwater system. Stormwater that does not soak into the ground becomes
surface runoff, which either flows directly into surface waterways or
is channeled into storm sewers, which eventually discharge to surface
waters.
Stormwater is of concern for two main issues: one related to the volume
and timing of runoff water (flood control and water supplies) and the
other related to potential contaminants that the water is carrying, i.e.
water pollution.
Stormwater is also a resource and ever growing in importance as the world's
human population demand exceeds the availability of readily available
water.
Techniques of stormwater harvesting with point source water management
and purification that can potentially make urban eManaging the quantity
and quality of stormwater is termed, "Stormwater Management."[5]
The term Best Management Practice (BMP) is often used to refer to both
structural or engineered control devices and systems (e.g. retention ponds)
to treat polluted stormwater, as well as operational or procedural practices.
There are many forms of stormwater management and BMPs, including:
• manage stormwater to control flooding and erosion;
• manage and control hazardous materials to prevent release of pollutants
into the environment (source control);
• plan and construct stormwater systems so contaminants are removed
before they pollute surface waters or groundwater resources;
• acquire and protect natural waterways where they still exist or
can be rehabilitated;
• build "soft" structures such as ponds, swales or wetlands
to work with existing or "hard" drainage structures, such as
pipes and concrete channels;
• revise current stormwater regulations to address comprehensive
stormwater needs;
• enhance and enforce existing ordinances to make sure property
owners consider the effects of stormwater before, during and after development
of their land;
• educate a community about how its actions affect water quality,
and about what it can do to improve water quality; and
• plan carefully to create solutions before problems become too
great. Environments self sustaining in terms of water.
Integrated water management (IWM) of stormwater has the potential to
address many of the issues affecting the health of waterways and water
supply challenges facing the modern urban city.
Also known as low impact development in the United States, or Water Sensitive
Urban Design (WSUD)[6] in Australia, IWM has the potential to improve
runoff quality, reduce the risk and impact of flooding and deliver an
additional water resource to augment potable supply.
The development of the modern city often results in increased demands
for water supply due to population growth, while at the same time altered
runoff predicted by climate change has the potential to increase the volume
of stormwater that can contribute to drainage and flooding problems. IWM
offers several techniques including stormwater harvest (to reduce the
amount of water that can cause flooding), infiltration (to restore the
natural recharge of groundwater), biofiltration or bioretention (e.g.,
rain gardens) to store and treat runoff and release it at a controlled
rate to reduce impact on streams and wetland treatments (to store and
control runoff rates and provide habitat in urban areas).
There are many ways of achieving low impact development (LID). The most
popular is to incorporate land-based solutions to handle stormwater runoff
through the use of retention ponds, bioswales, infiltration trenches,
sustainable pavements (such as pervious concrete), and others noted above.
LID can also be achieved by utilizing engineered, manufactured products
to achieve similar, or potentially better, results as land-based systems
(underground storage tanks, stormwater treatment systems, biofilters,
etc.). The proper LID solution is one that balances the desired results
(controlling runoff and pollution) with the associated costs (loss of
usable land for land-based systems versus capital cost of manufactured
solution). Green (vegetated) roofs are also another low cost solution.
IWM as a movement can be regarded as being in its infancy and brings together
elements of drainage science, ecology and a realization that traditional
drainage solutions transfer problems further downstream to the detriment
of our environment and precious water resources.
Flood water management
A flood is an overflow of an expanse of water that submerges land.[1]
The EU Floods directive defines a flood as a temporary covering by water
of land not normally covered by water.[2] In the sense of "flowing
water", the word may also be applied to the inflow of the tide. Flooding
may result from the volume of water within a body of water, such as a
river or lake, which overflows or breaks levees, with the result that
some of the water escapes its usual boundaries.[3]
While the size of a lake or other body of water will vary with seasonal
changes in precipitation and snow melt, it is not a significant flood
unless such escapes of water endanger land areas used by man like a village,
city or other inhabited area.
Floods can also occur in rivers, when flow exceeds the capacity of the
river channel, particularly at bends or meanders. Floods often cause damage
to homes and businesses if they are placed in natural flood plains of
rivers. While flood damage can be virtually eliminated by moving away
from rivers and other bodies of water, since time out of mind, people
have lived and worked by the water to seek sustenance and capitalize on
the gains of cheap and easy travel and commerce by being near water. That
humans continue to inhabit areas threatened by flood damage is evidence
that the perceived value of living near the water exceeds the cost of
repeated periodic flooding.
The word "flood" comes from the Old English flod, a word common
to Germanic languages (compare German Flut, Dutch vloed from the same
root as is seen in flow, float; also compare with Latin fluctus, flumen).
Deluge myths are mythical stories of a great flood sent by a deity or
deities to destroy civilization as an act of divine retribution, and are
featured in the mythology of many cultures.
Rainwater Harvesting
Rainwater harvesting is the accumulating and storing, of rainwater for
reuse, before it reaches the aquifer. It has been used to provide drinking
water, water for livestock, water for irrigation, as well as other typical
uses given to water. Rainwater collected from the roofs of houses, tents
and local institutions, can make an important contribution to the availability
of drinking water.It can supplement the sub soil water level and decrease
urban greenery. Water collected from the ground, sometimes from areas
which are especially prepared for this purpose, is called Stormwater harvesting.
In some cases, rainwater may be the only available, or economical, water
source. Rainwater harvesting systems can be simple to construct from inexpensive
local materials, and are potentially successful in most habitable locations.
Roof rainwater can't be of good quality and may require treatment before
consumption. As rainwater rushes from your roof it may carry pollutants
in it such as the tiniest bit of mercury from coal burning buildings to
bird feces. Although some rooftop materials may produce rainwater that
is harmful to human health, it can be useful in flushing toilets, washing
clothes, watering the garden and washing cars; these uses alone halve
the amount of water used by a typical home. Household rainfall catchment
systems are appropriate in areas with an average rainfall greater than
200 mm (7.9 in) per year, and no other accessible water sources (Skinner
and Cotton, 1992). Overflow from rainwater harvesting tank systems can
be used to refill aquifers in a process called groundwater recharge, though
this is a related process, it must not be confused with Rainwater harvesting.
There are a number of types of systems to harvest rainwater ranging from
very simple to the complex industrial systems. The rate at which water
can be collected from either system is dependent on the plan area of the
system, its efficiency, and the intensity of rainfall (i.e. annual precipitation
(mm per annum) x square meter of catchment area = litres per annum yield)
... a 200 square meter roof catchment catching 1,000mm PA yields 200 kLPA.
Rainwater harvesting can (a) assure an independent water supply during
water restrictions, that is though somewhat dependent on end use and maintenance,
(b)usually of acceptable quality for household needs and (c) renewable
at acceptable volumes despite forecast climate change (CSIRO, 2003). It
produces beneficial externalities by reducing peak storm water runoff
and processing costs. In municipalities with combined sewer systems, reducing
storm runoff is especially important, because excess runoff during heavy
storms leads to the discharge of raw sewage from outfalls when treatment
plant capacity cannot handle the combined flow. RH systems are simple
to install and operate. Running costs are negligible, and they provide
water at the point of consumption. (d) Rainwater harvesting in urban communities
has been made possible Tanks such as this provide an attractive yet effective
solution to rainwater catchment.
BS8515:2009
FAQ
What is Rainwater Harvesting?
Rainwater harvesting is a way of saving the rainwater which would normally flow off a roof and down the drain, and using it as piped water to flush toilets and for the garden watering, yard washdown, vehicle and car washing, and even for your washing machine, instead of using expensive treated drinking (potable) water.
Are there planning regulations associated with rainwater Harvesting?
They are not required directly by Building Regulations, although they may be linked with the Planning Permission for the storm-water management of the site. Building Regulations do cover the installation itself, tank siting & pipe runs etc.
Will a system affect my homes eco rating?
Yes, rainwater harvesting is an important ER criterion. The EcoHomes rating system addresses all aspects of reducing potable water demand in a dwelling. Installing a rainwater harvesting system adds to the credit rating for water use.
What types of rainwater harvesting systems are there?
Un pressurised: rainwater is gravity fed from a header tank, usually
in the loft to the point of use.
Pressurised: The rainwater is pumped directly from the above or under-ground
tank to the required point of supply. i.e. toilet, outside tap etc.
Is there a danger of legionella?
No, the system does not provide the conditions necessary for the cultivation of Legionella. With the water stored underground it is dark cool and is kept well oxygenated. Legionella cannot cultivate in these conditions.
How is the system maintained?
As a general rule filters should be thoroughly cleaned once a year and we recommend a full 'flushing' of the system every three years. A treatment with an anti-algicide such as sprayguard is also recommended. A correctly designed harvesting system overflows on a regular basis to remove floating matter and the pumps are very reliable. Maintenance should only be carried out by qualified or experiences personnel. Combined harvesters have their own teams available year round to keep systems working efficiently.
What kind of pumps are used in the systems?
Pumps can be housed either internally in the tank or mounted within a control unit fitted in a garage, plant room etc. Pumps should have run dry protection and should have a pressure switch fitted to stop hunting. Internal tank pumps need to be constantly submersed in water to prevent damage from the air, from debris or sediment that may be sucked in. An external pump or control unit should have an audible alarm to identify faults in the system, when fresh water is being used etc.
How much does it cost to run a rainwater harvesting pump?
It typically takes 1.5- 2.0 kWh to pump 1 cubic meter of water (1000 litres). For a typical house using rainwater for WCs, washing machine and the garden, pumping costs are between 5-10p per week
Do I need to have a water meter?
This is not generally necessary; however the absence of one will reduce you seeing the benefits of harvesting rainwater immediately.
What does the British Standard BS8515:2009 cover?
BS8515 covers the design, installation, water quality, risk management and maintenance of rainwater harvesting systems. This applies to both new and retrofit properties.
What is the payback period?
This figure will depend upon the rainwater that you collect and the use. A typical domestic client will see a payback between 5-10 years. Commercial clients should be able to reduce this figure to 2-5 years.
Is it only for new builds?
No systems can easily be retro-fitted.
What design aspects are to be considered to comply with BS8515?
Designs should be provided by an industry expert, amount and intensity of rainfall, type of intended applications both now and in the future will be considered. Tank size will depend upon ground conditions and surface water. All these as well as filtration requirements, end use by clients, site restrictions and other factors not necessarily covered by BS8515 will be considered when designing a system.
What happens when there is no rain?
In the absence of rain, correctly designed systems will have a 'mains top up' facility ( not always required for garden systems ). This will fill the tank with the minimum required amount of water to keep it functioning until the rain returns or a small holding tank on the management unit..
Is rainwater harvesting suitable for work as well as at home?
Yes, in schools, hospitals, offices, commercial premises, rainwater can typically be used for toilets, vehicle washing, yard wash down and watering plant pots/gardens.
Can it be used when there is a hosepipe ban?
It is possible to use a hosepipe connected to a rainwater tank, provided
that the tank is not connected to a mains water supply. Many people are
doing this already by using a water butt.
Is it only for houses?
No, bungalows and commercial premises are also very suitable, the only limitation is the area of the roof to capture rain, in fact commercial and industrial buildings can make the largest savings.
Where is it installed?
The tank should be buried under a car or vehicle park, landscaped area,
garden, patio or drive, with space left for the round access cover. Most
systems are designed so that they can accept cars driving over them if
suitably installed. Or an above ground system can be installed next to
the house or property.
Are there any grants available?
Not for domestic installations yet, although several organisations are petitioning the government for assistance. For commercial installations, there is a tax relief scheme (ECA) for suitable approved equipment on the Water Technology List.
How clean is the water?
The rainwater is filtered as it enters the storage tank, to remove particles and other matter. It is kept in the dark and kept oxygenated to discourage algal growth, and properly designed systems are designed with calming inlets, which ensure that any sediment at the bottom of the tank does not get stirred up. The water is not drinking water fit for humans.
How do you stop debris from entering the system?
A filter is fitted along with a ‘calming inlet’. The filter has to meet strict criteria covering its weather resistancy, accessibility and efficiency.
How much rainwater does a system collect?
This depends on the area and angle of your roof, and your rainfall. Averages of 100,000 litres per household are commonly quoted, much more for large roofed commercial buildings.
Is the tank covered by BS8515:2009?
Yes, all tanks are covered. They need to be water tight, discourage microbial
growth, avoid stagnation and thereby legionella .Tanks need to be suitably
load bearing and need to resist floatation.
Pipes to and from the tank need to be clearly marked, rainwater pipes
can be green or black (not blue) .Special marker tape can be purchased
to show piping on a scan.
Does the tank need an overflow?
Yes, the overflow needs to be the same diameter or even larger than the inlet, it must also be fitted with back flow prevention. Overflows are important as a tank should be the correct size so as to overflow at least twice a year to ‘flush the system’.
How much would this save on water bills?
Depending on your normal usage, it can save 45 to 50% for the domestic user and 80% for the commercial user of the treated drinking water from the mains. Having metered water is the best way of appreciating the difference.
So, why should people buy Rainwater Harvesting systems?
To save on water bills and show an appreciation for this increasingly precious resource whilst making a difference to our environment.
How does rainwater harvesting work?
A storage tank is fitted to your storm water drain from your roof, and falling rain enters the tank through a filter which removes leaves and other matter. The storage tank is usually buried under car or vehicle parks, a garden or under the entrance access or drive, and contains a pump which pumps the rainwater to the building where it is piped to the toilets, and to the outside taps. Above ground tanks are also available.
How much water can a system save?
Depending on your normal usage, it can save 30 to 50% of the treated drinking
water from the mains in houses and up to and up to 80% of the treated
drinking water in a business or commercial building.
What can you use the water for?
Filtered, untreated rainwater should only be used for non- drinking or bathing purposes: toilet flushing, gardens and vehicle or yard wash downs.
How much does it cost?
Domestic systems can cost from about £2500 up to £4000 plus including installation costs, depending on size of tank. Commercial systems can cost a lot more depending on size and requirement, but usually have a much quicker 'pay back' period due to the size of roof and high usage.
Could rainwater get into my drinking supply?
Not in a properly designed system, the pipe work is entirely separate and should be identified as non-potable. BS8515:2009 stipulates that backflow prevention should be fitted upstream of or at a point where any two systems meet. This form of back flow prevention must be of type AA or AB Air gap conforming to BS13076 and BS EN13077.
Do I need a big roof area to make it worthwhile?
No, most domestic roofs are more than adequate, but the bigger and flatter the roof area, the more rain will be captured, and the more the rainwater will substitute for treated mains water.
Is Rainwater Harvesting a new idea?
No, collection re-use of rainwater from roofs can be traced back thousands of years in hot, dry countries around theMediterranean. In continental Europe, some 100,000 are installed annually; Germany has been using and refining the technology since the early 80s.
Can a roof affect the efficiency of a system?
Yes, all these need to be free-draining and suitable to stop debris from entering the system. Other roofs such as green roofs etc absorb water and results in less run off and more colouration.
This guide has been produced to assist professionals who are interested in the specifications of rainwater harvesting systems. Enabling them to make an informed choice of supplier based on the criteria set down in BS8515:2009. At Combined Harvesters Ltd we are committed to a long term approach to the supply of all rainwater harvesting and stormwater management products, ensuring quality throughout the chain.
Save your water…save your money…save your environment.
Can I use rainwater for my garden?
Absolutely, in fact the water is a better quality with less harmfull chemicals.
Here at Storm attenuation, we both design, stock, install and most important
of all, manufacture. You can sit back and be assured that you are getting
the very best of British manufacturing.When deciding which systems and
or supplier to chose, ask yourselves a few very important questions:
Is Uk manufactured important?
Apart from the fact that you are buying products that have been specifically
designed for the UK market and UK fittings, you are not adding to the
carbon footprint of an expensively imported tank. Usually hauled overland
from Germany.
Are one piece tanks inmportant?
That is only a question you can answer yourself, Are you comfortable burying
an expensive tank in the ground that is clipped together and relies on
being watertight on a rubber seal that the fitters may or may not get
right?
Do I need to consider concrete backfill?
Absolutely, when you consider that if you do need to backfill your tank
installation with concrete (as is the case with most GRP tanks)then the
amount of concrete for an average tank can be as much as 18 cubic metres
@£90 per cube , this can easily double your installation cost
What about filtration, do I need to worry about Legionella?
Not with tanks underground, however we do have a Raincatcher filter that
has varying degrees of filtration from 50 to 300 microns. Legionalla and
other bacterial issues come to the fore with rainwater stored above ground
at certain temperatures and when airborne. We have a trademarked filtration
system comprising of a Sprayguard impregnated filter basket fitted to
our Raincatcher filter unit that will alleviate most fears.
Are pumps expensive to run?
Our raincatcher systems use the lowest costing pumps to run in the industry.
One of our pumps costs under £1 per year to run. We incorporate
pressure vessels when appropriate to stop pumps roaming, which in turn
reduces elecricity use.
Rainwater Harvesting can form a key integral part of a well designed sustainable
drainage scheme, it is often regarded as the first SUDS solution to be
investigated
We have spent the last six years building a flexible and innovative range
to suit all domestic rainwater harvesting needs. Our Raincatcher systems
are British manufactured, not expensively imported from Germany. You can
purchase parts individually or complete packages.
Uses for harvested rainwater:
• Toilet flushing
• Laundry applications
• Garden irrigation
• Car washing
• General cleaning or Water Savings
• Agricultural cleaning
• Animal watering
• Commercial non-potable uses
A family living in a house with four occupants can save approximately
66 cubic metres of water per annum. Water costs vary across the country,
however a payback period for an installed Raincatcher system is generally
between 5.5-6 years. The long term cost of water is predicted to massively
increase, thereby reducing the payback period over time.
Click here to view individual rainwater harvesting component parts
Click here to view commercial rainwater harvesting complete systems
.Other Benefits
• Irrigation use during hosepipe bans
• Improved feel to laundry using soft rain water if you live in
a hard water area
• Reduced risk to increasing water prices
• Higher ratings for BRE and Sustainable Homes assessments
• Cost-effective
• Complete system, including tank(s), filter, pump and header tank
(gravity feed system)
• Simple installation
• Meets Building Regulations Part G 2009 for mains water use in
the home
• Complies with The Code for Sustainable Homes, achieving credits
for two categories (Water and Surface Water Run-Off)
• Possible 6 credits available for WAT 1 and WAT2 accreditation.
• Code for sustainable homes SUR 1 qualifications
• Designed in accordance with BS8515:2009
Installation Costs
For a new build installation costs of a rainwater harvesting system are
low. The majority of tasks required to install a rainwater harvesting
system have to be done anyway for a new build. The largest additional
task is excavating the tank hole. This cost will depend on whether you
have to take away the excess materials excavated with the initial hole.
Laying drains is not an additional task in a new build. One new service
duct from the tank location to the location inside the house where the
control unit is to be located is required. Internal piping for rainwater
harvesting is installed according to standard plumbing best practice;
the only difference is the rainwater harvesting appliances require a dedicated
piping network originating from the rainwater harvesting control unit.
The extra plumbing over and above that of a new build will usually be
no more than 25m. Hook-up and commissioning of
Housing Associations
The costs associated with installing a rainwater harvesting system can
be greatly reduced if the system is able to share components, shared tanks
are a good option where there is the possibility of a landlords supply.
Terraced roofs have to have separate downspouts in order to harvest rainwater
appropriately.
Commercial System - direct feed
A direct feed system is ideal for developments of flats and apartments
without a loft space, or houses and developments that do not have the
need for a header tank.
The recycled rainwater is pumped from the tank and benefits from operating
at the same pressure as mains water, to supply toilets, washing machines
and garden hose pipes.
There is an automatic top up feature which draws mains water into the
tank in the unlikely event that the tank runs dry.
Commercial System - gravity feed
This alternative to the direct feed system uses a header tank or loft
tank. It is ideal for housing associations, or where there is a requirement
for a header tank. The tank has a mechanical mains top up which does not
rely on power to operate, and switches automatically to mains water if
the tank is low. Also it is only the header tank that tops up, not the
main tank
Commercial system includes:
• Tank(s) either above or below ground
• Submersible pump
• Valve and float switch
• External filter
• Header tank with mechanical mains top up (gravity system only)
Exclusive systems to Combined Harvesters Ltd
Our complete ‘from conception to completion’ Raincatcher service
includes.
• An initial site survey to ascertain your individual needs
• On-going technical support during installations with qualified
fitting instructions, DIMS and mobile technical verbal support
• After sales support
• Full on-going qualified maintenance programmes.