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Rainwater harvesting is simply the collection and storage of clean rainwater for reuse.
When it rains, water runs off impermeable surfaces, into a drain, we often forget that it has to go somewhere. Lots of water causes flooding which is what we aim to control.
Every drop that we can store and reuse is a drop less that can reduce flooding. We need to look at where we can use water that would otherwise come from the tap and cost us money, such as irrigation, toilet flushing, car/plant washing etc. Did you know that a typical garden sprinkler uses around 1,100 litres of water per hour?
The concept is simple, intercept one or more of the downpipes from your home or work premises and direct this to a tank, from here you can pump it to provide almost free water and help the environment. This can start from a simple home kit to a fully integrated tank with pre-filtration and a water treatment system, the water can then be pumped and used for toilet flushing in homes and schools, watering lawns and gardens, feeding livestock, washing cars and plant etc.
The use of harvested or non-potable (non-drinking) water has recently increased as the cost of water has risen and we have become more concerned about our environment.
200 Series
(1.2m internal diameter):
1,000 – 10,000L capacity
300 Series
(1.8m internal diameter):
4,000 – 40,000L capacity
400 Series
(2.6m internal diameter):
13,650 – 100,000L capacity
500 Series
(3.5m internal diameter):
60,000 – 200,000L capacity
600 Series
(4.0m internal diameter):
100,000 – 300,000L capacity
Designed with reference to BS EN 13121. All tank shells carry the SPEL 25 Year Warranty and life expectancy in excess of 50 years.
Different tank shell specifications are available dependent upon tank invert levels, ground conditions and ground water levels.
Pipe connections available to
accommodate most standard sizes.
Water reuse is at the top of the SuDS hierarchy meaning it will become more important as the planning authorities insist on good SuDS being included in all new developments; this will be endorsed with the enacting of Schedule 3 of the 2010 Flood and Water Management Act.
Lead Local Flood Authorities (LLFAs) are implementing Schedule 3 with planning applications being checked for the inclusion of more robust SuDS design and compliance across the 4 Pillars, making Rainwater Harvesting more important than ever.
If every family in the UK harvested 1 litre of rainwater per week, it would save over 1 billion litres of water every year, this could be greatly increased if we get businesses, schools, and transport systems to do the same.
The objective is to provide a system that maximises the available suitable catchment area, and provide economic and efficient storage capacity as well as treatment most suitable for the final use.
For catchment areas, roofs are the best, although hard standing such as car parking and aircraft aprons can be included. The risks with hard standing areas are the possible additions of hydrocarbons and faecal material into the system.
Pre-filters are strongly recommended to remove leaves and other debris prior to storage. The SPEL Tankstor rainwater storage tanks incorporate a calmed inlet, and an overflow with an anti back flow valve to prevent contamination. There is also a float pump that collects water from the top 100mm of stored water (this is the cleanest water). The larger systems have larger pumps with associated pedestals, guide rails, pipework and valves ‘factory fitted and tested’. Dual/triple pumps can be duty/ assist or duty/standby.
The first stage of treatment is the SPEL pre-storage filter. Two models are available; the SPEL RainSave Debris Filter Chamber and the SPEL RainSave In-Tank Debris Filter, both of which can be tailored to suit site conditions and/or design constraints.
These incorporate a stainless steel mesh filter with a mesh opening size of 1mm. The filter is easily removed for maintenance. These filters prevent leaves and other solid debris entering the tank. For some applications, further treatment may not be required, however for any application involving human contact (or close contact), further treatment is required.
The SPEL RainSave Debris Filter Chamber is a completely separate unit to the storage tank. It is available in a range of diameters but is usually provided as a 1.2m internal diameter chamber. It incorporates a stainless steel mesh filter with a mesh opening size of 1mm. The main advantage of this unit over the intank option is that it has larger debris capacity for longer periods between maintenance, but also flexibility of inlet, outlet and overflow diameters and positioning is available.
The SPEL RainSave In-Tank Debris Filter is a cylindrical basket with a 1mm mesh opening size. Firstly, the water enters an extended shaft on the top of the tank before making its way through this mesh filter. It then discharges down into the rainwater tank. The advantage of this system is that it is delivered to site as a complete tank with integrated pre-treatment. In shallower excavations, the space required for this may not be available. Also, due to this unit being situated on the tank, the overflow pipe can be fitted in a limited number of locations, to avoid other tank access shafts.
The SPEL Tankstor range of tanks are incorporated into SPEL RainSave Systems. Designed in accordance with BS EN 13121.
SPEL Tankstor underground tanks are manufactured by the technically advanced chop hoop filament winding process, the tank shell is also covered by the SPEL 25 Year Warranty and life expectancy of up to 50 years. Capacities range from 1,000 litres up to 300,000 litres in a single unit.
It is advised that storage tanks are below ground as the water temperature is kept at a level that ensures less degeneration of water quality.
SPEL offer three systems for transporting the harvested rain water from the tank to its point of use. 1, the SPEL Direct System pumps the water from the tank via a treatment unit direct to its point of use. 2, the SPEL Indirect System pumps water via a treatment unit to a header tank from where it can be distributed. 3, the final option is the SPEL Stand Pipe System which pumps direct from the tank to the point of use with no treatment.
A slim design control panel that comes to site ready to be fitted into the plant room via it’s one-piece structure (package system), and controls the system automatically with a digital display showing the system status.
Two stage particulate treatment captures particles down to 5 microns across two separate filter units, ensuring longer life between replacements.
Water passes the UV lamp after passing through both particulate filters, this ensures maximum bacteria reduction providing high quality, non-potable water. The control system ensures the UV lamps are running at optimum performance and alerts when UV lamp replacement is required.
Works to protect the pumps and supply consistent pressure.
Ensures correct pressure is maintained and warns of system pressure loss.
Bespoke SPEL RainSave Pumping and Treatment Systems are available with optional extras, including features such as:
Each of the SPEL RainSave options on the next page have a pumping element and SPEL have a number of pump flows available:
3 bar is the standard operating pressure, other pressures and flow rates can be provided by SPEL to suit specific site requirements.
The SPEL RainSave Pumping and Treatment Systems pump the water from the Rainwater Storage Tank via a control panel, this treats the water before it is pumped to its destination. Full details of pumping volume/pressure and treatment options can be found on the previous page or by calling our technical support team.
Rainwater is supplied direct under pressure from the storage tank simplifying plumbing and removing the need for a header tank. This system is typically used for irrigation and vehicle or plant washing. Mains backup can be connected the storage tank to ensure continuity of supply. The direct system always has a dual pump system in to provide continuity in case of pump failure to ensure continuity of supply.
When mains water is piped into a tank or similar, a ‘Type AB’ air gap must be provided to ensure the water in the tank does not cross contaminate the mains water pipe. Four options are also available to achieve this air gap:
The SPEL RainSave Indirect System pumps to a header tank, which also allows the mains backup to be simply connected to the header tank. This is usually a single pump system (dual pump available), as supply is less reliant on the RainSave pumps. This allows for a dedicated booster system and for easier retrofitting of rainwater harvesting systems.
The SPEL RainSave Stand Pipe System is a much simpler system with no control panel and simply pumps direct from the tank to wherever the water is required. Pumping flow rates and pressure detail is covered on page 39. This system needs careful consideration as the only treatment of the water will be by the pre-tank debris filter therefore finer particles, bacteria, and harmful cloriforms may be present. Risks such as legionela, keeping untreated water away from humans, and particulate staining, must be considered.
SPEL Products provide drawings for approval for the Tankstor storage tank and associated pre-filter. Installation should be carried out in accordance with the SPEL Installation Instructions in the SPEL Data Manual Section 8 and the other elements (electrical, plumbing, etc.) in accordance with good practice and appropriate regulations.
On completion of the installation and confirmation that the electrical power supply is connected and available for the SPEL RainSave control panel/skid position together with the mains water back-up supply (if applicable), a SPELGuard engineer can visit site and commission the system if required.
| Type | Run-off | Depression Storage* |
|---|---|---|
| Pitched roof with profiled metal sheeting | 0.9 | 0.1 |
| Pitched roof with tiles | 0.8 | 0.3 |
| Flat roof without gravel | 0.8 | 1.0 |
| Flat roof with gravel | 0.8 | 1.0 |
| Green roof, intensive** | 0.5 | 5.0 |
| Green roof, extensive** | 0.7 | 4.0 |
| Permeable areas, various** | 0 – 0.3 | 2.0 – 4.0 |
*Volume of water lost from surfaces, eg. by evaporation or absorption before run-off commences.
**The run-off yield is uncertain for these surfaces and depends on their design.
| Tank size (litres) = | 20 days storage x annual usage | = ………… litres |
| 365 |
| Tank size (20 days storage) = | above m³ | = ………… m³ |
| 18.25 |
| Ratio = | Catchment area (A) x Annual rainfall (R) | = | AR |
| Annual demand (D) | D |
This is the operation of the SPEL RainSave Direct System. For more information on this system and also to see SPEL’s two alternative Rainsave systems, see the SPEL Rainsave Pumping and Treatment Options above.
Lancaster Road
Shrewsbury
Shropshire
SY1 3NQ, UK
