Yield Examples cropFor repeat buyers, Freerain rainwater harvesting systems, or individual components such as tanks and pumps can be ordered online here; however, first-time buyers are advised to read the information below, and Contact Us before placing an online order.

Systems Available

General information about current domestic and garden-only systems is provided on the Users Guide pages; the headings below cover additional factors that system buyers need to bear in mind.

Garden-only systems

Garden-only systems are simplified versions of domestic systems, as explained in the Users Guide. It should be particularly noted that the use of mains-water backup is not recommended with these systems.

Commercial Systems

Freerain no longer provide bespoke commercial systems; however, it should be noted that the larger domestic systems are entirely suitable for many of the smaller commercial applications.

Communal Systems

On housing projects where some of the property sizes do not justify a stand-alone rainwater harvesting system for individual properties, the larger domestic systems are also entirely suitable to be used as communal systems covering several properties.

This is a particularly important consideration where the inclusion of rainwater harvesting forms part of the site’s sustainable drainage (SuDS) requirements; more information on this is provided on the SuDS page.

Off-grid Potable Systems

Harvested rainwater is non-potable, and it must not therefore be ingested or inhaled; its use is therefore restricted to applications such as toilet-flushing, clothes washing machines and garden irrigation.

Where a potable supply of water is required at a location that has no mains water supply, harvested rainwater can be brought up to potable standards by use of additional carbon & UV filtration. This constitutes a “Private Water Supply” which must be notified to the Local Authority who will be responsible for testing that the water is fit for human consumption.

Bringing harvested rainwater up to potable standard is not cost-effective where a mains supply is available due to the cost of the additional filtration, and the un-necessary activation of the mains water back-up that will usually result.

Storage-tank Sizing

To be compliant with the requirements of BS-8515, the Code of Practice for rainwater harvesting systems, the size of the main storage tank for domestic systems is usually determined by a combination of the harvesting potential of the collection roof, and the need to regularly rotate the water through the tank to maintain its aesthetic quality.

The harvesting yield (in litres) for an illustrative range of roof areas and local rainfall conditions are shown in the table above; the figures in “red” show where there is an exact match between the harvesting yield and the Freerain range of tanks.

Where the calculated yield does not exactly match the available tank size, these closest best-match is selected, taking into account property occupancy, and whether consumption of non-potable water is likely to be above or below the norm.

Tank Installation Considerations

Full installation instructions are provided with all systems, but ahead of ordering, consideration needs to be given to factors such where the tanks will be installed, associated over-trafficking, ground conditions, drainage invert levels, and drainage orientations.

Comprehensive information on all these factors, and for all tank-sizes, are available on the Downloads section of this website per the example here.

Header-cistern vs Direct-pressure HT vs DP

It is the buyer’s choice to decide whether a header-cistern or direct-pressure system is best for their particular project.

To help inform that decision, the independent comparison between systems has been provided by the UK Rainwater Management Association; however, Freerain would recommend use of header-cistern systems wherever technically possible on communal systems, or if there is a likelihood that the property will be rented.

Uniquely, Freerain are able to offer either option at the same price.