Rainwater recycling: Types of control systems

Background and introduction

Rainwater recycling or rainwater harvesting as it is more commonly known is a fairly well mature technology that was developed during the last thirty years. Essentially the storage and filters quite simple. But the control systems are more complex driven by the need for reliability. In the UK, we have mostly thanks the Victorians enjoyed a safe and reliable water supply for the last hundred years or so. It's really in the last fifteen years where terms such as water stress has started to be used. The Environment Agency suggests that everywhere south of the Humber estuary is under some form water stress and of course the drier south and south east is continuing to see an increasing population.

Types of controls

There are three main catagories of controls with most rainwater harvesting systems.

1. Direct pressure systems
2. Header/break tank systems
3. External use only (Gardening) systems

Direct pressure

Direct pressure systems work by supplying water at pump pressure directly to the point of use via a control panel. This panel also controls the mains water back-up arrangements, of which there are a number of different configurations between different manufacturers. But all systems must comply with WRAS regulations and this put simply here is concerned with an air gap (type AA) to eliminate direct contact between potable and non-potable water. There are also regulations regarding pipework identification.

These systems are normally installed in lower demand situations such as domestic single dwellings. Where the demand is much higher, more than one pump can be used as duty standby assist type arrangements.

Header/break tank

These systems differ slightly from the direct pressure systems as the main pump or pumps send the water to a header tank (gravity system) or to a plant room based break tank. Where required additional pumps are used to boost the water supply around the building. These types of systems tend to be used in more commercial/industrial projects. Similar water regulations also apply to these systems and a slot/ cut-away (AB type airgap) is also required.

Garden rainwater harvesting

These systems were developed in response to the hose-pipe ban/water restrictions that were in place arouns 2006 (UK). They tend to have a lower specification generally, and most importantly the mains water top-up arrangements are usually excluded to protect the end user from falling foul of the water restrictions.

At Freerain Ltd, we have developed numerous various on the themes above to suit the project requirements and indeed are contuning to develop new ways to improve the performance and interface with BMS systems and other systems. More information about commercial rainwater harvesting system can be found on our website.