Rain water recycling

Basic rainwater recycling

The simplest approach to recycling rainwater is to fit water butts under existing downpipes. This can be very cost effective and surprisingly efficient. Most water butts are designed to store 200 + litres of water which can wash the average car 10 times if used with a bucket or, water the average person’s vegetable patch for a couple of days. Costing between €60 and €125 each including fitting for basic models this simple solution is often the only one that can be justified within the average budget.

The more committed rainwater recycler is going to be looking at a system that can utilise far more of the rain which falls on their property which brings us to-

Rainwater Harvesting which is the process by which water which falls onto the roofs of buildings is collected, filtered and transported to a point of use. It can provide a useful alternative to mains or well pumped water supplies and can have benefits in the attenuation of rainwater that would otherwise enter drains and soak-aways

Basic types of Rainwater Harvesting system;

There are three principal types of Rainwater Harvesting system

  • Direct System:-

    This is where rain is collected from gutters, filtered and stored in a tank from which it is pumped under pressure to its intended point of use.

  • Gravity and pumped system:-

    This is where the water is pumped from the tank after collecton and filtration to an elevated cistern usually within a building from which it flows to its point of use by gravity.

  • Basic gravity system:-

    This is where water from the tank after collection and filtration is allowed to make its way under gravity to its point of use

  • Component parts of a Rainwater Harvesting system;

    All Rainwater Harvesting systems require similar basic components:-

  • A tank or reservoir
  • A filter to prevent leaves and debris entering the tank
  • A pump (for most systems)
  • A means of topping up the tank in the absense of rainfall
  • An overflow to allow excess water to escape to a drain
  • Other components may be:-

  • A cistern, usually in the attic for gravity and pumped systems
  • A device to switch over to mains supply in the event of a system failure
  • A monitoring system, to allow control and keep track of levels
  • There are others but this covers most systems

    Tanks; There are several options but the first choice is whether to go above ground or below ground?

  • Above ground;

    These can be made of plastic, GRP (glass reinforced plastic or fibreglass), concrete or even metal (if treated to prevent corrosion)

    In favour of this option is that they are generally cheaper, quicker to install and easier to access. Against this they are bulky, possibly unsightly and if not protected from the sun potentially capable of encouraging the growth of pathogens like Legionella which thrive if the temperature rises above 20 degrees c.

  • Below ground;

    These again can be made of plastic, grp or concrete. In their favour underground tanks take up no floor space (other than access panels), are not visually intrusive and offer protection from unhealthy temperatures and so minimise the risk from Legionella etc. Against this they are much more expensive to purchase and install, create more disruption during installation because of the excavation and underground plumbing and are more difficult to gain access to in the event of a problem.

    Filters;

    These can be made of plastic or stainless steel and are designed to separate the bulk of contaminants without reducing the amount of water entering the tank. To meet with BS.8515 requirements all filters for Rainwater Harvesting systems should be

  • at least 90% efficient
  • capable of removing all particles larger than 1.25mm
  • weather and fully water resistant
  • and easily accessible for maintenance and cleaning
  • They should also prevent rodents or other pests entering the reservoir and where possible allow overflowing surplus water to carry off debris to the drains.

    Pumps;

    There are two basic types of pumps for use in these systems

  • Submersible pumps;

    these are generally made of plastics and stainless steel and are designed to be permenantly immersed below the water surface in the storage tank. They are usually fitted with a float switch to prevent dry running and may incorporate a floating intake designed to extract water from 100 to 150mm below the water surface where there is little chance of sediment or floating debris.

  • External booster pumps;

    these are fitted outside or even away from the tank and are plumbed in such a way that they draw water from an outlet near the bottom of the tank (which may be connected to a floating intake wthin the tank) and boost the pressure sufficently to reach its point of use or storage cistern depending on the type of system employed. They can be fitted with anti dry run devices but in common with all pumps and some tanks they must be protected from freezing.

    Top up devices;

    It is absolutely essential that there is no risk of water from the Rainwater Harvesting system entering the plumbing carrying potable (treated and regarded as wholesome) water. To prevent this there are strict guidelines governing the ways in which potable water can enter a non potable system such as a Rainwater Harvesting tank. The principal device involved is called a Tundish, this allows water to pass across an air gap conforming to an internationally recognised standard and preventing any back flow.

    Most packaged Rainwater Harvesting systems are equipped with an electrically operated float switch and this in turn opens a remote solenoid valve through which top up water can pass through a Tundish or similar approved device into the rainwater tank.

    Uses for recycled rainwater;

  • flushing of toilets
  • water supply to washing machines
  • irrigation of plants
  • outside tap for general cleaning
  • supply to water features and ponds
  • Tasks which recycled rainwater cannot be used for ;

  • drinking
  • cooking
  • dishwashing
  • personal hygiene
  • We have attempted to keep this brief and simple, if you have any queries that you cannot find answers for on this site please email- info@bearawaterservices.ie

    Click on our gallery links for diagrams and images that may help

  • schematic of a gravity system
  • schematic of a gravity and pumped system
  • schematic of a direct system
  • examples of above ground tanks
  • examples of below ground tank
  • some typical pumps
  • some examples of rainwater filters
  • water butts
  • Comments are closed.