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Rainwater Harvesting


How it works

The AswaRain Harvesting System from Molloy Precast is designed to collect, store and recycle rainwater for use in anything from a domestic house to a large commercial premises. Each system is custom engineered to ensure optimised performance, reliability and cost effectiveness.

How the Aswaflow System works

1. Rainwater collected from roof

Rainwater is a free natural resource which you can capture, store and use in your own home whether it is an existing building or a new build. The existing roof, gutter system and downpipes on an office/warehouse can easily be used to collect rainwater, which flows through a pipe network into the AswaRain system.

2. Rainwater storage

Every AswaRain system is equipped with the following:

Storage Tank – The Aswarain system includes a Molloy Precast concrete tank, which has several advantages over plastic systems. There are a variety of tank sizes available, and it is important that the tank size chosen is suitable for your house. Our engineers will design an appropriate system considering the roof size, rainfall, rainwater application and occupancy.

Leaf Filter – Rainwater will collect leafs and other solids from the roof and gutter system which need to be removed. A leaf filter is fitted on the inlet pipe; this collects all gross solids preventing them from contaminating the stored water.

Calmed inlet – Dissolved solids such as sand and grit will be carried into the system, these pass through the leaf filter unaffected, however, they will settle to the bottom of the tank, hence not affecting the quality of the outflow. To prevent the inrush of water from disturbing these solids a calmed inlet is installed on the inlet pipe.

Submersible pump – Rainwater is pumped from the tank into the premises by a pump positioned off the floor of the tank to prevent the settled dissolved solids from contaminating the house supply.

3. Water pumped to point of use

Water is distributed throughout the premises using a pressurised system. The pressurised system eliminates the need for the header tank, and a pressure vessel is installed to maintain a consistent pressure in the subsequent pipe network. A variety of pumps are available for high or low delivery, depending on the rainwater application.

4. Filtration and Sterilisation Option

Gross and suspended solids are removed by the basic Aswarain system; however other contaminants such as colloidal solids and pathogens may remain in the rainwater. This water is perfectly suitable for use in toilets, irrigating gardens and for washing cars. For those who wish to use rainwater for hygiene purposes,  Molloy Precast offer an optional treatment system which will produce a water suitable for use in washing machines, and as hot water for showers and sinks. This treatment system filters out dissolved solids and subsequently sterilises the rainwater using the following equipment:

Pressure vessel – This device ensures a consistent pressure is maintained through the subsequent equipment and hence pipe network. This will reduce the risk of damage to these and other devises connected to the system

Course and fine filter – This system removes all colloidal solids from the rainwater ensuring the UV light operates to its maximum potential.

UV light – The UV light kills all pathogens in the rainwater providing a clean water supply. Sterilisation is instant and is not residual, meaning that contamination can occur further down the pipe network.

5. Excess water via bypass to Soak Pit

To prevent overflow of the Aswarain system in times of heavy rain, a storm bypass can be incorporated in the design. This allows excess water to bypass the system once the storage tanks have been filled. The excess water can then join the on-site storm water attenuation system.



Commercial Systems

Molloy Precast offer a range of Aswarain systems. It is important that each system is sized appropriately to enhance operation and increase cost effectiveness. Our engineers will consider your roof size, rainfall, applications and occupancy to ensure you are provided with an appropriate system. We manufacture large variety of precast tanks for a wide range of uses; this allows us to combine different sized tanks to provide you with an accurately sized system. Below are four standard systems; however our design team would be happy to design an individual system to suit your needs upon request:

Aswarain® 2S+
  Volume: 14000 litres
  • Ideal for wet sites and deep installations
  • Simple installation, no concrete back fill required
  • Example application: Farm/Small Factory
Aswarain® 3S+
  Volume: 21000 litres
  • Simple installation, no concrete back fill required
  • Example application: Schools
Aswarain® 2D
  Volume: 30000 litres
  • Large storage capacity
  • Example application: Washing facility
Aswarain® 3D
  Volume: 45000 litres
  • Provides large water reserve
  • High storage capacity suitable for large roof area
  • Example application: Warehouse/Large factory

Featured Projects

  • Commercial
  • Industrial
  • Schools

See below a sample of commercial projects in Ireland with Molloy Precast Rainwater Harvesting Systems.

  • 2nd Offaly Scouts Den, 7000 litre
  • Clara Nursing Home, 30,000 litre
  • Aura Lesiure and Swimming Pool, Tullamore, 15,000 litre

  • Kilcormac GAA

See below a sample of Molloy Precast Rainwater Harvesting Systems installed for usage in industry.

  • Boston Scientific, Cork
    30,000 litres
  • Tesco Tramore, Waterford,
    8,000 litres

See below a sample of National Schools in Ireland with Molloy Precast Rainwater Harvesting Systems.

  • O' Brennans N.S. Tralee, Kerry, 15,000 litres
  • Clara N.S., Offaly 7,000 litres
  • Rhode N.S., Offaly,
    8000 litres
  • Birr / Crinkle N.S. Offaly
    18,000 litres


The benefits of rainwater harvesting:

  • Reduce your water charges. Rainwater is completely free!
  • Rainwater harvesting is environmentally friendly
  • Rainwater is soft water which means lime-scale free appliances
  • Chlorine free rainwater helps prevent rust on appliances

What Molloy Precast offer:

  • Unrivalled expertise & advice
  • A product and service from a long established company
  • Durability of a concrete system – exceeds 50 years