Our Rainwater Harvesting Systems Explained

Rainwater can provide some of the cleanest, natural occurring water that is available anywhere. Most technologies for obtaining water comes from surface water from rivers, streams and lakes, however this only accounts for 40% of total precipitation. Therefore, there is a huge amount of rainfall available for collection before it becomes unusable.

Rainwater harvesting is becoming increasingly popular in the UK for both residential and commercial customers. Up to 50% of mains water used in the UK can be replaced with rain water, e.g. washing laundry, cleaning, toilet flushing and car washing. Most people are starting to see that mains water costs will continue to rise in the coming years and that rain harvesting is an effective, eco-friendly and cheaper way to provide water.

Underground Garden Systems

These garden systems are ideal for collecting and storing rainwater to use for tasks such as watering plants or washing a car. We supply a wide range of these thanks, from 1800 litres to 10000 litres.garden system

All of these tanks come with;

  • Compact filters – pre-installed into the neck of the tanks allowing clean water into the tank by filtering out leaves, grit and other debris.
  • Submersible pump – these are suspended from a pre-fitted hook in the neck of the tank by a stainless steel chain which allows the pump to be lifted out for maintenance.
  • Drainage connections – these allow the drains to be connected into the neck of the tank.

Underground House Systems

We have two types of house systems available;

  1. Direct Pressure System
  2. Header Tank System

They are both ideal for collecting and storing rainwater to use in your home for tasks such as toilet flushing and washing clothes. We supply both of these tanks in a range of sizes from 1800 litres to 10000 litres.

All of these tanks work in similar ways to the Garden Systems and also come with;

  • Compact filter
  • Submersible pump
  • Drainage connections

The difference between the house systems and the garden systems is that the house systems are connected to the mains water supply. This means that if the water level in the tank is running low, the mains water will send a small amount of water to the tank, therefore leaving maximum capacity available for the next rainfall. These are fitted with an AB air-gap to prevent the back-flow of the water into the mains, therefore only allowing mains water to flow into the rainwater tank, and not the other way round.

Direct Pressure System and Header Tank System Differences;

1) The Direct Pressure System
These work by supplying water directly to the point of use, e.g. if a toilet is flushed, the pump starts running and the rainwater from the tank is pumped to refill the cistern in the toilet, once the cistern is full, the pressure in the pipework is restored and the pump automatically stops.

2) Header Tank System3400-litre-ht-system-500x500

These systems use a 82 litre tank fitted into the loft of a house, this is filled with water directly pumped from the rainwater tank. When demanded, water will flow from the header tank to the place needed such as the toilet cistern. Once the header tank is low on water, the pump will automatically start the water flow from the underground tank to refill the header tank. Should the underground tank reach a low level, the mains water supply will fill the header tank directly. This means a longer product life for the pump as it is starting and stopping less frequently compared to the Direct Pressure System.


This process is simple and everything required comes with the underground tanks, including in-depth instructions.

These are the main steps required for installation;

  1. A small excavation pit large enough for the product specification, including the telescopic neck and lid (neck height can be altered to fit into the ground level).
  2. A pipe then needs to be attached to the neck where the water flow will come from, usually from a drainpipe. This will then connect to the in-tank filter than is pre-installed. This filters out leaves, grit and other debris, allowing clean water to filter into the tank.
  3. The submersible pump needs to be attached onto the pre-fitted hook in the neck of the tank and lowered.
  4. A pipe then needs to be fitted from the tank to the water supply, either a tap for the garden systems, or for the house systems, where the water is needed in the house (toilet) or the header tank.
  5. Another pipe then needs to be fitted from the neck of the tank on the outside of the in-tank filter to lead the water away from the tank if it’s unclean or the tank is full.

To view our full range of underground rainwater harvesting tanks click here.