Gravity Fed, Rainwater Harvesting System, 8400-GFL

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A complete domestic gravity fed rainwater harvesting system with mains water top-up.

This system has everything you need to filter, store, and pump rainwater to the point(s) of use. All you need to supply is the rainwater collection and distribution pipework.

This 8,400-litre domestic gravity-fed system is generally suitable for large projects, and these are typically installed into a 4 bedroom dwelling.

Rainwater storage tank

Our 8,400-litre underground storage tank is complete with a pedestrian rated telescopic neck (extendable by up to 300mm), pedestrian rated lid, push fit DN100 drainage connections, in-tank-filter, and calmed inlet.

Made from polyethylene plastic in the UK, it has a unique ribbed design for extra strength. Thanks to its low profile design, only a shallow dig depth is required. It most cases it can be installed without the need for concrete.


In-tank rainwater filter

The system is supplied with a choice of 3P Technik in-tank filters:

1) Compact filter suitable for roof areas up to 150M2


2) PF filter suitable for roof areas up to 200M2


3) VF1 filter suitable for roof areas up to 450M2 (twin neck tank required)


The filter is pre-installed into the neck of the tank, where is it joined to the also pre-fitted calming inlet.

This filter removes leaves, grit, and other debris from the incoming water up to approximately 1mm.

Finer particles form a “scum layer” and are washed away during overflow or filtered out by the secondary filtration.

The filter is easy to clean. There are no consumables- just lift, rinse, and replace for continued use.

Twin neck tank option

This tank has a twin neck/access opening option, which is supplied with 2 x telescopic necks and 2 x pedestrian rated lids.

Due to the size of the tank, we recommend this option for better tank and interior component inspection and maintenance.

However, the twin neck tank is a must if you opt for the VF1 filter.  Due to the size of the VF1 filter, it will fill the access opening completely which leaves no room to inspect or maintain the interior of the tank or any internal equipment.


DAB submersible pump

This system is supplied with a highly reliable DAB Divertron 1000m submersible pump.

It delivers approximately 4 bar of pressure and up to 3,500 litres/hr of flow.

The pump starts and stops automatically by its integrated control system. It has dry run protection, a built-in non-return valve, and a screened filter as standard.

It is suspended from a pre-fitted hook in the neck of the storage tank by a stainless steel chain.  It comes with a high-quality large handle, for easy lifting when if necessary.


Gravity-fed controls

This system also known as an indirect pressure system, uses a header tank that needs to be installed in a location higher than the point(s) of use. In most installations, this will be in the attic space of a building.

The gravity controls are pre-fitted inside the header tank along with pre-drilled inlets and outlets.

The header tank is delivered to site assembled, tested, and ready to install.


How does it work?

Water is pumped to the header tank from the storage tank via the submersible pump.

When demand is placed on the header tank, water is gravity fed to the point of use.

Our header tank has a mechanical delay action; this means that a WC or similar demand can be flushed 4-5 times before the pump starts and fills the header tank completely in one go.

Should the underground tank become low, the header tank will continue to be depleted until the level has reached the main water top-up level.  At this point, mains water is introduced directly to the header tank.

As the pump is starting and stopping less frequently than with direct pressure systems, the power consumption along with wear and tear of the pump will be much less.

Key Features

  • Manufactured in the UK
  • Large stock ready for quick dispatch
  • Shallow dig depth underground tank
  • Optional in-tank filters
  • Easy clean filter
  • DAB submersible pump

Tank Specifications

  • underground storage tank installation information 5200 10000l
  • Capacity litres:  8400
  • Capacity gallons:  1848
  • Length mm:  3870
  • Width mm: 2700
  • Height (not including tank neck) mm:  1250
  • Access entry mm:  600
  • Weight kg:  390
  • Material:  Polyethylene
  • Potable: No
telescopic tank neck specs
Telescopic tank neck

Pump Specifications

DAB divetron 1000 m Performance Dimensions

DAB divetron 1000 m pump curve

System Includes

  • Underground storage tank
  • Telescopic tank neck
  • Pedestrian rated tank lid
  • Pre-fitted In-tank calmed inlet
  • Pre-fitted In-tank Filter
  • Pre-fitted push fit DN100 drainage connections
  • DAB Divertron 1000m submersible pump
  • Inline strainer assembly
  • Header tank with pre-fitted controls
  • 15 meters of 32mm rainwater pipe
  • Marker tape and ID pack

Additional Information

The rainwater harvesting system is delivered complete with the components as listed.

All you need to supply is the DN100 pipework from the building’s downspout to the storage tank along with DN100 pipework to connect the storage tanks overflow to the storm drain.

In addition to the DN100 pipework, you will also need to supply the pipework from the inline strainer assembly to the header tank and to the point(s) of use.

However, there are additional components available that are listed in the dropdown menu at additional costs.

If you can’t find what you are looking for or require further information please contact us.

Rainwater Harvesting Service & Maintenance

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