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F-Line 7500 Litre Rain Backup in a Box System

F-Line 7500 Litre Rain Backup in a Box System

F-line Flat Tank 7500 litre underground domestic rainwater harvesting system kit with mains backup. The unique F-Line flat tank, supplied complete as a kit for use as a garden rainwater harvesting system. Collect, filter, store and pump for your valuable garden plants and to flush toilets. Mainland UK delivery included

More details...

£ 2,879.73

Tax excluded

F-Line Flat Tank 7500 litre with Mains Water Back Up system includes a 7500 litre underground tank, inline filter and overflow kit, Hydroforce Series 3 pump and the accessories needed to deliver clean rainwater to a garden tap and to flush  toilets. Some standard Back up in a Box shown with float switchexternal pipework and connectors will be needed but are not included in the kit as the location of the system will determine the amount of pipework required.

Why buy this system?

  • Our Rainwater Harvesting systems are based on the highest quality, rotationally moulded, one piece tanks, installed without the need for concrete, thereby minimising installation costs and supported by our long term 25 year tank guarantee.
  • Minimum installation depth
  • Easy and quick to install
  • Small excavation pit and little earth excavation preserves your garden
  • Ideal for installation in new or existing properties
  • Can be installed in ground water up to tank shoulder
  • Prefitted filter, Calmed inlet, and overflow siphon
  • Automatic mains top up with the Rain Backup in a Box®  

The Rain Backup in a Box® is pending WRAS Approval and fitted inside the building where the occupiers can see and hear it. 

WRAS Approval demonstates compliance as it is granted directly by representatives of the water suppliers. It is accepted by every water supplier in the UK.

Limitation on Use: Note that the Rain Backup in a Box® is intended for domestic and light garden use. If you run two garden taps with a high power pump (like the HydroForce, Steel Pumps or Divertron 1100 watt pumps) then the outflow of water is higher than the inflow from the backup device. When the underground storage tank is empty the pump will have no water and its dry-run-protection will turn it off. Some pumps need resetting at the main in this case which is tedious. Most users get round this issue by having mains water taps available alongside the rainwater outlet so that they can switch to mains for garden use when the underground tank is empty. The Rain Backup in a Box® will continue to keep up with demand in the house for toilets and washing machine.


  • The control unit is 370mm wide, 270mm high x 100mm deep
  • Float switch cable length 10m minimum

Easy to install

The F-line flat tank can be installed into much higher water tables than a standard round tank. If you don't know what your water table will be like in the winter, you're safer to install a flat tank. The F-Line tanks are flat and the installation depth is 60% less than other rainwater tanks. The excavation can be up to 70% less, meaning little earth excavation, easy handling and less cost for you! The small excavation pit is easily filled in and your garden will look just like it did before.

Click on this image to see the whole installation

You get 25m of 25mm HDPE pipe with this kitExternal HDPE Rainwater Pipe included. It is important to identify a source of a water supply. Untreated rainwater is not for human consumption and so water companies are recommending (and in some cases requiring) that Black and Green HDPE pipe is used for piping rainwater from the tank to the point of use - eg. garden tap. The point of use should be clearly labelled to show that rain water is the source. We include 25mm black and green hdpe pipe and labels with this kit with the option to buy further rolls of pipe.

Our service.

At Rainwater Harvesting Ltd we provide a'' Complete Solution'' supplying everything specific to Rainwater Harvesting.* There are no hidden extras. We manufacture systems and pumps etc ourselves and hold everything in stock. Delivery is usually within 5 to 7 working days of ordering.

We provide a full time, fully trained technical help desk to answer any questions that the client, builders or plumbers may have before, during and after the install.

F-Line Tanks have a 25 year manufacturers warranty.
All other parts have a 2 year warranty.

Technical Details

Size 1500 3000 5000 7500
Weight Kg 80 170 250 310
Length 1200 2400 2960 3340
Width 2400 2400 2220 2310
Overall Height* 1015 - 1415 1015 - 1415 1350 - 1750 1415 - 1815

Ground to Invert**

320 - 720 320 - 720 345 - 745 310 - 710
Invert to Outlet 162 162 162 162


Size 1500 3000 5000 7500
Length 1600 2800 3360 3740
Width 2800 2800 2620 2710
Overall Height* 1115 - 1515 1115 - 1515 1450 - 1850 1515 - 1915

*Overall height allows for 100mm compacted aggregate

**Using a VS60 (635mm Shaft)

The overall height difference above is because up to 400mm can be cut off the 635mm shaft on site so as to achieve your exact invert level.

* Please note that the pump supplied with this system has a minimum operational throughput of 10 L / minute. If the flow drops below this then the pump will potentially hunt or go into dry run protection mode. If you are using for example a drip feed irrigation system or low flow devices with this pump then we recommend installing a pressure vessel.

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