Graf Carat tank 6500 litre underground rainwater harvesting system kit. The trusted Carat from Graf, supplied complete as a kit for use as a domestic household or garden rain water harvesting system. This complete system features an auto-mains back-up.

The graphic image above shows the main components of the Carat DUK2 System and a typical layout for a simple domestic and garden application. The item marked with a * is the Rain Backup in a Box®. This 12v automated valve will trickle mains water into the tank when it is very low due to sustained drought to allow the connected domestic appliances (e.g. toilet) to work. Read more about this control system here

For further images that give the scale of the product and show some of the fittings please click here.

External 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.

Why buy this system?

• Home and Garden Use
• Feeds garden tap and toilet cystern(s) 
• Automated mains water back-up in case of long drought
• Prefiltered rainwater delivered to the underground tank
• Quiet (pump submerged)
• Pressure sensitive pump only works when tap opened
• Lifting kit not necessary - can be man-handled onto the site
• Exceptionally strong but light two piece Duralen moulding
• Time tested and backed by a 15 year manufacturer warranty
• Tank construction allows for manoeuvre into less accessible locations -even though doorways
• Components precision made and matched for fast assembly

What comes with this kit?

Components list for Graf Carat tank 6500 litre DUK2
Product Code	Product Description
GF-372004	Graf Carat tank, underground 6500 litre
GF-371001	Carat dome (turret)
GF-371010	Carat lid, telescopic, made of PE (green)
GF-330192	Calmed inlet (into base of tank)
27-20-25	1" Strainer
GF-330108	Overflow siphon (high water level outlet, fits filter)
GF-371033	Carat 6500 accessory pack including tank sealing kit
GF-650021	Carat tank dome sealing kit
GF-340037	Graf Optimax Pro Filter
RWH-HYD01	Series 3 Submersible pump and inline filter from Hydroforce Pumps Ltd
RWH-HDPE25/25	Rainwater pipe HDPE 25mm diameter 25 metre coil
RWH-BUB01	Rain Back Up in a Box
Delivery	Haulage, UK mainland included (Highlands & islands on request)
GF-372004-DUK2	Complete Underground kit for domestic use

Graf Carat tank 6500 litre, Complete System 2 underground KIT includes a 6500 litre underground tank, Optimax Pro filter, Enviro pump and the accessories needed to enable you to capture rainwater, filter it and store it at steady temperature ready for use in the home - e.g the flush a toilet - or in the garden to irrigate, power wash, top up water features etc. Some standard external 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.

Graf Optimax Pro filter included as standard
In response to customer demand, we have included the Graf’s Optimax Pro filter which fits neatly inside the turret of the Carat tank. With its integrated overflow siphon and inlet calming device, we no longer need to cut holes in the turret other than those provided by Graf in the moulding.

The Optimax Pro Filter is self cleaning -  water arriving across the filter mesh pushes excess debris and leaves to the overflow. The optional extra hose connector permits you to connect a hose and wash it through more thoroughly from time to time. 

If you are referring to the Graf catalogue or brochure, this kit from RainWater Harvesting is the equivalent to the Graf Eco Plus Package; our kit includes items 1) the Tank 2) the dome or “turret” and 3) Filter package 3. In place of the Graf pump package we provide the high quality, popular and more reliable Series 3 submersible pump, and a inline filter to take the cleanest water first. 

In the kit version, collated for you by RainWaterHarvesting.co.uk, you get the tank, the Optimax filter pack and the accessories listed below.

Upgrade this kit - If household water use is a priority you may want to consider a Rain Director driven system instead. There's more information on this rainwater management control system here. 

Optional Upgrades.

1) Bit more leeway on the tank depth: Opt for a Maxi sleeve giving an extra 100mm of adjustment (see above)  Product ID: GF-371011 

2) Support car traffic: (but not trucks and HGVs) when fitted with the optional dome and cast iron lid. Contractors often ask us the dimensions of the turret. The Vehicle loading lid can be found here Product ID: GF-371020

• Height variable between 750-1050 mm.
• Maximum tilt 5%.
• Cast iron cover.
• Child safety lock.
• Dark Grey.

3) Deeper holes: You can compensate for a deep hole with a tank turret sleeve extension Product ID: GF-371003 which extends the height of the pedestrian dome shaft by 305mm

More Research?

Manufacturing expertise
The Graf Carat tank is the largest tank of its kind in the world to be manufactured by injection compression moulding. This technique provides the tank with unbeatable stability and ensures that each component is produced with the highest accuracy. Graf have invested €20m in their factory near Freiburg for the Carat range, introduced in early 2007.

Shipping, assembly and installation
Like the Graf Hercules, the Carat comes in two halves so you can carry it through a doorway as narrow as 80cms (and so we can stack many of them on one pallet for bulk transport). A centering bolt in the flange makes assembly accurate and the knock-on quick connections and patented seal ensure there are no leaks between the two sections... and yet you can disassemble it if you like. The material used is a PE variant called Duralen.

Designed for underground mounting 

(German manufactured, TÜV safety-tested)

Patented quick connection (no screws required for mounting)

Permanently watertight: durably sealed thanks to solid profile sealing

Easy transport thanks to low weight and practicable size

Durably sealed thanks to solid profile sealing

See table for dimensions and weight

Compare the Carat S Tank sizes
Tank	2700 Litres	3750 Litres	4800 Litres	6500 Litres
Product Code	370001	370002	370003	370004
Weight	120 kg	150 kg	185 kg	220 kg
Length	2080mm	2280mm	2280mm	2390mm
Width	1565mm	1755mm	1985mm	2190mm
Height	1400mm	1590mm	1820mm	2100mm
Total Height	2010mm	2200mm	2430mm	2710mm
Half Height ie before assembly (for access)	700mm	790mm	910mm	1050mm
Go to other tank sizes	Go to a 2700L system	Go to a 3750L system	Go to a 4800L system	You are here

Connections for underground installation: we supply the tank as in the Graf Eco Plus package, with recesses where holes for piping need to be cut.

• Like a bigger tank with the same fittings? Try here
• Download a technical drawing of the Carat 6500 litre tank by clicking here
• A detailed catalogue on the Carat tank range can be downloaded by clicking here.
• Watch video on assembly of Carat tank by clicking here
• Download a Carat tank installation guide by clicking here
• Go here to download the installation instructions including schematic drawing for the Back up in a Box in pdf format
• Otto Graf in Germany have a wealth of technical data and application illustrations on their website, including downloads and videos. To visit the Graf website please click here>