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GAH Dualstream Direct Hot Water Cylinder - 305 Litre
GAH Dualstream Hot Water Cylinder - 500 Litre

GAH Dualstream Direct Hot Water Cylinder - 305 Litre

Your Price: £3,134.70
Not for Sale
Part Number:TDD305

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Feature 5

Bedrooms:6, Bathrooms:3, Shower Rooms:3

Choosing the Right System

Cylinder ModelCapacity LitresCoil SurfaceCoil RatingmmWeight EmptyWeight Full
TDI 1301300.5420.555022152
TDI 1501500.5426.755026176
TDI 2152150.7526.755038252
TDI 2552550.7531.855048303
TDI 3053050.7531.855057362
TDI 5004951.531.8714149641
TDD 13013055024154
TDD 15015055031181
TDD 21521555038253
TDD 30530555055360
TDD 500495714130630

Storing too much hot water wastes energy and increase running costs, so getting the right balance is important. There are two main factors to consider when choosing any unvented cylinder and that is pressure (the force of water) and flow-rate (the amount of water carried in the pipe-work). There are other factors like the number of occupants and the number of outlets, bathrooms etc and the pattern of usage, along with how you intend to heat the cylinder either by Direct (Electric immersion) or Indirect (from a boiler source.)

Because Dualstream systems utilise the accumulator to increase the flow rate and performance, the greater the amount of cold water stored, the longer the performance can be obtained.

The accumulator Model under average incoming mains pressure conditions is made up of approximately 60% water /40% air charge, so we advise to increase the size of the accumulator to at least one or two sizes larger than the unvented cylinder size, depending on the incoming mains flow rate. For high demand or greater volume, cylinders and accumulators can be linked in parallel. This method is ideal for the larger properties and leisure-sports facilities. And unlike standard unvented cylinders that are totally reliant on the mains supply Dualstream systems can bank the accumulators to create the cold volume to run the unvented cylinders regardless of the incoming mains flow rate. The sizing chart is a guide to choosing the correct combination of Cylinders, but should you require expert advice please call us.

Accumulator model options


Cylinder size

100 - 200 - 240

1-2 bed, 1 bath/shower, kitchen

125 litres

200 - 240 - 300

2-3 bed, 1 bath/shower, kitchen, cloakroom

150 litres

240 - 300 - 500

4-5 bed, 2 baths/shower, kitchen, utility, cloakroom

200 litres

300 - 500

4-6 bed, 3 baths/shower, kitchen, utility, cloakroom

300 litres

500 or 2x500

Large, 4-5 baths/shower, kitchen, utility, cloakroom

500 litres

Not just an Unvented Cylinder

For many years the UK has relied on cold storage tanks and copper cylinders for our day-to-day hot and cold supplies. With the introduction of mains pressure cylinders or Unvented cylinders as they are commonly known we have the benefit of wholesome potable water and power shower performance to every outlet, without the need of loft tanks. This type of cylinder linked with a modern high efficiency boiler is becoming the preferred system for many, architects, heating engineers and end users. As good as Unvented cylinders are, It is true to say that they will only be as good as the main supply that feeds them, for both pressure and flow rate, and with pressures in certain areas of the UK being reduced, and the installation of multi-bathroom dwellings, customers are demanding a system that meets their individual requirements. So more than ever it is essential to choose a system that can meet this demand. We have all suffered from showers or taps losing pressure and flow rates when other taps are turned on, Now you don't have to.

Unrivalled Performance

G.A.H (Heating Products) Ltd has developed the Dualstream system utilising the technology of an accumulator, with a Stainless steel unvented cylinder. The accumulator has a controlled butyl diaphragm that stores cold mains water at mains pressure (Like a modern day cold tank). When a tap or shower is turned on the accumulator enhances the main supply and helps maintain the pressure to all hot and cold outlets regardless of the flow rate on the incoming main supply. There is an air charge in the top of the accumulator to help force the water from the vessel into the hot and cold supplies. Enabling more than one outlet to be run at the same time maintaining pressures whilst giving greater flow rates at taps, showers and baths. Making the system ideal for properties with poor mains supplies or multi-bathroom outlets.

High Flow

The accumulator is the driving force behind the system, feeding both hot and cold supplies it must be sized correctly. More than one accumulator can be linked together for greater volume and demand. The accumulators have been designed to increase flow rates to mains fed systems and help to maintain pressures and stop pressure fluctuations on the main supply. Very simple to install with outstanding performance the Dualstream system really is the ultimate unvented package and has many benefits over traditional systems and other unvented cylinders.


Why choose a Dualstream system?

  • No cistern in the loft - no risk of water stagnation, Legionella and frost damage
  • Greater plumbing designs, uses less pipe-work, saving time and money
  • Wholesome water to all cold taps and balanced hot and cold water supplies
  • Dualstream utilises one of the slimmest and highest volume yielding unvented cylinders on the market
  • Will provide a substantial increase in water volume, to both hot and cold-water outlets, with-in the building
  • Will work at very low flow rates (9 l/mm) 1 Bar (min Water Board supply requirements)
  • Sized correctly the system will fill any number of baths simultaneously and ideal for multi-bathroom dwellings
  • True 'power shower' performance without the need of pumps
  • Overcomes problems associated with low mains pressure or inadequate flow rates
  • Efficient insulation, low power consumption. All unvented cylinders are insulated with high density CFC free insulation.
  • Can replace the need for high maintenance noisy break tanks and booster pump sets
  • Accumulators and cylinders can be linked together for greater demands, for the larger properties, small hotels and leisure and sports clubs
  • Indirect Models from 125 - 500 litres (heated from a boiler source)
  • Direct Models from 125 - 500 litres (heated from electric immersion)
  • Accumulator models from 100 - 500 litres
  • Twin coil cylinders available on request
  • Immersion heater upgrades available
  • Unvented stainless steel cylinders up to 300 litres with 25 year warranty
  • All electrical components are covered by 2 year warranty
  • Accumulators have longest industry warranty at 5 years 

    Dualstream is protected by Patent No GB 2349908 this protection applies to the use of any accumulator with any mains fed appliance (example:- Unvented Cylinder, Combination Boiler, Electric Shower) and the application of its use subject to permission being obtained from G.A.H (Heating Products) Limited. WRAS Certificate No 0109003.