• WRAS Approved

  • Independently tested and validated in accordance with BS EN 14897:2006 + A1:2007

  • BIM models available

  • Ultraviolet light intensity monitored supplied with all models as standard.

  • Preburnt lamps to 200 hours to maximise biocidal potency

  • Doped quartz sleeve to prevent the formation of O-zone and other potentially undesirable by-products.

The disinfection of water by the use of ultra violet light is a proven and well accepted method for the control of bacteria in water systems. It is commonly accepted that UV light is damaging to living tissue, the most notable example of this being the rise in skin melanomas and the advice to use high UV factor sun creams to reduce the risk to health. The HydroWELL® range of UV disinfection equipment provides an excellent and cost effective control of biological populations in water, the application of ultra violet light with HydroWELL® systems is straight forward, adding integrity and security to the process being treated.


All HydroWELL® products in the ranges Compact E, Select and Standard are fully WRAS approved, Ultra violet light is a naturally occurring light and some reaches earth every day from the sun. Ultra violet light is thus part of the natural spectrum of light and is differentiated by its wave length, measured in nano-metres. Visible light occupies the wavelength between 400 and 750nm (approximately), with the colour violet occurring around the 400nm wavelength part of the spectrum. Ultra violet light occupies the part of the spectrum adjacent to this and is found in the band 10 to 400nm (approximately). It is not visible to the human eye, though high concentrations are very damaging to the eye and exposure to it must be avoided. Thus care must be exercised whilst servicing this type of equipment, as blindness can result if the eye is exposed to this wavelength of light. Hydrotec do provide a full service capability via our fully trained service engineers. The application of UV light for the disinfection of water systems, is however more complex than this.

dna string

It is known that UV light kills bacteria by disrupting the DNA (this is the material inside of every living cell, that defines what the cell is and controls every aspect of its metabolism and survival), this is in sharp contrast to techniques such as high temperatures and chlorine dioxide which ‘burn’ the outside of the cell wall. For this technique to work successfully, the wave length of UV light that is employed must be carefully selected, this is because different wave lengths of light are absorbed in different proportions by the DNA and for this method to be successful, the UV light must be absorbed to cause the necessary disruption. Research has shown that the optimum wavelength for the destruction of biological matter occurs close to 260nm, and therefore it is important that the lamps used to provide UV light are close to this ideal value. (Ultra violet light of this wave length, falls into category ‘C’ and is thus often referred to as a UVC light or Germicidal light). The process of killing bacteria, via this technique is often referred to as ‘inactivation’.

In addition for the correct application, the exposure rate of the UV light is also important, for typical clean potable water applications, 250J/m2 is advised, where biological loads are likely to be higher, this value is normally increased to 400J/m2. All biological species require differing exposures to UV light to inactivate them, some like legionella pneumophilla, will die at relatively low exposures, other like pseudomonas, which can also cause problems, are more robust and do require a higher dose of UV light to inactivate them. The relative ‘strengths’ of these bacteria are shown in the graph below.


​Every HydroWELL® UV disinfection system also incorporates a UV photo sensor to monitor the effectiveness of the disinfection. The output of every lamp will drop with time, typically lamps last between 8,000 and 16,000 hours dependant on lamp type, after which it will require replacement. However during the operational life of the lamp, it is also possible for other factors to affect performance, such as the deposition of mineral or organic matter on the quartz tube that separates the lamp from the water. In cases where this occurs it may be necessary to remove and clean the quartz tube, between lamp replacements. The natural occurrence though of these foulants is not un-common and confirms why the UV photo sensor is vital and the reliance on lesser systems such as timer or lamp fail indictors do not guarantee the performance of the disinfection system.

To ensure that optimum results possible are gained from each HydroWELL® UV disinfection unit, Hydrotec advise that prefiltration should be considered where HydroWELL® is used, this helps to eliminate effects such as shadowing and to maintain the clarity of the quartz tube and thus reduce maintenance. It is important when utilising HydroWELL® UV disinfection systems as part of a water treatment program that full consideration be given to the correct placement of the unit in the system. The most common location for the placement of HydroWELL® is on the incoming main to a building (or after the booster set if a water storage tank is employed). This is known as ‘Gate Keeper’ technology and the unit acts as the system’s ‘sentinel’, on guard every hour of every day. It should be remembered that all water borne bacteria, undesirable or benign, will enter the system via the incoming main, and despite the water undertaker’s care and diligence it is simply not possible to deliver water across the network in total sterility, thus the job of protecting your systems starts with treatment of the incoming main. This treatment adds considerable value and security to the water handling process. It is most likely that in addition to the protection given by the UV disinfection system, that you will also employ additional protection against legionella bacteria (as advised by the Health and Safety Executive’s L8 code of practice) such as temperature regime.

Other Applications

HydroWELL® UV disinfection systems have long been used in the protection of water systems for use in buildings. However the quality and wide range of features of the unit also mean that it has found application in many other areas. Here are some of those possible:

  • Rainwater harvesting. This technology has seen considerable growth in recent years and as its use has become more widespread, so have the problems associated with it. In almost every case, harvested water will contain (or is likely to contain) pathogenic bacteria, therefore Hydrotec strongly advise treatment in every case. With suitable design, HydroWELL® can successfully be deployed on these systems.
  • Swimming pools. Widely in use in continental Europe, UV disinfection has either replaced or allowed the use of much lower chlorine levels in the pool, this has led to a greatly improved bather experience, eliminating the residual chlorine smell and sore eyes that can often result from the use of chlorine based technology.
  • Bore hole water treatment. A significant rise in the number of private bore holes has been noted, HydroWELL® can be used successfully as a primary method of bacteria control in these systems.