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Service & support


At no charge, we send you and your company the requested quantity of brochures.
To order brochures: Contact OSO Head office.

Visits from our Sales Managers

Our Sales managers regularly visit existing and potential customers.
To arrange for a visit: Contact OSO Head office.

Product and installation training

Product and installation training classes held at our Hotwater Academy in Hokksund, Norway.
To arrange for a training course: Contact OSO Head office.

Water quality

For most people in the Western world, clean water is a matter of course. But even if the water looks clear and tastes good, there is always a certain content of different minerals which – when the levels are sufficiently high - may cause problems in various water installations. In Europe, water coming from municipal water supplies is usually quality assured and treated so that the content of minerals is at an acceptable level.

This is not the case when it comes to most private water supplies, and the most challenging water qualities are to be found amongst these. As a result, OSO Hotwater is not able to guarantee products installed in private water supplies.



The OSO stainless steel inner vessel is guaranteed against material defect or manufacturing faults for a period of 10 years from the date of purchase. All other parts including, but not limited to, factory fitted electric heaters (damage caused by lime scale excluded), expansion vessel, thermostats and valves are guaranteed against material defects or manufacturing faults for 2 years from the date of purchase. In the event of a replacement component being required OSO Hotwater will supply such part(s) free of charge and freight paid, on condition that the defective component is delivered, freight paid to OSO Hotwater within 2 weeks of written notice being given to OSO Hotwater of the defect. Such replacement parts shall be guaranteed under the terms of this guarantee to the unexpired period of the aforementioned 2 year period. This warranty is conditional upon the OSO cylinder being installed in compliance with the OSO Installation & Maintenance Instructions, all current legislation, codes of practice and regulations governing the installation of unvented hot water cylinders in force at the date of installation and provided that:

  • The water quality shall be in accordance with European Council Directive 98/83 EC, or revised version at the date of installation, and is not fed with water from a private supply.
    Chloride content: Max. 250 mg/l
    Sulphate content: Max. 250 mg/l
    Combination Chloride/sulphate: Max. 250 mg/l (in total)
  • The OSO cylinder is filled with water before turning the electricity supply on to the heater elements. If the newly fitted water heater is not in regular use then it must be flushed through with fresh water for at least 15 minutes. Open at least one hot water tap once per week, during a period of at least 4 weeks.
  • The OSO unvented cylinder has not been modified in any way other than by OSO Hotwater and is only used for the storage of potable water.
  • No factory fitted parts have been removed for unauthorised repair or replacement.
  • Defects caused by frost, excess pressure, salt dehardner process, transient voltage, lightning strikes or incorrect installation, repair or use, are not covered by this warranty.
  • Evidence of the purchase date and the date of supply must be available upon request.

To validate the warranty the user must complete and return the warranty card supplied accompanied by proof of purchase within 60 days of purchase. Evidence of the purchase date and the date of supply / installation must be submitted.

This guarantee does not confer any rights other than those expressly set out above and does not cover any claims for consequential loss or damage. This guarantee is offered as an extra benefit and does not affect your statutory rights as a consumer.