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MERCHANT SHIPPING NOTICE No. M.1401
Disinfection of Ships Domestic Fresh Water

Notice to Ship owners, Masters, Fishing Vessel Skippers, Shipbuilders and Repairers

l. The Merchant Shipping (Crew Accommodation) Regulations 1978 as amended and the Merchant Shipping (Crew Accommodation) (Fishing Vessels) Regulations 1975 require that all fresh water produced on board the ship shall be disinfected automatically.

  1. Merchant Shipping Notice M.1214 entitled “Recommendations to Prevent Contamination of Ships’ Fresh Water Storage and Distribution Systems” together with the “Instructions for the Guidance of Surveyors”, both issued by the Department, deal more fully with all the related recommendations and advice.
  2. At the time of issue of Merchant Shipping Notice M.1214 (June 1986) only chlorination, with its residual capability, could be recommended for use as a disinfectant in shipboard fresh water systems.
  3. However, further research work has now been undertaken in respect of the use of silver as a disinfectant. Given the results of this work, together with the historically satisfactory use of silver as a disinfectant in shipboard fresh water as well as land based systems, the Department now accepts electro-silver ionization systems for the automatic disinfecting of fresh water produced on board United Kingdom registered ships.
  4. The conditions of acceptance which are applicable to the fitting of such disinfection systems are detailed in the Annex to this Notice.

Department of Transport
Marine Directorate
London WCIV 6LP
December 1989
© Crown copyright 1989

ANNEX
ELECTROLITIC SILVER RELEASE FRESH WATER DISINFECTION SYSTEMS

The Department accepts electro-silver ionization systems for the automatic disinfecting of fresh water produced on board United Kingdom registered ships.
A summary of the conditions of acceptance which are applicable to the fitting of such disinfection systems is given below.

  1. 1. Any proposal for fitting a system on a passenger class UK registered ship is to be submitted to the Marine Directorate for individual consideration.
  2. 1. The installation of any unit supplied for ships intended for the United Kingdom registry should be undertaken in accordance with the manufacturer’s detailed instructions.
  3. 1. A set of manufacturer’s instructions covering fully the installation, operation and maintenance of the disinfection systems should be filed with the Department for record and supplied with each unit for the reference of the operators.
  4. 1. The disinfection unit is to be fitted in the fresh water system between the production unit and the storage tanks, as near to the former as is practicable and in a readily accessible position.
  5. 1. Each system is to be designed for the maximum flow rate of the fresh water production unit.
  6. 1. “Fail Safe” operation of the disinfection units is to be achieved by fitting an automatic, normally closed solenoid operated valve in the system. The valve is to be under the independent control of the electrode monitor such that the valve will close and prevent the passage of water into the storage distribution system should the unit malfunction in any way.
  7. 1. An audible visible automatic alarm should be installed connected to the “Fail Safe” control system and should give a warning of failure of power supply or any malfunction of the disinfection unit causing closure of the solenoid operated valve. The electricity supply required to operate the alarm should be independent of the supply to the disinfection unit.
  8. 1. No facility for by-passing the disinfection unit is to be fitted or provided.
  9. 1. The design setting of each unit is to be checked by the manufacturers before dispatch and is to be such as to ensure that a minimum of 0.1 ppm silver concentration will be added to the water under maximum flow conditions.
  10. 1. The fresh water storage and distribution system should be designed such that the silver contact time with the water is a minimum of four hours before use. This will ensure a maximum silver concentration of 0.08 ppm in the system. This concentration is to be checked by a competent laboratory annually.
  11. 1. Any water “conditioning” units should be installed before the disinfecting unit and before storage.
  12. 1. Spare parts not less than the manufacturer’s minimum spares list (see manufacturer’s instructions) are to be carried for each unit fitted.
  13. 1. Acceptance is based on the information supplied by the manufacturer and is subject to the system operating satisfactorily in service. The Department reserves the right to require check tests to be made at any time.