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Fresh water system

Fresh water system. Matter to be decided:. Potable water Wash water Pressure in the system: usually 10 to 40 psi 69 to 275 kPa 0.69 to 2.75 bar. Pressure set. is a unit consists of:

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Fresh water system

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  1. Fresh water system

  2. Matter to be decided: • Potable water • Wash water Pressure in the system: usually 10 to 40 psi 69 to 275 kPa 0.69 to 2.75 bar

  3. Pressure set is a unit consists of: • Pump (usually displacement type) • Accumulator tank • Pressure switches: high and low pressure

  4. Accumulator tank

  5. Accumulator tank benefits: • Absorbs the pulsations in supply from the pump (works as air vessel) • Extends pump life • Reduces battery drain

  6. Choice of the pressure set • Decide how many outlets you require • What flow is required from each outlet (from manufacturer specification) • Estimate how many outlets will be opened simultaneously • Decide your maximum normal flow requirement • Choose the pump according to that flow and the chosen pressure

  7. Carbon based water filter • Filters, freshens and cleanses stored water to give a fresh, clear, natural taste • Activated carbon removes unpleasant tastes, smells and colours, including chlorine • Removes suspended dirt, sediments and fibres • Silver impregnating inhibits bacterial growth when not in use

  8. Water heaters (Calorifiers ) • Heat Transfer – cooper coils with engine cooling water, heat accumulator • Electric Elements -The rating should not exceed 1200-1800 watts, thermostat is required • Calorifier Valves – non-return valve pressure relief valve drain tap • Insulation - polyurethane foam, some companies quote a 0.5°C loss per hour • Installation - The calorifier should be mounted on the same level as the engine cooling water source or below

  9. Diesel Hot Water Heaters

  10. Instantaneous water heater • Electrical – 6kW for shower – 3 Litres/min • LPG If the choice is LPG read installation requirements on boats. Web info: • http://www.insightmarinesurveyors.co.uk/gas.htm • http://www.gaslow.co.uk/pages/marine.htm • http:// www.yachtworks.net/propane_installations.htm

  11. Fresh water tanks Integral in mild steel, aluminium, GRP or wood vessels then the tank internal surfaces need to be coated with an epoxy based paint approved for drinking water use. Separate tanks. The tanks may be constructed from any material if internally coated. Usual practise is to use stainless steel (A1S1 316L) which, like purpose built GRP separate tanks (with GELCOT on the inside) do not require coating internally.

  12. Water consumption Add 15% to 25% margin for emergencies, excessive consumption, etc.

  13. All tanks should be supplied with the following: • (a) Filling pipe work of adequate size, • (b) Air ventilation pipe led as high above the main deck as possible, incorporating a swan neck and mesh filter, • (c) Manual sounding tube for dip stick use to check capacity of tank, • (d) Tank outlet to be of sufficient size and led from point of tank via internal pipe if necessary, • (e) Suitable fitting for remote sensing of tank levels (electric, mechanical or pneumatic), • (f) Inspection man-hole of suitable size to allow visibility and access • (g) To be appropriately baffled.

  14. Fresh water tanks location • double bottom or bilge area obviously to maintain a lower VCG and maybe divided fore and aft to supply the accommodation in the ends of the vessel

  15. Some rules and considerations 1. Install the pump as close as possible to the water supply tank, consistent with a dry, ventilated & accessible location. correct incorrect

  16. Some rules and considerations 2. Keep suction pipework as short and straight as possible with minimum suction lift. Use rigid pipe or reinforced hose that will not deform or collapse under suction conditions. Ensure that all connections are airtight. correct incorrect

  17. Some rules and considerations 3. The internal diameter of the suction pipe should be at least as large as the nominal bore of the pump ports. correct incorrect

  18. Some rules and considerations 4. Fit a suction line strainer between supply tank and pump. Make sure that it is accessible, and remember to inspect it periodically. correct incorrect

  19. Some rules and considerations 5. Avoid transparent / translucent pipework, which is susceptible to algal growth./ correct incorrect

  20. Some rules and considerations 6. Use discharge pipework of adequate size — 13mm (1/2”) internal diameter in small systems. In larger vessels, use 13mm (1/2” branches to taps etc. from a 19mm (3/4”) or 25mm (1”) main pipe running the length of the vessel. correct incorrect

  21. Some rules and considerations 7. Check that pump cut-out pressure is suited to all other system components, e.g. calorifier. correct incorrect

  22. Some rules and considerations 8. Always fit an accumulator tank — the larger the better. correct incorrect

  23. Some rules and considerations 9. After refilling an empty supply tank, open one outlet before switching on the pump. This allows the pump to re prime itself rapidly.. correct incorrect

  24. Design details to be considered when developing a freshwater system are as follows: • Bolted connections should not be made through the shell of potable water tanks, • Pumps, manifolds (filling, transfer, and suction), and gauges should be grouped, • Potable water services should be grouped to keep the number of branches from the main to a minimum, Service branch sizes should be based on the number of fixtures installed. • All risers exposed to the weather should have means for draining to prevent freezing,

  25. Potable water piping should not be run through bilges. • All branch connection to the main freshwater system should be provided - with stop valve, • A non-return valve should be installed in the supply to water heater, to prevent hot water from backing up in the cold water piping, • Gauge glasses should have guards, or be otherwise protected against accidental breakage

  26. In addition • Additional requirements regarding freshwater systems are contained in the regulations of the Public Health authority involved. A thorough understanding of these regulations should be obtained before undertaking the design of a freshwater system for commercial and passenger vessels. • In these cases fresh water supplied for drinking and culinary purposes must meet purity standard specified by the Department of Transport. Water produced from most evaporator/distillers will not meet these standards and must be treated to ensure it is biologically pure and neutral or slightly alkaline.

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