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Get extra keen discounts and beat expensive shipping costs by buying books through this site! The free delivery service applies to most established destinations worldwide. Boat water systems – living under pressure
Pressure water systems are another area where complexity has crept in to displace simplicity. Whereas a simple hand or foot pump once dispensed only cold water – subsequent heating involving a flame and a kettle – the pressure water system on a modern yacht or power boat now has hot and cold running water at the turn of a tap.
Whether a pressure water supply is a good thing or not depends on one’s priorities and is, anyway, outside the scope of this book. But to be entirely reliant on an electrical device is to leave oneself vulnerable. The prudent boat owner would be wise to retain a manual system, if only as a back-up. To avoid the waste that inevitably goes with such a lavish supply, many ocean voyagers literally pull the fuses on their pressure water pumps while at sea.
Overall, boat water systems are pretty reliable. The only mechanically complex component is the pump and long distance sailors can always carry a spare. A typical system is shown below and should be self-explanatory. But, just to run through the basics…
- The fresh water is contained in a tank (or tanks) fitted with a stopcock to allow work to be done downstream should it be necessary.
- On demand it then passes through a strainer which removes any debris that might damage the pump…
- …which is the next stage in the water’s progress. These are usually diaphragm type pumps with flow rates anywhere between 4 litres/minute to nearly 20 or so litres/minute, depending upon the water demand for a particular installation.
- Immediately beyond the pump is an ‘accumulator tank’ – effectively a pressure buffer which smooths the water flow and prevents rapid on-off cycling of the pump.
- Just beyond the accumulator the cold water supply branches off and goes to the various outlets – taps, showers, etc – in the installation. An activated carbon filter should be fitted to any outlets likely to supply drinking water.
- Meanwhile, the pressure driven water passes through a one-way valve and past an expansion tank. This is similar or identical to the accumulator but it does another job. As the name suggests, its task is to deal with the expansion in the calorifier as the water heats up. Without the expansion tank the pressure could build up sufficiently to open the calorifier’s relief valve and water would be lost.
- The calorifier is an insulated vessel containing a coil through which hot water from the engine is circulated. By simple conduction the heat is transferred to the surrounding fresh water. In addition, calorifiers often contain a mains voltage immersion element (not shown here) for use when alongside.
- From the calorifier the hot – actually very hot – water passes to a mixer valve which combines it with cold water to reduce it to an acceptable temperature.
Maintenance:
- Most of the components are non-serviceable – that’s to say if they fail they must be replaced.
- However, the strainer should be inspected periodically and cleared if necessary. This will obviously entail closing off the water supply at the stopcock.
- All activated carbon filter elements should be replaced at the beginning of every season. If left unused for any length of time, bacteria can build up inside them, with a possible threat to health.
- Even if your shore supply is known to be potable, the occasional treatment with a water purifying chemical is still advisable to inhibit any contamination in tanks or pipework. Many proprietary products are based of Sodium dichloroisocyanurate (mercifully abbreviated to NaDCC) but there are others chemicals that are used. Always use in the recommended concentration.
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Related Reading: Reverse Osmosis Water Purification
Mechanical & Electrical Pressure Water Systems - convenient but wasteful
