Freshwater System Pumps

[SailNet]

Freshwater system pumps provide the luxury of having water at sinks and showers by simply opening a tap or by pumping a hand or foot lever.

TYPES 
There are two main types of freshwater system pumps, electric and manual.

Electric water-system pumps can provide water on demand by two methods:

• Manual-demand pumps use an electric switch located on the faucet for control and must be used with faucets that have an integral switch. These pumps don’t produce water instantly or much pressure.
  
• Automatic pumps have built-in pressure switches to turn them on and off. They accept standard fixtures and newer, sealed pressure switches are increasingly reliable and easily replaced if they should fail. 
  
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  	Electric Diaphragm Pump

  Diaphragm pumps are the most commonly used freshwater system pumps found in most boats. There are two basic types:
  
  
  
  • Single-chamber diaphragm pumps, often with an open motor and belt driven piston.
    
  • Multiple-chamber diaphragm pumps, sometimes referred to as "wobble-plate" pumps.  These models are quieter and more efficient than their older counterparts. Multiple chambers boost efficiency and provide a steady flow of water. Electric diaphragm pumps are self-priming and can operate dry for short periods of time. Newer pumps have built-in check valves and sealed switches. Some maintenance is required because of their wear on parts like check valves and diaphragms.

	Manual Piston Pump

Manual water-system pumps are used by some sailors in lieu of electric pumps, while others install them as backup units to the electric models in case the electrical system goes down.  There are several models of manual pumps. 

• Piston-style hand pumps have a very traditional look.
  
• Rotary-style pumps have check valves and are easy to install.
  
• Foot-operated diaphragm pumps free up counter space and leave both hands free.
  

TIPS

• Manufacturers' pump flow rates are based on unrestricted discharge flow and the pump motor operating at continuous full voltage. The voltage at the pump motor, the head (the discharge height the pump works against), length of hose runs, hose bends, and even the hose’s interior surface (ribbed or smooth) affect pump performance.
  
• Match the pump flow with the fixtures (faucets) on board. Restricted flow fixtures (water-conserving devices) will cause back pressure in the system causing pump cycling and excessive electric consumption if there’s too much flow. Choose a pump with less flow (GPM) but a high-pressure (PSI) rating in this case.
  
• Use high-capacity pumps with large accumulator tanks for shower and sinks. These will give you the feel of being at home.
  
• Install a shut-off valve in the input hose before the pump so that it can be disconnected for maintenance.
  
• Add a pre-filter screen to keep any dirt or debris out of the delicate pump internal parts to prolong the pump's life.

ACCESSORIES

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  Accumulator tanks reduce pump cycling caused by minor pressure variations. They also provide a more constant flow of water and store enough water to eliminate pump cycling when small amounts of water are used.

INSTALLATION
The average-skilled sailor with basic tools and some electrical skills can install a pump.

Toolbox

Manual pumps require:

• Drills and bits
  
• Bolts, nuts, and washers
  
• Screwdriver
  
• Hose rated for the use and stainless steel hose clamps

Electric pumps require:

• Tin-plated wire
  
• Connectors
  
• Soldering iron if required
  
• Wire cutter/stripper
  
• Wire ties and clips
  
• Multi-meter
  
• Additional circuit breaker for electrical system if required

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