Managing Your Water Supply  –  The main water supply for some buildings and homes here in the BVI is derived from both city water and cistern water. City water can be as reliable as the electricity, so having your cistern system in working order can serve as a good backup.

City water has a pressure regulator located at the main cut-off.  Without this regulator, there can be a surge of pressure that may rupture the internal plumbing in the building.  There should be a check valve located before the city meter that helps prevent pressurized cistern water from entering the city water line.  At times, this valve may fail, resulting in cistern water flowing into city water.  Privately owned brass check valves should be installed after the utility meter to further help secure any cistern water from entering city water lines.

The pressure supplied from the city water may not be enough to maintain proper pressure to the top floors of a multiple-dwelling building, especially considering that the pipelines supplying the floors are usually ½-inch PVC.  Should two tenant areas decide to use water at the same time, the reduction in pressure and volume may well be noticed.

The cistern supply should have a primary check valve installed to prevent city water from entering the cistern lines.  Shut-off valves need to be in place at all areas of concern that will allow the water to be cut off as needed.  As with city water, the pressure needed to supply proper water pressure and volume will be reduced when more than one tenant area requires water.  All multiple-dwelling buildings should have individual water pump and pressure vessels to ensure reliable pressure and volume to each tenant area.  

The location and installation of the cistern water pump is critical to maintaining safe and reliable water.  The cistern pump is a “push pump” that is standard for any cistern installation requiring a pressure vessel to maintain water pressure.  This type of pump should not be installed too  high above the cistern.  The pump is not capable of delivering adequate pressure while struggling to draw up water. In order to draw up water, a “draw pump” or “well pump” is required.  This is a specialty pump, and one that needs to be installed by a qualified plumber knowledgeable about them.

Check valves need to be installed in the supply lines to prevent water from dropping, further labouring the pump.  The pump needs to be bolted down and secured or its vibration and torque will crack the pipelines.

The supply pipeline should be located six inches from the cistern floor, run up to the highest location of the cistern before entering a dry area.  From this point, the pipeline drops down to the pump, thereby reducing the draw load of the pump.

As stated above, each tenant area or floor should have its own pump and pressure vessel.  This will prevent any loss of pressure or volume to other areas.  One pressure vessel is inadequate for the water distribution in multiple-dwelling buildings, even with large pressure vessels.  Once the pressure drops down to its low-pressure level, the pump will kick on and try to pressurize the vessel while struggling to supply several tenant areas with proper water volume and pressure.  A larger pump motor may help eliminate this problem for the most part but it is not the perfect solution.

The supply lines from the cistern to the pump motors should be no less than what the fitting requires and designed in such a way that check valves and shut-off valves are specific to the cistern requirements.

Multiple-tenant areas use up water fast—some more than others.  To monitor tenant area usage, privately owned water meters can be installed to monitor cistern water consumption for each tenant area.