Water Tanks, Cisterns & Pumps for Caribbean Homes
In many Caribbean homes a water tank is not an emergency accessory; it is part of the plumbing system. The useful questions are not “Should I buy a 600-gallon or 1,000-gallon tank?” but: how much water does this household actually use, how many days of reserve are needed, how much rain can the roof capture and how will pressure be maintained when the public supply is off?
Calculator 1: storage for interruptions
Calculator 2: what can your roof collect?
One millimetre of rain falling on one square metre of roof equals one litre of water before losses. The capture factor accounts for first-flush diversion, splash, gutter loss and imperfect collection.
A good domestic arrangement
Collection
Clean roof → gutter → leaf screen → first-flush device → covered tank or cistern.
Storage
Opaque or covered storage, screened openings and overflow routed away from the foundation.
Delivery
Gravity from a header tank or a pump and pressure-tank system sized to household flow and pressure needs.
First flush is not decoration
GWP-Caribbean's rainwater-harvesting resources explain that the first runoff can carry dust, leaves and animal droppings from the roof. A first-flush device diverts that initial dirty water before cleaner runoff enters storage. Tank openings also need screening so stored water does not become a mosquito-breeding site.
Header tank or pressure pump?
| System | Advantage | Limit |
|---|---|---|
| Elevated or header tank | Gravity can provide water when power is off and reduces pump cycling. | Structure must safely carry a very large water load; public-supply pressure may not refill a high tank directly. |
| Ground-level tank + pressure pump | Easy filling and strong controlled pressure. | No pressure during power failure unless the pump has backup power or another gravity reserve. |
| Cistern + small header tank | Large low storage with a smaller elevated gravity reserve. | More components and controls. |
Design the tank into the site before the house is finished
- Leave access for tank replacement, cleaning and valves.
- Put the pump where it is protected from flooding and rain but can be serviced.
- Route overflow away from the foundation and neighbouring property.
- Provide isolation valves so the public supply, tank and pump can be serviced separately.
- Decide whether collected rainwater is for garden, toilets and washing or for potable use. Drinking water needs appropriate treatment and local public-health guidance.
- If hurricanes are possible, secure exposed tanks, covers, pipes and small pump enclosures against wind and debris.