How big should your water tank be?

About 20 litres a day covers the basics, and no more than that. The World Health Organization says 20 litres is often sufficient for drinking, cooking, food hygiene, handwashing and face washing, "but not other hygiene practices". The Sphere emergency minimum it cites is 15 litres; hydration alone is 5.3.

The Office of Disaster Preparedness and Emergency Management (ODPEM) asks for one gallon a person a day in storm stores, about 4.5 litres imperial or 3.8 litres US, our sum.

None of these allows for flushing, bathing or laundry. We found no Jamaican figure for whole-house use in a lock-off.

Read your National Water Commission (NWC) meter on two mornings a week apart, in a normal week, and divide the difference by seven. Your monthly bill gives the same answer more roughly, as long as it was a real reading and not an estimate.

Check the unit first, because NWC prices metered water both per 1,000 litres and per 1,000 imperial gallons.

As an example only, not an average, take 14,000 litres on one bill, the top of NWC's lowest price band. Over 30 days that is about 467 litres a day, our sum. Our bill stack shows where to find the figure.

From about 5 days at normal use to several weeks on hard rationing. These are our sums for a full tank, with 467 litres a day as the example household and 80 litres a day as four people on WHO's 20 litres.

The rationed column leaves out flushing and bathing, so your real figure falls somewhere between. Compare it with your longest recent lock-off.

A recommended minimum of 3,150 litres (700 gallons) in a home. That comes from the Rainwater Harvesting Planning Guideline of October 2023.

We could not confirm it is law. The Gleaner reported in 2023 that the minister said no to a harvesting law and that guidelines "will be gazetted". A Gleaner editorial in August 2026 doubted that this ever happened. We also found no tank requirement with a figure in the Kingston and St Andrew building checklist.

So treat 700 gallons as a good target, not a legal duty, and ask your municipal corporation if you are building or adding on. Roof collection has its own rules on our rainwater stack.

The Jamaica Observer reported in September 2026 that one St Andrew maker sells plastic tanks from 200 to 2,500 gallons, and that 650-gallon and 1,000-gallon tanks are its two biggest sellers. That is one firm's sales, not a national figure, and the report does not say which gallon it means.

By our sums, a 650 falls under the guideline's 3,150 litres whichever gallon it is, and a 1,000 clears it either way.

The documents we read give no dated tank price, so we quote none. Get prices in J$ with the date written on them.

Yes. A 1,000-gallon tank holds 761 litres less if the gallon is US, and a 650 holds 494 litres less, our sums. One imperial gallon is 4.546 litres; one US gallon is 3.785.

Official Jamaican papers use both. The 2023 guideline writes "1,000 litres (220 gallons)", which is imperial, while the Ministry of Health and Wellness has used a "US Gallon" for bleach. Ask the seller for the capacity in litres and get it on the receipt.

Two is often the better buy if you have the room. You can clean one while the other keeps the house going, and a split or a dirty tank does not cost you everything. Two imperial 650s hold 5,910 litres against 4,546 for one imperial 1,000, about 30% more, our sum.

The cost is more fittings. Ask the plumber for a valve on each tank so either can be shut off alone, and remember two tanks mean two lids and more openings to screen against mosquitoes.

If one tank holds roof water and the house also has utility supply, the 2023 guideline calls for separate or dual plumbing.

Weight, money and stale water. A full imperial 1,000 gallons is 4,546 kg of water alone, tank not counted, which is why where it stands matters as much as its size. A very large tank in a small household also turns over slowly, so water sits longer.

For the money side, the National Housing Trust's SMART Energy Loan runs "up to $2.5 million", and its rainwater line includes "tanks and pumps". It is for contributors living in a home they own. The page is undated and gives the rate only as "concessional", so ask for current terms.

Treat it as backup, and keep drinking water in clean containers as well. ODPEM's booklet asks for one gallon a person a day, with a 2-week supply at home and 3 days for evacuation. For four people, two weeks is 56 gallons, or about 255 litres imperial and 212 litres US, our sums. Back in 2010 ODPEM's head asked for at least seven days, so the booklet is the larger target.

That is a small share of any tank above, but a tank can be damaged or flooded in a storm, and containers indoors are safer. Our hurricane stack covers the rest.