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Choosing a water storage tank for your home

By the Plain Prepper editors. Updated 2026-10-14.

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Quick answer

Start from the government rule of thumb: Ready.gov says to store at least one gallon per person per day, and FEMA suggests at least a two-week supply. That is 56 gallons for a family of four. Small food-grade containers cover that. Larger above ground tanks hold a month or more. Norwesco's vertical water tanks run from 120 to 10,000 gallons, use resins that meet FDA specifications for potable water, and come in black or green to limit light and algae. Self-filled water should be replaced every six months.

How much water to store

Ready.gov says to store at least one gallon per person per day for drinking and sanitation, and notes that needs can double in very hot weather. FEMA's food and water guide recommends at least a two-week supply for each family member.

People	3 days	14 days	30 days
1	3 gal	14 gal	30 gal
2	6 gal	28 gal	60 gal
4	12 gal	56 gal	120 gal
6	18 gal	84 gal	180 gal

Ready.gov adds that children, nursing mothers and sick people may need more.

Containers vs tanks

• Bottled water. FEMA calls commercially bottled water the safest and most reliable supply. Keep it sealed and watch the use-by date.
• Food-grade containers. FEMA recommends buying food-grade water storage containers. If you reuse bottles, it says to use two-liter soda bottles, never milk or juice jugs, since milk protein and fruit sugars cannot be fully removed. It also advises against glass, which is heavy and breakable.
• Above ground tanks. For a month or more, a single tank is easier to fill, drain and refresh than dozens of jugs. Norwesco's vertical tanks start at 120 gallons.

What makes a tank safe for drinking water

Norwesco's water tank flyer lists the features to look for in any potable tank:

• Resins that meet FDA specifications for safe storage of potable water, and NSF approval where applicable.
• A black or green color that limits light, which reduces algae growth.
• One-piece polyethylene construction.
• Self-vented lids and built-in gallon markings.

Norwesco also rates these tanks at 8 pounds per gallon and states they are for water storage only, never chemicals or fertilizer. A tank that once held anything else does not belong in your drinking water plan.

Tank sizes and footprints

Capacity	Diameter	Height	Family of four at 1 gal/person/day
120 gal	38 in	31 in	30 days
220 gal	42 in	44 in	55 days
305 gal	46 in	50 in	76 days
500 gal	48 in	73 in	125 days
1,000 gal	64 in	80 in	250 days

Sizes are from Norwesco's flyer. Most of its tanks come with a 2 inch drain and a 1.5 inch top fitting installed. Check how a tank will fit through your gate or garage door before you order it.

Where to put it

• Cool and dark. FEMA and Ready.gov both say to store water in a cool, dark place. Norwesco's opaque black or green walls limit light outdoors.
• A solid, level base. At Norwesco's 8 pound-per-gallon rating, a full 305 gallon tank weighs at least 2,440 pounds. Set it on a pad that can carry that without settling.
• Tie it down. Norwesco builds tie-down slots into its tanks. Use them.
• Plan the outlet. A drain near the bottom with a valve lets you fill buckets by gravity when the pump has no power.

Filling and refreshing

1. Clean the container or tank with dish soap and water and rinse it well.
2. FEMA says to sanitize bottles with 1 teaspoon of unscented household chlorine bleach per quart of water, swished over every surface, then rinsed out.
3. Fill from a chlorinated city supply, which FEMA says needs nothing added. For well water or other untreated sources, FEMA says to add two drops of unscented bleach per gallon.
4. Close it tightly, write the fill date on it and store it cool and dark.
5. Replace self-filled water every six months, as FEMA and Ready.gov advise.

FEMA also names water already in your home, such as the water heater and pipes, as a safe backup source.

What to look for when you buy

Questions people ask

How much water should I store for an emergency?

Ready.gov says at least one gallon per person per day. FEMA recommends at least a two-week supply, which is 56 gallons for a family of four.

What kind of tank is safe for drinking water?

One made for potable water. Norwesco's tanks use resins that meet FDA specifications for potable water, carry NSF approval where applicable and are rated for water only.

How often should stored water be replaced?

FEMA and Ready.gov say to replace water you bottle yourself every six months. Keep commercial bottled water sealed and follow its use-by date.

Can I reuse milk jugs for water storage?

No. FEMA says milk protein and fruit sugars cannot be fully removed from those jugs and can feed bacteria. Use food-grade containers or two-liter soda bottles.

Sources

• Water, Ready.gov
• Food and Water in an Emergency, FEMA and American Red Cross
• Water Tanks flyer (vertical water tanks), Norwesco

Sources checked 2026-10-14.