Food & Water Precautions


Following strict food and water precautions while traveling in a developing country will decrease your risk of illness and disease. If food is thoroughly cooked and served hot, you can generally consider it safe. As a rule, eat hot food hot, and cold food cold.


Only water that has been adequately disinfected (boiled, filtered and/or chemically treated) will protect you from viral and bacterial waterborne diseases. If boiled at sea level, water should be brought to a rolling boil for at least one minute and cooled. Tap water may be safe in hotels in large cities frequented by travelers, but when in doubt, drink treated water. In areas where water and sanitation are questionable, the following should be considered:

Water Treatment

For potable water stored in tanks, it is essential that chlorine be added to inhibit bacteria and algae growth (see below). Potable water includes tap water from known safe water sources as well as rainwater. Water made from water makers is generally safe to drink, although it may taste flat. Consider adding lime or lemon juice or a pinch of ascorbic acid to improve the taste. Remember that supplementing shore water with water made from a water maker will mix non-potable and potable water, and that the entire tank should then be treated.

For Potable Water From a Known Safe Water Source

Use the following chart for adding household bleach (5% sodium hypochlorite) to your potable water, as it will inhibit bacteria and algae growth in your tanks. It is recommended that you use a syringe that has increments in metric measurements, milliliters (mls). Note that mls are the same as ccís (cubic centimeters). Syringes can be purchased at most pharmacies. Beware that many countries are now stocking "ultra bleach" usually 7-7.5% hypochlorite. Try to read the label and try to stick with plain 5% sodium hypochlorite, which is standard household bleach. As it may be difficult to maintain a constant level of chlorine (3-5ppm), a simple swimming pool test kit may be useful. Iodine is not recommended because of health risks associated with the frequent and long-term use of iodine.

For Non Potable Water

To kill or remove harmful bacteria, viruses and organisms that may cause disease, water must be disinfected. The following method combines filtration to remove cyst organisms (e.g. cryptosporidium) and chlorination to kill the Giardia , bacteria and viruses.

Use the following chart in for adding household bleach (5% sodium hypochlorite) to your tank water. This will remove remaining viruses and inhibit bacteria and algae growth.

Bleach Dosing For Water Tanks

Sodium Hypochlorite 5%, water measured in liters


1 ounce = 30 cc 3.84 liter = 1 gallon
1 tablesoon = 15 cc 1 teaspoon = 5 cc
1 cc = 20 gtts (drops) 1 liter = 0.2604 gallon


Water should be clear and allowed to stand for 30 minutes after application of bleach, prior to drinking. Add double the amount of bleach for cloudy or colored water. After treatment, water should have a slight chlorine odor. If not, repeat the dosage and allow treated water to stand for an additional 15 minutes. Maintain the recommended level of chlorine (3-5ppm) by checking the chlorine levels every two weeks, using a simple swimming pool test kit.

To use the chart, calculate the total number of liters or gallons you wish to treat. Then, read across to the amount in mlís of bleach you need to add to your tank.

Liters of Water ml or cc Drops
1 0.1 2
2 0.2 4
3 0.3 6
4 0.4 8
5 0.5 10
6 0.6 13
7 0.7 15
8 0.8 17
9 0.9 19
10 1.0 21
20 2.1 42
30 3.1 63
40 4.2 83
50 5.2 104
60 6.3 125
70 7.3 146
80 8.3 167
90 9.4 188
100 10.4 208
200 20.8 417
300 31.3 625
400 41.7 833

On Going Tank Maintenance

It is a good idea to sanitize your water tanks at least twice a year by mixing 1-teaspoon of liquid dish washing detergent and 1/8 cup of household bleach. After the solution is dissolved, pour it into your empty water tank(s). Add 5 gallons of warm water; rock the boat (if you can) to distribute the solution before opening each tap on board, including those in showers, until solution appears at the faucets. This is difficult with baffled tanks and large boats. Let the solution remain in the tank and lines for at least an hour to ensure good disinfecting. Open all taps and allow the solution to completely run out. Follow this by at least two full rinses of the tank. This, of course, is done when you have plentiful potable water supplies (Practical Sailor, December 1998, p.5).

Personal Tips

I am in charge of water disinfection on our boat. I use a watermaker and add household bleach to our tanks prior to filling them or making water to inhibit bacteria and algae growth. To add bleach to each of our tanks, I first pour a small amount of bleach into a container and then draw up the necessary amount with a syringe. On the water tank next to the inspection port I have marked the amount of chlorine bleach (with an indelible marker) needed to disinfect a full tank of water. Thus, I never have to look up the amount of bleach I need to add to a full tank of water. If you do not have inspection ports, you will need to draw up the amount of bleach in your syringe and inject it into the fill ports. Chase it down with about a gallon of water to flush the bleach into the tank itself.

Jan Loomis is a registered nurse and paramedic who is currently cruising with her husband, Geoff Wickes, aboard their Valiant 40, Meridian Passage. She holds a faculty appointment at Oregon Health & Science University where she works in the emergency department and was formerly the coordinator of the Travel Medicine Clinic. She has sailed the Tasman Sea, Caribbean, Pacific Northwest, Kingdom of Tonga, Australia, and, most recently, Mexico and the Sea of Cortez.

James Bryan is a board certified emergency physician at the Portland Veteran's Affairs Medical Center and Oregon Health & Science University. He holds a PhD in Pharmacology and is the lead editor of the EMRA Guide to Antibiotic Use in the Emergency Department. He is an active member of the Wilderness Medical Society and has participated in wilderness search and rescue for over twenty-five years.

The Healthy Cruiserís Handbook, Prevention and Treatment Medical Resource Guide, is available from: Seaworthy Publications, 215 S. Park Street, Suite #1, Port Washington, WI 53074, (262) 268-9250,

by Janette Loomis, RN, BS,
Meridian Passage
and James H. Bryan, MD, PhD
from: The Healthy Cruiserís Handbook, Prevention and Treatment Medical Resource Guide.
ISBN# 0-9721077-0-3.