Hours : Mon - Fri - 8:00am to 4:30pm
   (573) 748-5541

Water Testing

Water Testing

   This information provided by the Environmental Public Health Specialist with the New Madrid County Health Department. 

Water Supply and Sewage Disposal in Emergency Situations 

     Procedures and guidelines are given to ensure safe water for drinking and sanitary disposal of wastewater when frequently used facilities are not available.  When using chemical disinfection with water for drinking, there are two sanitizers that can be used – one is bleach the other iodine.  To date no information has been found where quaternary ammonia could be used.   

Drinking Water Disinfection  

     Household bleach is the most common sanitizer with chlorine providing the disinfecting by killing bacteria and viruses.  Most bleach is 5.25% - 6.00% (use only unscented).  At most all you want for drinking is 2.0 parts per million (ppm) free available chlorine so you add a small amount of bleach to a gallon of water.  2 liter soda bottles are preferred over used milk jugs (if possible make sure all the residual milk is rinsed out).  An eyedropper or medicine dropper is the easiest way to add 8 drops per gallon to get 2.0 ppm (with soda bottles use 4 drops).  With chlorine the easiest way to check the residual is to use a swimming pool test kit.  This will give you total chlorine.  Ideally what you want to know is the free available chlorine for this is what can disinfect water – total chlorine shows you free available chlorine as well as what is not available for disinfecting.  If present allow particles to settle out then add bleach and check for chlorine.  In most instances, total chlorine will be relatively close to the free available level.  For drinking water you want a chlorine residual of 0.5 parts per million (ppm) to 2.0 ppm (ppm = milliliter per liter (ml/L) = milligram per liter (mg/L) for this is the level typically found in public water supplies.

     Useful equivalent measurements are also provided.  For example, you can mix one eighth (1/8) teaspoon of bleach to one gallon of water to get 1.0 – 2.0 ppm chlorine.  With 10 gallons use two teaspoons (3 teaspoons = 1 tablespoon).  Larger quantities of water can also be disinfected for drinking.  With 1,000 gallons use 5 to 6 tablespoons (2.5 to 3 ounces) of bleach (2 tablespoons = 1 ounce, 8 tablespoons = 1/2 cup, 8 ounces = 1 cup).  Some basic math can also be used to determine quantity of bleach to add for gallons not listed here and proportions are useful for this.  For example, 750 gallons:


 1,000 gallons  x  750 gallons  

 5 tablespoons             x

 1,000X    =     3,750

 X    =    3.75 or 3 ¾ tablespoons of bleach for 750 gallons. 

     To describe what was done – we know that 5 tablespoons bleach in 1,000 gallons of water gives about 1.0 – 2.0 ppm.  What we want to know is how much bleach to add to 750 gallons of water so x is what we are looking for.  Cross multiply and divide solving for x – this gives you 3 ¾ tablespoons of bleach to add to 750 gallons of water. 


     Iodine from a medicine chest or first aid kit can also be used to disinfect water for drinking.  Add 5 drops of 2 % United States Pharmacopoeia (U.S.P.) tincture of iodine to a quart of water.  Four quarts are in one gallon so add 20 drops to 1 gallon.     

     Another way to disinfect water for drinking is to boil it for at least 3 minutes. 


     Disposal of wastewater or sewage is the concern when normal treatment of wastes is not available.  Ideally you want to treat the waste to remove the bacteria and viruses present.  Agricultural lime can be spread on waste, burial in shallow trenches (not greater than 30 inches deep if possible), transport to a public sewage system if available, use of bleach or other sanitizers (quaternary ammonia, iodine) to kill bacteria and viruses, spreading of waste on to the ground in places that are well-exposed to sunlight – these are all ways to reduce the public health threat.