MANDERSON Well Drilling

Disinfecting Your Well For Coliform Bacteria.




Step 1


Remove the well cap and dump 1 gallon of bleach into your well for every 50 gallons of water in the water system, including the well.  3 - 5 gallons for the average well on PEI.  Use any bleach that has 5.25% Sodium Hypochlorite (Regular Javex, unscented).  3 - 5 gallons looks like overkill, but part of this is because the bleach already lost much of its chlorine value on the store shelf. 

Note: In a 5" well, every foot of water in the well is approx. 1 gallon. 


Step 2


Hook a hose to the outside tap and run the hose down the well for at least 10 minutes before going to step 3.  Leave this hose running down the well until the end of step 4.


Step 3


Turn off water heater and run hot water tap in the bath tub until you can smell the bleach then shut it off.  This might take up to 10 minutes.  The tub faucet runs at about 4 gallons per minute and the hot water tank might hold 40 gallons or more.


Step 4


Now go to every hot & cold tap in the house.  Run each one separately until you can smell the bleach then shut it off.  Do not forget the dishwasher, washing machine, toilets, and shower heads.  If there is any question about whether or not you can smell the bleach, just keep dumping more bleach in the well until the doubt is gone.


Step 5


Turn off the hose and remove it from the well and put the cap back on.  Leave the bleach in the system for a minimum of 12 hours.  Use a minimum amount of water during this period.  It's okay to flush the toilet a few times.


Step 6


Flushing out the bleach.  Run the outside tap wide open.  Hook a hose to the hot water outlet behind the washing machine.  Run the hose outside through a window or door.  Then let both hot & cold hoses run until the smell of bleach is gone.



Disinfecting for Iron Bacteria


Follow same instructions as above, only double the amount of bleach and the leave in time after disinfection. For example, 2 gallons of bleach for every 50 Gallons of water & leave bleach in for 24 hrs. When flushing out the bleach in Step 6, run the cold water for 24 hrs.


Pointers for Disinfecting


The above method works in most cases, but it does not do a very good job of disinfecting the aquifer just beyond the well. Also, if the well is deep, (over 200 feet), the bleach might not make its way to the bottom.


To do it right, chlorinated water must be injected into the well & distributed evenly throughout the well via a hose.


Also, in older wells some bacteria is protected by hiding in their own Bio Film that is attached to the sides of the well. To fix this, the pump must be removed and the well brushed to break up the bio film. The debree should then be removed from the well. Pump the well for 24 hrs min. before adding chlorine.




Cities & towns that rely on ponds or lakes for water have no choice but to chlorinate. If not, they risk getting E-coli from Beaver, Racoon, or Duck droppings.


For places that use wells to supply municipal water. If the wells are working the way they should, there is no need for chlorine except for the times when a well is being worked on or the system is being flushed.


Chlorine has been used for about 100 years with great results. But should we be using it to treat clean well water with a good history? Will the bacteria ever become immune to the chlorine? Some bacteria are already resistant, but chlorine still kills the vast majority.


Penicillin became available in 1943 and in 1947 the first penicillin resistant bacteria were reported. DDT was discovered in 1939 and by 1990 there were more than 500 species that were resistant to at least one pesticide.






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