Environmental Public Health Division

Chlorination Procedure for Small Wells

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Harris County Public Health & Environmental Services (HCPHES) requires proper chlorination procedures for sterilization on all water systems that have recently been constructed or repaired, and on systems that have been flooded or exposed in any other way to contamination.  It is especially important for water supplies that have been shown to contain coliform organisms by a laboratory analysis to be properly chlorinated.  

The well should be treated in the following manner: 

·        Locate the wellhead and remove the access plug or bolt and pour one quart of bleach (Clorox, Purex, etc.) per 100 feet of well depth into the well.  Avoid using bleaches with scents or other additives.   If the well depth is unknown use one gallon of bleach.

·        After the bleach has been added, run water from an outside hose into the well casing until you smell chlorine coming from the hose.

·        Turn on all cold water faucets inside and outside the house and allow the water to run until the chlorine odor is detected. 

·        The chlorinated water should then be allowed to remain in the well and distribution system for at least six (6) hours, preferably overnight.

·        After letting the water sit in the lines the well and piping system should then be flushed out.  Start by opening an outside faucet and flush until the bleach odor disappears and continue with all other faucets.  Do not drain this highly chlorinated water into the septic system.

·        After all the chlorinated water has been flushed out of the system then a water sample should be taken in a sterilized sample bottle obtained from a laboratory and returned to the laboratory for bacteriological analysis.  (See instructions for taking bacteriological samples.) 

In case of gross contamination, the chlorination procedure may have to be repeated several times before a laboratory report indicating “Coliform Organisms Not Found” is returned.  A report with “Coliform Organisms Not Found” indicates the well is free of sewage contamination and/or disease producing organisms. 

Note:  If the pump is of the jet type that has a packer inside the well casing, it will be necessary to remove the packer to introduce the chlorine solution below the packer. 

For further information call: 

HCPHES Environmental Public Health : (713)439-6260