Frequently Asked Questions

Disinfection of a well

In the event that a sample of drinking water from a domestic well, submitted for analysis by the homeowner is unsatisfactory, you will be required to disinfect your well and resample to ensure it is safe to drink.  Please see below for advice on disinfecting a well.  Bottles and laboratory analysis request forms and advice can be obtained from the Public Analyst in your area.

You will need:

(1)        900gm (2 lbs) of Chloride of Lime (containing 35% available chlorine); or

(2)        450gm (1 lb) of High Test Hypochlorite (50 – 70% chlorine); or

(3)        Laundry bleach Sodium Hypochlorite 3 – 5% of available chlorine: 9 litres (2 gals of 3%, or 5 litres (1 gal) of 5% strength.

For (1) or (2), dissolve in 25 litres (5 gals) of water. Mix thoroughly.

For (3), make up a solution to 25 litres (5 gals) of water to obtain 10ppm chlorine. Mix thoroughly.

Pour half the solution into the well, start up the pump, and open all the taps until the water from each tap has a distinct smell of chlorine. Then stop the pump and add the rest of the solution. Allow to stand for 12 – 24 hours or overnight, then pump to waste until the smell of chlorine disappears.

A resample will be necessary to ensure the disinfection process was satisfactory.  In the event that a sample is still unsatisfactory, you may need to seek the advice of a water hydrologist.

Further information may also be available from the Geographical Survey of Ireland – www.gsi.ie