Hydrogen sulphide is a chemical produced by certain types of bacteria that can grow in well water. While the bacteria and the hydrogen sulphide itself are not usually harmful at low levels, this chemical will impart an offensive rotten egg odour to the water. As well, hydrogen sulphide may tarnish fittings and stain laundry. One method to neutralise hydrogen sulphide is to perform a chlorine shock of the well, which is quickly accomplished using household bleach.
Store a sufficient quantity of water for the next day's use.
Determine an entry point through which to add chlorine to your well. This may require excavation of the well or you may have an air line leading from the well that can be used.
Disconnect or bypass any filters or other water treatment units attached to the source of well water.
Measure out a suitable quantity of bleach. For a 4-inch diameter well, use approximately one litre of bleach for every fifty feet of depth. Multiply this volume by a factor of 2 for a 5-inch diameter well and by a factor of 3 to 3.5 for a 6-inch diameter well.
Pour the bleach into the well, using the air line if necessary.
If the well was excavated, attach a garden hose to an external tap faucet and recirculate the water by turning the faucet on and placing the hose exit so the water runs back into the well. This step can be omitted if the well was not excavated and there is no opening to return water.
Go around the house and open each faucet (external and internal to the house) and run toilets, appliances, etc. until an odour of chlorine is noticeable for that particular faucet or item. Then quickly stop the flow of water by turning off the faucet or item.
Do not allow any further flow from the well for at least 8 hours, preferably 24 hours.
Attach a garden hose to an external faucet and turn the water on. Allow the water to run for 2 to 3 hours or until the smell of chlorine is gone. Ensure the water does not drain into a waterway such as a river or lake or into vegetation that you don't want damaged (such as a garden).
Turn on the various faucets and appliances (one at a time) and allow them to run until there is no longer a chlorine smell coming from the water.
If an air line is used to introduce bleach to the well, flush this line out with clean water after the addition. A slight smell and taste of chlorine may be noticeable for a few days afterwards. This chlorination may be required once a year or more often depending on the characteristics of a particular well. This treatment can also be helpful in controlling bacterial contamination and build up of metals such as iron.
Do not drink the well water until the final flushing step is complete. Minimise the degree to which the chlorinated water from flushing is allowed to enter a septic tank. This process may create a brownish sediment in the water which will eventually flush out. However, the sediment may clog items such as faucet aeration screens and jet pumps.