Private wells affected by Storm Emma should be disinfected

If your well has been affected by Storm Emma you should make sure it is properly disinfected before using it for drinking water.

This is the advice the Environmental Protection Agency (EPA) has given to private well owners around the country.

Such procedures should be carried out once the flooding has subsided, the agency has said. The EPA has also published advice and guidance for households using private wells.

This includes information on:
  • Protecting your private well water;
  • Testing and treating your well water;
  • Concerns and complaints;
  • Further guidance and frequently asked questions.

This information includes a ‘Protect Your Well Assessment’ app and a short animation explaining how to protect your private well.

The EPA has also published an “Advice Note on Restoring Public Water Supplies Following Flooding” which should be used by water suppliers, such as Irish Water and Group Water Schemes operators, if supplies have been affected by flooding.

Disinfecting your well after flooding

This method is for the disinfection of a well water supply, water storage tank, water carrying pipe work and hot and cold-water cylinders. Approximately 1,100 litres of water will be used.

Add 5L of a 1% w/v solution of sodium hypochlorite to 25L of water.

According to the agency, any one of the following products may be used diluted in 25L of water: 2.5L of Milton fluid (or 50 tablets) or similar products with 2% w/v sodium hypochlorite; OR 0.5L of Sterichlor or similar products with 10/11% sodium hypochlorite.

Disinfection products sold for use on the farm will be acceptable for use in disinfecting wells. However, it is important to seek advice about their use and it is advisable to always use the products in about 25L of water.

The procedure:
  • Pour half of the solution into the well;
  • Turn on the drinking water tap in the kitchen and let the water run until there is a distinct smell of chlorine from the water. Then turn off the tap;
  • Turn on all other taps and let the water run until there is a distinct smell of chlorine from the water. Then turn off the taps;
  • Pour the other half of the solution into the well. Turn off the well pump and ensure that the well is covered properly. Allow to stand overnight or for at least eight hours;
  • After at least eight hours reconnect the pump. Turn on all taps and let the water run until the smell of chlorine is gone. Turn off all taps;
  • Arrange for the water to be tested.

The EPA stressed that this method is only suitable as a once-off shock disinfecting procedure and cannot replace a proper treatment system if one’s water supply needs continuous disinfection.

The agency also cautioned that if a filter, or any other type of water treatment, plays any part of one’s water system, the supplier should be consulted before following this procedure.

Heavily chlorinated water may affect the filter or the chlorine may be absorbed by the filter, rendering the procedure ineffective, the EPA warned.