Well water treatment in Co. Offaly

Private wells in Co. Offaly

The 2022 Census counted 3,750 Offaly households on a private well or other private source, 13.1% of the county and 11,245 people, up from 3,620 homes in 2016. That puts Offaly 12th of the 30 county and city areas. Offaly also leans on group water schemes far more than the country as a whole: 4,999 homes, 17.4%, against 7.7% nationally, and private group scheme homes have climbed from 1,430 in 2016 to 2,608. Public mains serve 68.2%.

A household well is exempt from the drinking water regulations, so testing and treating it is down to you. The EPA advises a test at least once a year.

What's usually in an Offaly well

The Geological Survey of Ireland (GSI) names nitrate and faecal bacteria as the main contaminants from human activity in Offaly, and iron and hydrogen sulphide as the main natural problems. Most of its figures come from council and group scheme sources, not household wells.

Hard to very hard water

Limestone bedrock and limestone boulder clay cover most of the county, so the GSI rates Offaly groundwater generally hard (251 to 350 mg/L) to very hard (over 350 mg/L). Springs in the Geashill area measured 288 to 457 mg/L, Coolagarry near Walsh Island was over 350, and around Clara the GSI expects 380 to 450 mg/L. Expect scale on kettles, showers and immersion elements.

Iron and a rotten-egg smell

High iron and hydrogen sulphide have both been reported in private wells in the Calp limestone around Ballycommon and Portarlington. The GSI notes the smell often comes with iron and is common. Iron is likely at times in all the muddy limestones and in places around Slieve Bloom, and around Clara iron and manganese fluctuate above the EU limits. Expect orange staining, black specks and a rotten-egg smell from the hot tap.

Bacteria

None of Offaly is rated low vulnerability by the GSI: 11% is extremely vulnerable and 55% highly vulnerable, which means pollution from the surface can reach groundwater easily. Its 1999 report found isolated faecal bacteria in treated water at the Banagher, Clonbullogue, Mountbolus, Rahan, Rhode, Shinrone and Walsh Island public supply wells and in the majority of group schemes. See our guide to bacteria in well water.

Nitrate

In 1998 the larger supplies averaged 19 to 24 mg/L of nitrate, but the GSI rated three sources, Ballaghassan (since disused), Clerhane and Guilfoyles, as regularly exceeding 50 mg/L. More in our nitrates guide.

What we usually fit in Offaly

Most Offaly wells need some or all of this line, in this order, with any stage the report doesn't call for left out:

1. Sediment filter to protect everything after it.
2. Iron and manganese filter, which takes the rotten-egg smell too, and has to come before the softener or the metals foul it.
3. Water softener sized for very hard water.
4. UV disinfection if the report shows E. coli or coliforms, fitted last on the main line so the water reaching the lamp is clear.
5. Reverse osmosis at the kitchen tap, which also takes nitrate out of the water you drink and cook with.

On mains water and only bothered by limescale? See our water softener page for Co. Offaly instead.

The well grant in Offaly

Offaly County Council's Environment and Water Services Section runs the Individual Well Grant from Áras an Chontae, Charleville Road, Tullamore (057 935 7416, envandwater@offalycoco.ie), and publishes its own terms and conditions for it. A house connected to Uisce Éireann or a group water scheme doesn't qualify, and nor does one that has had a water supply grant in the past seven years. Bring the council your lab report and our itemised quote. Our guide to the private well grant covers the rest.