Well water treatment in Co. Roscommon

Private wells in Co. Roscommon

The 2022 Census counted 2,267 Roscommon households on a private well or other private supply, 8.7% of the county. Far more, 4,555 homes, are on a public or private group scheme, between 16.5% and 18.5% of households in every district. Private supplies are most common in the Athlone district on the Roscommon side of the Shannon (10.9%) and around Boyle (10.2%), and least common around Roscommon town (5.5%).

Most supplies in Roscommon draw on groundwater: by council figures from 1999, 12 of 15 public schemes and 47 of 56 group schemes drew on it. Nobody monitors a household well for you, though. It's an exempted supply, so testing and treating it is down to the owner, and every system we fit in Roscommon starts with a lab report.

What's usually in a Roscommon well

Hard to very hard water

About 60% of Roscommon sits on one clean, heavily karstified limestone, and the Geological Survey of Ireland (GSI) classes 67% of the county as a karst aquifer, where water flows through open channels in the rock. Across 28 public and group schemes on that limestone, the water ranged from hard (250 to 350 mg/L) to very hard (over 350 mg/L), often with limescale problems. In south Roscommon it's typically 380 to 450 mg/L.

Bacteria

The GSI sampled raw, untreated water at 51 supply sources and found faecal coliforms at 40 of them (78%), including all 28 springs. There's no county figure for household wells, but they draw on the same ground. Brosna and Castlestrange group schemes failed the E. coli standard in 2023 and 2024, and Castlestrange failed again in 2025. The karst crosses county lines too: tracer tests near Ballinlough traced water underground from Coolcam to Meeltraun in Mayo. See bacteria in well water.

Iron and manganese

These come mainly from the sandstone and shaly limestone. The council's rural water monitoring in 2000 found nearly half of sources over the EU iron limit and 166 of 1,098 samples over the manganese limit. You see it as orange or brown staining, black specks and tinged laundry.

Rotten-egg smell and corrosive water

The GSI also names hydrogen sulphide, the rotten-egg smell, in the shaly limestone, and corrosive water from sandstone, mudstone and volcanic rock under thin soil. Those rocks form the hills: Kilronan Mountain, the Curlew Mountains and Slieve Bawn.

What we usually fit in Roscommon

Most Roscommon wells are on hard limestone and need the line below, in this order, with stages left out if the report doesn't call for them:

1. Sediment filter to protect everything after it.
2. pH correction, only if the report shows corrosive water, which is possible on the hills.
3. Iron and manganese filter, which also deals with the rotten-egg smell and stops iron fouling the softener.
4. Water softener sized for hard to very hard water.
5. UV disinfection if the report shows E. coli or coliforms, fitted last on the main line so the water reaching the lamp is clear.
6. Reverse osmosis at the kitchen tap for drinking water, if you want it.

On mains water around Athlone and only bothered by limescale? Our Athlone water softener page covers Monksland and the Roscommon side of the town.

The well grant in Roscommon

Roscommon County Council's Water Services Section runs the grant for improving a private water supply to a house (waterservices@roscommoncoco.ie), and gives filtration or UV treatment as examples of what it covers. Check the council's conditions before any work starts, then bring it your lab report and our itemised quote. We'll tell you which tests to ask the lab for: iron, manganese, hardness, pH, nitrate, E. coli and coliforms at the very least.