Well water treatment in Co. Cavan

Private wells in Co. Cavan

Cavan has fewer homes on public mains than almost anywhere in Ireland. Only 47.0% of households are on public mains, the second lowest share in the State. The 2022 Census counted 6,151 homes on a private well or other private supply, 21.4% of the county and the fourth highest share of 30 county and city areas, plus 8,620 on public and private group water schemes, 30.0% of homes. Private supplies are most common around Ballyjamesduff (29.5%) and Bailieborough-Cootehill (24.7%), with Cavan-Belturbet at 10.6%.

A household well is classed as an exempted supply, so no one monitors it for you. Every system we fit in Cavan starts from a lab report.

What's usually in a Cavan well

Bacteria

This is the big one. When the Geological Survey of Ireland (GSI) examined Cavan supply sources, mostly council and group scheme boreholes, E. coli or faecal coliforms showed up in at least one raw sample at 19 of 30 (63%). The worst results were in areas the GSI rates as extremely or highly vulnerable, where contamination reaches groundwater most easily. Ammonium was over the limit in 10 of 33 samples, which suggests farmyard dirty water, landspreading or septic tanks reaching almost a third of the wells examined. See bacteria in well water.

Iron and manganese

Manganese was over the drinking water limit in 13 of 30 GSI results and iron in 11 of 39. The GSI says raised levels would not be unusual in central and south-east Cavan, because of minerals in the bedrock, and lists both as natural issues in the sandstone and shaly limestone. Watch for orange staining and black specks.

Hard water over the limestone

The hilly east of the county is mostly older sandstone, siltstone and shale, while limestone covers the centre and north-west. Hardness is a limestone problem here: in the impure limestones of south Cavan, part of the Inny area, the GSI gives hard to very hard water, typically 380 to 450 mg/L, partly worked out from similar rock elsewhere.

Rotten eggs, sulphate and corrosion

The GSI also flags hydrogen sulphide in the shaly limestones, the cause of a rotten-egg smell. Near Kingscourt the gypsum gives calcium sulphate water, and Swanlinbar has magnesium sulphate water and old sulphur spa wells. Where the subsoil is thin over sandstone, mudstone, granite or volcanic rock, the GSI assessed corrosive water as an issue too.

What we usually fit in Cavan

Bacteria turn up often enough here that UV is likely to be on the list. In 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 where the report shows corrosive water, usually over thin soil on sandstone or mudstone.
3. Iron and manganese filter, with catalytic carbon where there's a smell, ahead of any softener so it doesn't foul.
4. Water softener on the limestone, where the water is hard.
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, which also brings sulphate down.

On mains or a group scheme and only bothered by limescale? See our water softener page for Co. Cavan instead.

The well grant in Cavan

Cavan County Council's Water Services, at 17 Farnham Street, Cavan, runs the well grant. One rule to know: all water sampling must be done by an independent laboratory accredited for every parameter tested, except odour and taste. So have an accredited lab take the sample, send us the report for an itemised quote, and check the current terms with the council before any work starts. We'll tell you which tests to order: iron, manganese, hardness, pH, nitrate, E. coli and coliforms at the very least. More in our well grant guide.