SiteRep

How far must a septic tank be from a well in Ireland?

The EPA Code of Practice for Domestic Wastewater Treatment Systems requires a minimum separation distance of at least 30 metres between a percolation area and any well used for drinking water, and this distance can need to be greater depending on ground conditions, groundwater vulnerability and the direction of groundwater flow.

Protecting drinking water wells from contamination is one of the central concerns of the EPA's Code of Practice for Domestic Wastewater Treatment Systems (population equivalent of 10 or less). It sets a minimum separation distance of 30 metres between a percolation area and any well providing water for human consumption — whether that well is on the applicant's own site or a neighbouring property.

This 30 metre figure is a minimum, not a guarantee of safety in every case. In areas of high groundwater vulnerability, karst limestone, shallow soil over rock, or where the site characterisation shows groundwater flowing towards the well, a greater separation distance or an alternative, more robust treatment system may be required before the site is considered suitable.

Because groundwater does not respect boundary lines, the assessment must consider wells on adjoining land as well as the applicant's own, and this is a common reason rural sites near existing wells face a longer or more demanding site suitability process, or need enhanced secondary treatment rather than a traditional percolation area.

Factors that affect the required well setback

A site assessor will typically consider:

  • The location of all wells within the zone of influence, not just those on your own site
  • Groundwater vulnerability mapping (extreme, high, moderate or low)
  • Depth to bedrock and subsoil permeability
  • Direction of groundwater flow relative to the well
  • Whether the site is in a karst limestone area with rapid groundwater movement
  • Whether the well is a private drinking water source or a group water scheme intake

Where the 30 metre minimum cannot realistically be increased to a safe margin, a higher-specification secondary treatment system with tighter effluent quality standards is often the practical solution.

When to check with the council

Always disclose known wells, including a neighbour's, to the person carrying out your site characterisation, and query the requirement with the local authority's water services or planning section if a well of uncertain status lies near the proposed percolation area.

Sources

Last reviewed 20 August 2026. General information only — not legal or planning advice.

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