A grant may be available to assist in carrying out remediation, repair or upgrading works to, or replacement of a domestic waste water treatment system (DWWTS) that serves a house. 
Grants are available under the following schemes, however there are restrictions on eligibility under each scheme.
1.    National Inspection Plan – on foot of a Septic Tank Inspection by Local Authority. 
2.    DWWTS in Prioritised Areas for Action 
3.    DWWTS in High Status Objective Catchment Areas
Further information is available from:
Gov.ie - Domestic waste water treatment systems (septic tanks)