Of 30 septic tanks units inspected last year in Co Leitrim, 20 had advisory notices issued and 14 were ruled to be a risk to human health or the environment.
The Environmental Protection Agency released these figures as part of a review of the implementation of the National Inspection Plan for Domestic Waste Water Treatment Systems for January 1 to December 31, 2016.
Figures for Co Leitrim show that one third of those tested by Leitrim County Council under local authority inspections, failed to meet operational standards.
One of the septic tanks tested showed leakage from the system while a further 10 septic tanks had unlicensed discharge. Three units inspected by Leitrim County Council had surface ponding while two systems had proof that roof water was entering the system.
Seven of the systems failing standards had issues with operation and maintenance while 11 tanks needed de-sludging. Shockingly, a total of 14 septic tanks, nearly half of all those tested, were ruled to be a risk to human health or the environment.
The EPA has stressed homeowners need to take action to protect themselves, their families and neighbours from risks posed by septic tanks.
Nationally, half of septic tanks tested failed local authority inspection in 2016.
According to the EPA, the majority of septic tank failures are mainly due to a lack of proper operation and maintenance.
Homeowners should, say the EPA, have a proper treatment package in place where their septic tank is serviced regularly and full service records are kept.