Is a consent to discharge needed for a house that was built before the old Water Act came into force, ie, before 1973 ?
Yes. Any discharge to underground stratum or to a waterway requires the consent of the Department under the terms of Article 9 of the Water (NI) Order 1999, which replaced Sections 7 & 8 of the Water Act (NI) 1972.
Is this not applying the legislation restrospectively?
No. It would only be so if the Department was seeking to consent a discharge which had already ceased. It is a legal requirement for all current discharges to the underground stratum, or to a waterway, to be consented under the Water Order before the discharge commences. This also applies to longstanding discharges which were not previously consented under the Water Act, irrespective of the commencement date.