Imperial from Hernando writes
We recommend that you apply 4 oz of Invade Drain Gel in each drain opening when they are not in use. You should refrain from running water down the drain after application so the product has time to be effective in breaking up the organic matter in the drain. We also suggest appling 2-3 squirts of Gentrol IGR Aerosol after the drain gel to impede the insects reproductive cycle. Please let us know if you need anything else. How to Get Rid of Drain Flies Article
Answer last updated on: 06/14/2015