2 Pieces 3/4 Inch PVC Bulkhead Fitting for Water Barrel, Water Tank, Rain Barrels,NPT3/4 female thread(1 inch I.D.) PVC

Another alternatively you can use is a hose timer with a low bulkhead so it can completely gravity drain every 4 days. These are cheap as well and maybe a bit more accessible for the tech impaired who don’t want to deal with arduino. Either using the same filling mechanism or the ole fashioned way- waiting for rain Their AA batteries last over a year in my experience. Bucket $3 Home Depot Lowe’s etc Bulkhead -$4-5 https://a.co/d/06oqSvlu Timer - $15 https://a.co/d/0iZQZnwO