You have the bucket test right. Would be interesting to know the actual leak rate. Ignore the fact some loss is due to evaporation and start to record the level and time as accurately as you can. On your 12,000 gallon pool if you assume a 48" water depth that relates to 250 gallons per inch. I thik my rate was around 40-50 gallons per hour but I'd have to look at records to know for sure. That was easy to spot with the dye.
Al
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