How many GPHs would you need to water a Ebb and Flow flood tray that is about 2 ft by 4 ft? The hose would have to rise about 2-2.5 ft in order to reach the flood tray. I was looking at a 396 GPH pump, but that seems like overkill. Also how long do you have your watering system on for? (I know most people run it three times a day, but for how long? 15 minutes?) Thanks, DD
What size water pump? (1 cubic foot = 7.48 US gallons) I think 396gph is way too much pump for your application. first thing we need to figure out is how much water you have to move into the flood tray. you said your tray is 2'x4'x?" Im going to guess that your tray is 10" tall your overflow water line is somewhere between 6" and 8". Im going to use 6" because it will be easier for everyone to understand. 2'x4'x6" = 4cu ft x 7.5 = 30 gallons. Lets say you want it to take about 5 mins to fully fill up. so it would look like this 30/5 = 6(gallons / min) x 60 min = 360 Gallons per hour. so I would say with whatever grow medium you are using and whatever # of pots you have in your flood tray You could use a pump from a 250gph to about 350gph. If you have a harbor freight in town go get a pump and start trying them out, If I was you I would start on the low side with a 250gph pump. The last thing you want to do is get home set it all up and realize your over-flow drain doesn't drain fast enough. Oh yeah and 2.5ft of lift is not that much to worry about. As for time 15 mins. is fine if your using Hydroton or something similar. and set it for 4 times per day then adjust as needed you might be about to flood it 6 times a day without seeing over-watering symptoms. If your using a STG or Rockwool medium I would only set your watering to 2 times per day. Sorry I cant really give you an exact figure for amount of time to water cause I don't know anything about your plants or medium.