I realize this may be a stupid Question - I am trying to get a full understanding of nutrients for hydro and many of the instructions I am coming across talk about the Res Size, or the amount of water in the Reservoir.. I realize that in most/some cases we are talking about the Res for an Ebb & Flow type system, but when it comes to RDWC or Undercurrent, we have a Controller Bucket and a Res bucket. So when you are supposed to do a water change after adding back the amount of water equal to the amount of the Res,, Are we talking about the amount of water in the ENTIRE SYSTEM, or literally just the reservoir?
More than likely the entire system. Some people use the amount to make it easier to measure out nutrients. When talking about refilling, you need more water than the size of your reservoir. 18 gallons won't work with an 18 gallon reservoir and 6 five gallon buckets hooked to it. Although, there will be some times where they are referring to just the reservoir size. This seems common when someone is describing their setup.
I use ebb n flow and when the water gets low I drain everything out and rinse the res out to get all the trace elements out. It makes it way easier to control the amount of nutes your adding to your water.
to answer your question specifically we would need to know what system you have and how to define Res... but yes like your thinking.... typically people use the Res to only hold water in a Rdwc... this auto tops the water and keep the level constant to avoid the manual topping each day... with ebb and flows this creates a problem.. the easiest way i've found is to have the float on a ball valve to slow down the amount of water to a trickle, so when the water is passing the float during the flood it does not just over fill the whole system all that being said... I have a friend of mine who uses the res to hold more nutrients... so its soup in the Rdwc and soup in the res... I cant even fathom how he does not nuke the plants... his concentrations go so high his PH meter cannot read it... and I get calls asking why his PH is falling, hhahahahahah... I tell him to thin the soup and he never listens... but you cant argue with results... so everyone does things differently
Thanks for the responses everyone.. Yea, I figured if we are talking about reservoirs we are talking about TOTAL WATER VOLUME, so If I have a Controller Bucket and 4 Buckets attached to it, my Total volume is 15 gallons. I have a reservoir connected to top off, and that is 5 gallons. When I read something like the Lucas Formula that states to replenish the Res with Fresh Water until you have Replaced the Total amount in the Res, I am pretty sure they are talking about the total system and not just the Reservoir (in my case). Now that RDWC and Undercurrent systems are popping up more and more, the old verbiage can be a little confusing for a nubee! Nutes are on the way, and getting clones anytime now, so I am pumped!!