Commercial?
You'll find significant savings on labor (one of your highest costs) by going straight dwc. The 'sterilization' times are reduced to a quick scrub and rinse of the res. Infrastructure costs will be significantly less with DWC, simple tubs vs. what rdwc requires. Running airpumps, instead of large water pumps, is a large savings on electricity and start up costs.
DWC is truly the lazy man's hydro for smashing results. :)
Have you read "Ask lucas" before? The reason I ask is because you mentioned using an add-back reservoir for 'stable pH.' In my experience, a full and cyclic pH swing grows vastly cleaner and higher quality cannabis. The old overgrow FAQ (and a lot of misinformed people) talk about using an add-back reservoir for pH stability, when in reality you want a full and healthy swing to be present. I remember a quote from Lucas where he strongly advises to use only plain R/O water for add-backs and is wondering where the "pH stable" junk came from.
Keep up the good work!
Douglas
lol, I guess I'm already a commercial grower, just not a legal one.
While I agree that cleaning up a bunch of DWC buckets may be less time consuming, I don't find cleaning these RDWC systems to be a burden. I drain, fill with tap water, add a couple cups of bleach and let it run for 24 hours. Scrub, drain, refill with tap water, circulate a few hours, then drain. Ready for the next grow.
The cost of running a water pump is pretty insignificant. A 500 gph mag drive pulling 50 amps costs less than $4 a month at my 11 cent per kilowatt rate. I didn't run the numbers on air pumps but I doubt they would even cost that much. I suspect both add up to less than 2% of my monthly electrical costs. Granted, overall startup costs can be high, mine are around $15k, but that was fully recovered on the second 8 plant grow. (I started with 1 system and added the second after my 3rd grow.) Having run these systems for a couple years now I wouldn't purchase another turn key system, but would build it myself. That's what I did for my veg room. A two tote, 8 plant RDWC system that cost less than $500 to build.
The biggest issue I see with running a series of DWC totes is water chilling. I run a 1/10 hp chiller on each system. Trying to cool 16 individual totes would be hard to manage. How are dealing with this?
I still have pH swings but they aren't as severe or as dramatic. I generally run my top off at about half strength of my system. I start my pH at around 5.6 and it slowly rises to around 6.0 over about 10 days. I then readjust. By the time it goes through 2 cycles it's time for a system change. I did try running straight RO but found the pH rose too quickly and the nutrients were depleted a lot faster. This might be preferable in DWC where system changes are routinely done weekly, but adding feed to the top off seems to work better when the system is only being changed ever 3 weeks.