dwc - what if you dont change your res water?

Discussion in 'Hydroponic Growing' started by iamblayz, May 14, 2011.

  1. got a small dwc pc grow going, and with my dyna-gro nutes my ph stays stable enough that i dont have to adjust it throughout the week, i just add ph adjusted water to it as the res gets low

    question is what problems will i run into from not dumping the old water and replacing it with brand new water? and would it matter if i let the res get close to empty before mixing in new water?
  2. You will run into problems, algae, shit like that. You need to not only empty your rez but also clean it out and then add new water. If your rez is wicked small it shouldnt be to much of a pain to clean out...?
  3. nutrient imbalances will start to occur. Your plants use different nutrients in different amounts and they use some in higher or lower proportions. So if you just add more nutes to the old water, the proportion of elements to each other will be all jacked up....among other problems

    Just think of it like this: What if you didnt' change your underwear every day? LOL that would start to feel very uncomfortable...changing your britches every day is equivalent to changing your plants nutrient solution every week or 2.
  4. ^good way to put it.. Noone likes dirty undies.. ;P
  5. #5 doinYoda, May 14, 2011
    Last edited by a moderator: May 14, 2011
    Algae occurs when light is getting into the res, as long as your res is light proof - no algae ;)

    Nutrient deficiencies / toxicity generally occur when PH is not in check, has nothing to do with not changing the res, unless of course the grower has over-fertilized, etc...which leads to issues.

    Have had several runs without changing the water / cleaning the res during a grow and no issues :cool: Change the water and clean the res between runs. Whether or not to change out the water during a grow, seems to be grower preference. Unless there's a problem, its not a 'have to', IME/IMO of course.

    It's perfectly fine to top off with PH balanced water, and nutes when needed. As long as your top off's are frequent and you don't allow the res to completely dry up, there shouldn't be an issue, IMO.

    Best of luck to you with your grow :smoke:
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  6. thanks for the reponses

    @anton yea its small so its not really that big of an issue to dump it, was more just curious

    @aggie the difference between underwear and nutrients is that we dont consume underwear as opposed to plants which do absorb the water and nutrients, so its not that its not being changed, the old just isnt being dumped out to give it 100% fresh start, but the old water is either absorbed by plants or diluted by the new water thats coming in

    @yoda appreciate it man, i was thinking something along those lines, no light getting into my res and my ph is steady enough that i can go 2 or 3 days without checking it and it still sits in about the same place, dont know if this is a benefit of dyna-gro being a 2 part system instead of a 3 part system or i'm just lucky but it definitely makes life easier
  7. I'm currently running 2 of Budslinger's RDWC setups and have only done one flush/clean when I switched to flower and my girls are very happy in week 3 now. I'm pretty sure somewhere in Budslingers sticky he says the same as yoda that he only cleans between crops.
  8. I also only clean everything between cycles with no issues. If your ressy is small I dont see how the water can go stale...
  9. #9 aggiegardener, May 17, 2011
    Last edited by a moderator: May 17, 2011
    Here is what I have to say:
    you have a nutrient solution in your reservoir and your plant is taking up water and nutrients. As this is happening, your plants are not taking up the same elemental nutrients at the same rate or same proportion as other elemental nutrients.
    For example: during certain parts of a plant's development, it may uptake more NO3- and less H2PO4- So, the solution will have a marked decrease in 1 anion while not much decrease of another anion. There will be many more proportional differences in the uptake of different ions because plants don't always need nutrients in the exact concentrations that is in the solution and imbalances in the nutrient solution will occur because the chemistry is changing over time....pH changes for one. Plants can adapt very well to all types of elemental proportions in the solution they are growing in but if left alone for too long, there will eventually be a point when the proportions become so un-balanced that certain concentrations of nutrients will be in the toxicity level.

    I believe that this would happen if you never completely dumped your reservoir out and just kept topping off with water and adding more nutrients. Certain nutrients will keep building up (not being used as fast as the others) as you add more of your 2 part or 3 part stock solutions every 2 weeks and eventually, there probably will reach a point where a particular nutrient is at toxic levels....most likely a micronutrient like copper or molybdenum. Also, there are root exudate that are building in the water that will affect the ppm or possible microbial growth.

    I think that it is just safer to completely change the reservoir out and add fresh water and nutrients every 2 weeks. That will stop a lot of potential problems from happening.
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  10. #10 Kaiser Bob, May 17, 2011
    Last edited by a moderator: Mar 15, 2016
    You did read OP is doing a pc grow right? His res doesnt hold but a few days of water I bet.
  11. Ya, i read that. and I think a smaller scale, more chances for a little thing like the wrong kind of nutrient build up could happen just as easy.
    A suggestion: what if you put some sort of drain valve that can be turned on and off really easy and just drain it in a plastic jug every week or 2. shut the drain and add water with nutrients and the proper pH back into the reservoir....it would take 10 min every 2 weeks......I dunno.....just my thoughts :smoking:

  12. I understand what you are saying, but this is why the grower should be using a nutrient profile suited to the uptake rates of mj. this is why many people try to target rosenthal's 100-100-200 ratio. A balanced nutrient solution should have the various nutrients mixed in close to the correct proportions. A larger res will obviously increase the life of the res just as a smaller res decreases the life because of nutrient buildups. I would never run a single bucket for a whole grow with only top offs for this reason, but an rdwc with a decent size res i consistently run the whole grow without dumping.

    Regardless, I agree with your advice for OP since a pc grow is going to hold so little water anyway
  13. @aggie it already only takes 10 minutes to dump it, its not really an issue of time, if it took an hour and was needed to be done i'd do it, i'm not tryna argue against it because i'm lazy and want an excuse not to do it, its just from what i've heard and seen from multiple growers(on multiple forums) is that it doesn't need to be done, the plants may take nutrients at different rates but if your nutes have the right proportions then everything should stay in balance, one thing that can indicate this is little to no ph fluctuation, so far whatever i set my ph at it stays there with no visible change

    sure its possible to run into problems by not changing the res water but it very possible to go without changing the water and not have any problems, it seems to be about the ability to dial it in, it is definitely safer to dump the res but i'd say not needed
  14. #14 AntonROUGH, May 17, 2011
    Last edited by a moderator: Mar 15, 2016
    You woumd have ph fluctuation weither you changed out your rez every week or not.. Lots of hydro growers need to adjust there ph twice a day..
  15. no i would not have ph fluctuation, i am currently growing with hydro and my ph does not fluctuate(no more than .3 or .4) and i've found numerous grows from others using dynagro who also have very little to no ph fluctuation, i'd run out of water before my ph moved enough for it to be an issue and that's after 3 or 4 days, and when i add more water i simply ph it to whatever i needs to be, and doesn't need anymore adjustments, it stays steady

    just cause lots of hydro growers need to adjust their ph often doesn't mean all hydro growers do, i'm far from an experienced grower so i can't say why but the opinions of other more experienced growers points toward the 3 part systems the vast majority of people use being the base of these major ph fluctuations
  16. What size rez are you using and how many plants?....
  17. dont know what size rez, when i first filled it with water the sticker inside started peeling so i removed it and as soon as i was finished i realized i probably should have noted what size it was

    two plants, 1 one week older than the other

    Attached Files:

  18. Yea your rez is tiny.. Lots of people who run 40 or 50 gallon rez's with over 20 plants will see ph fluctuation. Your rez is def under 10 gallons i bet. Nice plants nevertheless

  19. Too funny; those plants are just so healthy, and lazy, and overgrowing their area. Howd' things turn out?
  20. I have not changed the water or checked the ph a single time in the last 4 grows. The plants have not had a single problem. Green, bushy, healthy, dank buds every time.

    5 gal bubble buckets, general hydro nutes, distilled water from walmart. I add nutes and raise the light when needed, thats it.

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