Is changing res water in dwc really necessary?

Theoretically, if you're keeping the water clean and roots healthy, couldn't you just keep adding fresh water to the res? ...along with nutes and (hydroguard) ... maintaining desired ph and ppm.

For how much the plants drink later in their lifespan, it seems to me the water would be completely, newly cycled every week or multiple times a week anyway, just by adding so much fresh water to top off the res.

This is my first grow, and I'm just theorizing and planning for the best and easiest path. The plants seem so happy in the water they're in, and the water has no smell and the roots look fantastic. Seems I could just keep topping off and adding nutes to maintain the ppm range I'm going for.

Has anyone had success doing it this way?

Eventually you should. I have run a full 4 week veg cycle without changing the nutes. I actually compared 4 buckets with Hydroguard and 4 with UC Roots and let the rez temps stay in the high 80's - low 70's and didn't change the rez once. I topped them with RO or fresh nutes depending on their uptake. They all grew great. I'll always do it this way from now on.

But that's about the duration that I myself would go before a full changeout. The plants aren't going to take up all the nutes together at the same time. It might take up one faster than another, or one not so much at all. Eventually your rez can become completely chemically unbalanced and nutes getting locked out even though your pH and PPM look ok. Eventually you want to flush out that spent shit and start over.

That makes sense. My plants are only a bit over 3 weeks, so they aren't taking in much nutrition yet. I've changed the res once and twice on the other, but probably could have just gone the whole first month without a full res change. The ppms are only slowly dropping, so I haven't felt like i needed to add more nutes yet. But I understand about the plant using some nutrition more than others and eventually the res will have too much of something and a lot less of another. Makes sense.

I see posts where people say their dwc is empty when they check on it because the plants drank so much. That is mainly what got me questioning the necessity for full res change, since if the plant takes all the water in a few days, there wouldn't be any water left to change out anyway, and what you add to it would be a fresh res change. But in early veg stages, that's not happening yet obviously.

Yeah I can't speak to that that so much. I veg in 5 gallon buckets but move them to a big RDWC system for flowering. In peak mine probably drink about 6 or 7 gallons a week each. So much easier changing 1 rez than multiple buckets...

I'm just looking to get a modest yield, probably won't be doing anything more than single pot hydro or soil. I'd like to try soil next, just to compare. Seems it may be a bit cheaper overall doing soil. Loving the way the hydro is working though, seeing the white roots expanding into open water and the plant growing happy above. But I'm the type who prefers a set it and leave it type approach, so soil is probably forthcoming. Nice for a first grow to be more involved with the plant and tending to it, I do enjoy it.

Only time I do it is going from veg to flower. you're correct in saying they drink so freaking much that you need to replace so often there's almost No reason to switch.

Airwalker16 said:

Only time I do it is going from veg to flower. you're correct in saying they drink so freaking much that you need to replace so often there's almost No reason to switch.

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How long do you veg for? I was planning on beginning flower when they're a bit less than a foot. I'd like to keep them on the smaller size. One is 6 inches already now

Depends on ho many plants your rez is feeding and how big they are

BadlyDrawnBoy said:

How long do you veg for? I was planning on beginning flower when they're a bit less than a foot. I'd like to keep them on the smaller size. One is 6 inches already now

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Depending on how big your grow space is , i veg d mine for about 6 weeks before i switched to flower to fill a 4x4 grow space .

I do a rez change bout every 4 weeks. And when switching to flower. I run 3 in a 18gal tote with copious amounts of great white

BadlyDrawnBoy said:

Theoretically, if you're keeping the water clean and roots healthy, couldn't you just keep adding fresh water to the res? ...along with nutes and (hydroguard) ... maintaining desired ph and ppm.

For how much the plants drink later in their lifespan, it seems to me the water would be completely, newly cycled every week or multiple times a week anyway, just by adding so much fresh water to top off the res.

This is my first grow, and I'm just theorizing and planning for the best and easiest path. The plants seem so happy in the water they're in, and the water has no smell and the roots look fantastic. Seems I could just keep topping off and adding nutes to maintain the ppm range I'm going for.

Has anyone had success doing it this way?

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Lots of variables

• How much water in your system? Larger volumes of water will last longer
• Water temps - higher temps can create root root and slime
• Exposure to light - light will encourage microbes to grow, creating algae and slime

I'm going to have around 80-gallons in my 4 plant RDWC. I'm going to see how the water's doing when I flip them. I'd like to go the whole grow without flushing, but I might flush when I flip.

More water has a lot of benefits

• Stays fresh longer
• More pH/nutrient buffer
• Helps keep water temps down

Not changing your water weekly or every 5 days in DWC is like buying a Ferrari and never going over 5mph!

Twerkle said:

Not changing your water weekly or every 5 days in DWC is like buying a Ferrari and never going over 5mph!

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I'm actually going to flush every other week. I've got a lot of water (50 - 60 gallons) and only 4 plants. I'll play it by ear.

JSB99 said:

I'm actually going to flush every other week. I've got a lot of water (50 - 60 gallons) and only 4 plants. I'll play it by ear.

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Trust me i know the pain of changing i got 120gallon rez of RO so i use between 300 to 400 gallons of prefiltered water a week. but water is cheap and why decrease your yield to penny pinch.

the reason we grow dwc is because we get to submerge the plant in the perfect mixture of nutes at all times. if you are not changing regularly or if you are only topping of with new nutes and water you have no idea of the contents of the rez anymore. at that point might as well do soil.

It is possible to maintain a nutrient solution for the life of the plant, but it needs a carefully balanced nutrient profile for the top off water.

Bruce Bugbee from Utah University has developed it for growing tomatoes in recirculating hydroponics..

Peace
BL

I've done DWC for 16 years and have tried changing regularly and not changing for the whole grow. I've run side-by-side tubs changing one a few times and not changing the other once with no difference in results or yields. I've settled on changing once after the stretch then just take out some of the nutes and replace with RO water to lower the ppm during later flower.

There is certainly no reason to change weekly when the plants are small and barely eating anything. You are just wasting perfectly good nutes and making more trips to the hydro store to make them richer.

This whole "gonna get different nutes off balance" is just malarkey. Never seen any deficiencies even when the nutes never got changed once. Not a great plan for a brand new grower but once you can read your plants fairly well it's easy-peasy.

I use the pH Perfect nutes and long ago retired my pH pen. I grow in single RubberMaid tubs so just have to top up, check ppm and boost nutes as needed to maintain the ppm level I want every 3 days with big plants.

Now if DWC would just cut flowering time in half like it does with veg times I'd have the best of all possible worlds.

Here's a table demonstrating the rates of removal of different elements from a recirculating solution.



Nutrients brands with a high Calcium content for example will cause issues as it accumulates in the solution due to it's slow removal.

Peace
BL

OldMedUser said:

I've done DWC for 16 years and have tried changing regularly and not changing for the whole grow. I've run side-by-side tubs changing one a few times and not changing the other once with no difference in results or yields.

This whole "gonna get different nutes off balance" is just malarkey. Never seen any deficiencies even when the nutes never got changed once.

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That's been the main reason I have kept up with res changes. Good to know there is more leniency than I thought

Strange, I just got a notification saying my post had been quoted, when it hadn't....

@OldMedUser which nutrient brands/products have you used for your runs with no nutrient changes?

Peace
BL

In my albeit limited number of dwc grows (4 now..), I've had different experiences - I think as long as you're checking the water regularly and change the res before any problem gets out of hand, you don't really need to follow a strict schedule

I've been using Lucas with GH in dwc- first with the flora series (micro+bloom) and now I'm trying the flora nova bloom for the first time.

With the flora series, I was starting to see issues with what looked like nute lockout about 2-3 weeks in. This couldve been my fault, too, from just not dialing it in - but I think I did.

With the flora nova bloom, I haven't changed out the res fully once- all I've done is a half change. My plan was to go all the way to harvest without changing the res if it can make it