Rdwc question

Got a question for you guys every week I make up about 113 L of nutrients since the girls have gotten bigger they’re drinking at least 30 to 50 L of water a week and that depletes half the reservoir what I’m thinking is my reservoir has a float valve where I can connect a top of tank if I was to make up enough nutrients that would last 2 to 3 weeks would the nutrients in the top up tank stay good for that long?

My experience (only two grows) is that chemicals in nutes start to precipitate out after a few days. If you’re diligent about stirring the top off tank or if you drop in a little “mixer”, that will get them off the bottom of the tank but you’re still going to have nutes from which some chemicals have fallen out of suspension.

Bigger picture? Plants don’t take up the chemicals in nutes at the same percentage rate. Strains differ, plants take up nutes at different rates depending on the stage of growth, and nute uptake varies as pH varies. All in all, lots of things going on “beneath the waves” to which we’re not privy. With “low turnover” res, you might be able to push it out to three weeks but you’ve got thirsty plants so I’d be surprised if things weren’t out of whack pretty quickly.

What kinds of TDS and pH readings are you seeing as the res ages?

the readings (e.c) in the reservoir generally stay the same or go down p.h generally goes up a couple points but if it goes to far out of whack I use 1.5 pH down to get it back to the recommendations

Sounds like you’re doing things right. Predictability is the key and, with your pH rising gradually until you have to drop it with Down, that’s pretty much textbook.

One thing that I saw mentioned at Percy’s Grow Room, the source for “Son of Wonder Chart” , below, is that the optimal pH in flower is 6.0 vs 5.8 in veg. That’s the only source I’ve read that states that so hat’s off to https://percysgrowroom.com.

Hope this stuff helps even though it looks like things are dialed in. I just checked the cannabis laws in the UK. Ugh. Keep your head down!

I’ve attached a couple of resources from my wanderings around the internet. I refer to them as “WonderChart” and “Son of WonderChart”.


Looks like I can’t upload a text file. The following text is the text of the footnotes for WonderChart:
""Note 1.
When pumping air into a nutrient solution in order to add Dissolved Oxygen, not only oxygen is present, CO2 is also pumped in. If you live near a busy road, this may be higher than normal, so you may get a dropping ph quite often. I have noticed most of the growers who suffer from a falling ph in DWC tend to live in large cities. This may not be a link but it could be.
When CO2 is added to water, it makes it more acidic. This is the precise process which causes acid rain, pollution from power stations etc pouring CO2 into the air, this mixes with the water vapor in clouds causing acid rain.

Note 2.
Most people assume that with a rising EC, it is the plants way of saying, I don’t want more food, here, have some back.
What is actually happening is this.
Plants roots take in water/nutrients through a process called Osmosis. Think of the roots as having their own “internal EC”.
The osmosis process will always try to balance out the EC’s, taking from the higher side of the barrier and giving to the lower part.
So if the EC of the nutrient solution is higher than the “internal EC”, then food & water will flow from the solution to the roots, this is the normal process.
If however, the EC of the solution is lower than the “internal EC”, then the balancing will work the other way and nutrition will be leeched from the roots to the solution.
A res change or increase in EC should resolve depending on the other factors such as ph and water levels.

Note 3.
Nutrients flow around a well hydrated plant much more effectively and faster than one which isn’t as well hydrated.
How can growers use this?
By feeding at lower levels, the plant needs to take on more water in order to get the nutrition it requires.
So by feeding at moderate levels, this forces the plant to drink more.
By drinking more, it is better hydrated, because it is better hydrated, it needs more food, making it eat more.
So feed at moderate levels rather than overly aggressive levels.
The method of pushing the EC until you see signs of nute burn is damaging to the plants and although many growers use this method, I am not a fan though your plants are not mine!

If you disagree with stuff in this post, please PM me. I do not want this thread to end up as a big debate or argument. I am hoping people take it as an honest attempt to help those suffering issues in DWC. The info in this post is my opinion. Before taking any corrective action based on this post, please double check."

http://www.thctalk.com/cannabis-forum/archive/index.php/t-86654.html
"

I agree with everything you said and I also use those charts you linked above