What's the longest time you can keep your res without topping off?

I don't change my res but for every 2-4 weeks unless I encounter a sickly plant or some other issue. But more often than not, everything coasts along just fine. Being in standalone 5 gal DWC buckets, I do have to add more water and nutes back every few days, and every day when they get to late flower and eat/drink a lot more.

Logan Burke said:

I don't change my res but for every 2-4 weeks unless I encounter a sickly plant or some other issue. But more often than not, everything coasts along just fine. Being in standalone 5 gal DWC buckets, I do have to add more water and nutes back every few days, and every day when they get to late flower and eat/drink a lot more.

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So if I understand correctly:
You make a big res with nutes.
And from this res you top up your buckets whenever it is needed?

Keesje said:

On another forum there is a discussion going on for how long you can work with the same res/nutes.
Some say just a few days. Others claim they run it for a month.

Of course it is depending on how large your reservoir is.
But for discussions sake let's say it is huge.
For how long do you guys think you can run it?
And also please share some experiences or how you do it.

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They drink so much water daily, that your constantly adding in fresh water and nutes so its truly never in this case.

For the most ways people on these forums grow, plants drink a maximum of 15 liter per square meter per day.
(But when they are smaller, of course they drink less)
So lets - for discussions sake - say that you would have a res of 450 or 500 liters and 1 square meter of plants, there would be enough water for 30 days.

My questions are more about if it is possible to keep your reservoir for this 1 month.
Or will it go smelly or bad?
And will - if you use the res for a Flood & Drain system - get out of balance in such a way that it will harm the plants?

My last couple runs I havent even changed my res. Im sick and my back is killing me so I have been down to the leanest of essentials to make my grows work. I top off my res when the flood table starts to blow bubbles from the pump. My res looks just as nice as any of my other grows that I was changing the res every 4 wks. Kinda looking back now like "what a waste of time, resources and energy".
@Axion42 right on point with keeping your ppm/pH in check, keep the light out of the res and good water temps.

HydroRed said:

My last couple runs I havent even changed my res. Im sick and my back is killing me so I have been down to the leanest of essentials to make my grows work.

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Sorry to hear about your sickness.

For how long do you think you could stay with the same res without adjusting the ppm or the pH?
Let's pretend your res would be big enough.

Sorry, Im a little confused with your question. You mean still top off with fresh water, but never adjust the pH or the ppm?

Sorry, let me try to explain a bit better.
I saw on your link that you grow F&D with 2 trays of 40" x 36".
Now lets pretend you would have a really large reservoir for every tray.
So big that you would never have to top up during the whole stage of flowering.
For example 200 Gallons per tray.

How long do you think you could keep the res without adjusting ppm or pH?

I am not suggesting that it is a wise thing to do But I am trying to find out what members' experiences and thoughts are about this.

Keesje said:

Sorry, let me try to explain a bit better.
I saw on your link that you grow F&D with 2 trays of 40" x 36".
Now lets pretend you would have a really large reservoir for every tray.
So big that you would never have to top up during the whole stage of flowering.
For example 200 Gallons per tray.

How long do you think you could keep the res without adjusting ppm or pH?

I am not suggesting that it is a wise thing to do But I am trying to find out what members' experiences and thoughts are about this.

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Ok, I think I gotcha now. If I never had to touch my res for the life of a grow, I'd probably get about 2-3 weeks out of it before pH would swing upwards to an unacceptable level and my ppm would drop greatly due to plant uptake. I would guess thats probably about the time my plants would start letting me know they werent happy with the res conditions. This is a very uneducated guess though and not really any "science" behind it so take it with a grain of salt lol. Hope this was helpful in what you were wanting to know.

Sure it helped.
I am trying to collect as many experiences as possible.

Keesje said:

Sorry, let me try to explain a bit better.
I saw on your link that you grow F&D with 2 trays of 40" x 36".
Now lets pretend you would have a really large reservoir for every tray.
So big that you would never have to top up during the whole stage of flowering.
For example 200 Gallons per tray.

How long do you think you could keep the res without adjusting ppm or pH?

I am not suggesting that it is a wise thing to do But I am trying to find out what members' experiences and thoughts are about this.

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If the res was large enough I'm confident that I could leave it through a whole grow. With the nutrients I'm currently using the ph doesn't seem to hardly change. Its been 2 weeks since I changed my res completely and I have topped it off with some plain water once, and with some nutrient water once to raise the ppms to meet plant needs. I havn't had to adjust the ph at all though.

Keesje said:

So if I understand correctly:
You make a big res with nutes.
And from this res you top up your buckets whenever it is needed?

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Basically yes. Because I do standalone 5 gallon buckets, I have to do this process to each and every one of my buckets. But if you have a system that allows all of your bucket/plant sites to access the same water, you can do it that way. I don't advise waiting 2-3 weeks between res changes like I do, but if everything is going well and your PH is stable, let it ride No point in doing a res change if everything is in balance...besides, it can be easy to stress your plant during a res change.

Thundercat said:

With the nutrients I'm currently using the ph doesn't seem to hardly change.

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If I remember correctly, you purchased a brand that is only locally available.

Logan Burke said:

No point in doing a res change if everything is in balance...besides, it can be easy to stress your plant during a res change.

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I have heard this (stress icm res change) from a lot of growers.
Might have to do with the different temperature, or the EC or pH from the new res that are totally different from the old res.
I don't know exactly what would cause it.

Keesje said:

If I remember correctly, you purchased a brand that is only locally available.

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Nope it's not local, they just don't sell it in many stores, you have to order it. It's called ENVY it's a great product.

Thundercat said:

Nope it's not local, they just don't sell it in many stores, you have to order it. It's called ENVY it's a great product.

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I guess only in the US then.

If it is this.
http://www.envybrand.com/index.php/envy-hydroponics

Two nft tanks gt24 and gt100.

GT100 (100l ) auto topped up from a 120l water butt. Fresh water. I use a mini ATO auto top up system. My water is fairly soft.

The plants drink a lot of water, I just add nutes once a week and pH down twice a week. 4 or so ml each time brings it down from 6.5 to 5.5 (rockwool). 2ml in the GT24 tank.

When buds start forming I drain the tank with the pump, fill fresh, new nutes, then leave to auto top up again.

Last flush is 3 days before harvest. Fresh water only.

So that's two flushes throughout grow only. Mid flush is probably not needed but it's easy, so I do. I let the tank heat back to 20c before switching the pump back on.

Was same with GT24 but only have one top up system so GT24 is manual now.

I run a 5gal RDWC with a 30gal top of Res out of the tent. I top off once a month sometimes less and that is only to track PPM intake more accurately. I have a small submersible pump that tops up my grow tanks twice a day flooding them for 15mins to exchange all nutrients. The grow tanks all have oversized drains that run back into the Res so it is fool proof. I keep bubbles in all tanks and track pH and PPM every 1-3 days on a chart. When you have large reservoirs you do not want to change the tank often because youre basically throwing good nutrients and money down the drain. Keep the water oxygenated and sterile and you can run the same tank for months. Keep in mind that topping up nutes depending on Plant stage is key, nitrogen is hard to add as a solo nute through mid veg so people sometimes dump their whole tank in order to avoid stacking PK. Plenty of bloom nutes are available though so topping up PK late flower is easily achieved without dumping the whole tank.

Blent said:

I keep bubbles in all tanks and track pH and PPM every 1-3 days on a chart.

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Great post with a lot of useful information!

How often do you have to adjust your pH?
What brand of nutes are you using?

Keesje said:

Great post with a lot of useful information!

How often do you have to adjust your pH?
What brand of nutes are you using?

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I let it swing around but keep it between 5.6 and 6.1. the best thing about keeping a chart is you don't panic when you see it slowly trending one way or another. Sometimes treating the symptom isn't going to do you any favours... For example if your growing sterile in rdwc system and you notice a sudden shift in pH you could need to top up your steralizing agent because bacteria has managed to multiply or top up your water to dilute the salts. Temperature also plays a part but not massively.. I think anyone would drive themselves mad trying to stay within 0.5pH of their perceived optimal number, that's why tracking your trending pH is the best thing to do.
I try to use less of the pH up down products if I can help it, usually the drift will go down and topping with tap water lifts that for me.
I use a local blend 2part dry nute 20.10.40 and I boost PK later in the cycle. Plus a few basics like calmag and I keep sterile but try to use less chemicals rather keep the Res temps low and no light leaks. I also have the privilege of fresh alpine water.