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

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.

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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I run an aeroponic system that has a 7gal res with a float valve keeping water levels steady, I mix my veg nutes and dont change res until I flower. Also do the same while flowering I never change until plants are done. I also have a 27gallon tote that houses 4 mother plants with a 4 gallon res attached for checking pH ppm ect. I'll run same water/ nutes for 4 months until I take new cuttings and replace mothers. Keep your pH and ppms reasonable, keep water temps in check and keep light out, and you shouldn't have a problem, I never do but everyone's environment is different.

Axion42 said:

I run an aeroponic system that has a 7gal res with a float valve keeping water levels steady, I mix my veg nutes and dont change res until I flower. Also do the same while flowering I never change until plants are done. I also have a 27gallon tote that houses 4 mother plants with a 4 gallon res attached for checking pH ppm ect. I'll run same water/ nutes for 4 months until I take new cuttings and replace mothers. Keep your pH and ppms reasonable, keep water temps in check and keep light out, and you shouldn't have a problem, I never do but everyone's environment is different.

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Do you adjust pH in the reservoir in the flowering stage?

Keesje said:

Do you adjust pH in the reservoir in the flowering stage?

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Of course. I just use tap water, comes in at about 8.2pH, if you look in my aero setup the 5gal bucket to the very right only holds water, that bucket is connected to my 7gal res (control) via float valve. So with my tap water being 8.2 my nutes are somewhere in the 5s..it balances out pretty well I can go about 7 days without adding pH up or down depending on how much the plants are feeding. I average about 4 or 5 days before I have to adjust most of the time.

My dwc veg setup is a little different Usually about 2 or 3 days pH is swaying so I have to adjust

Axion42 said:

My dwc veg setup is a little different Usually about 2 or 3 days pH is swaying so I have to adjust

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Thanks already for those answers.
Did you notice any bad smell after a week or 2 weeks?

I used to do flood and drain with very large reservoir (200 gallons for a 4x. I ran the res the whole flowering run of 60 days.

Renfro said:

I used to do flood and drain with very large reservoir (200 gallons for a 4x. I ran the res the whole flowering run of 60 days.

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Wow. That is impressive.
With no topping off? No adjusting the ppm?
But I guess you had to adjust the pH?

I just added water (RO filter thru float valves on a timer that made sure the trays were drained before activating the float) and kept the ppm, it took 15 ml micro and 30 ml bloom daily per light (2 over a 4 x 8. pH was very stable, never had to mess with it. I was running lucas at the time. I am sure it could have run a while without adding nutes but I just kept it at 1000 ppm. PPM dropped about 15 per day.

Plants drink so much water in hyro that topping off is frequent,so your not really using the same water.

Keesje said:

Thanks already for those answers.
Did you notice any bad smell after a week or 2 weeks?

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Nope just the smell of healthy white roots.

myke said:

Plants drink so much water in hyro that topping off is frequent,so your not really using the same water.

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I don't get what you mean.
could you explain a bit more, please.

Theres several different ways to grow hydro,some like rdwc need to keep a static water level.Others like top feed or ebb and flow only need to be filled once the rez is near empty.

A large plant will consume 5 litres of water a day at least.

I've got a 40 gallon res and have left my 4x4 tray for 9ish days while I was on vacation. The res was nearly empty when I got back, but the plants were crazy healthy and happy. They had grown like crazy while I was gone.

myke said:

Theres several different ways to grow hydro,some like rdwc need to keep a static water level.Others like top feed or ebb and flow only need to be filled once the rez is near empty.

A large plant will consume 5 litres of water a day at least.

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I did read my opening post again and it is a bit unclear. My fault.
I mean for E&F or for a system like DWC with an external reservoir.
Or Run To Waste with a huge reservoir.

Again dwc needs to maintain a certain level.
If someone says they go a month without top ups then you probably shouldn't be reading there posts.

I thought I would add that I usually only go about 3 days . I try to keep a decent eye on things.

myke said:

Again dwc needs to maintain a certain level.
If someone says they go a month without top ups then you probably shouldn't be reading there posts.

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I know people who have DWC with an external reservoir and they top up with a valve automatically when the level reaches a certain point.
In that case it is possible to keep the nutes longer.
The questions are "how long can you keep the nutes in this reservoir before they get bad" and "at what point will the single elements in your nutes be out of balance, in such a way that it will harm the plants?"

Ok I see. Kinda of like going on a 3 week vac. And you got no one to babysit.
There’s a thread just recently about this.In drain to waist. Something about how much can u mix at one time.

I run DTW and have a 27 gallon rez but add only 15 gallons. This gives me 4 days of solution and the last cycle of the rez, about two gallons, I add Great White and run the rez empty. I then rinse and wipe down the rez prior to refill.
Estimate about three gallons per day with at least 30% runoff.
Here we are at day 22 and 24 of 12/12.