How do I flush during flowering?

[jimbojones5678]

I'm interested in some suggestions in regards to flushing my WR, I have had the nutes at 1.5 - 1.6 for nearly two weeks now and I am due for a res change. I've read a few differing opinions on flushing between res's and am not sure whether to flush at all, flush with a low EC level nute batch or flush with PH adjusted water.

Also how long do I flush for? Should I just run the flush through for a couple of ten minute feeds or for a whole day?

 

Jimbo

[WantDaChronic]

proper flushing uses only pH adjusted water, but imo you only need to flush like that when close to harvest or when you have plant issues...a low level batch of nutes does wonders every now and then though

[Luke Skywalker]

I would regularly run pH adjusted, perhaps a mild solution, (like 0.4 ec) through the system with each change of nutrients. You can do this every two weeks or so, although if your water quality is suspect, (over .5 e.c. out of the tap) it's certainly a good idea to do this weekly.

 

Run fresh, pH adjusted water (with or without mild nutrient) through the system for 10minutes at a time, and then check the e.c. of the solution. In RTW it's a bit quicker to do as you're not recirculating the same salts over the media. Once that 10mins is up, allow the pots to fully drain then check the e.c. of the runoff/reservoir. You want to flush until you get the e.c. to within 1 point of the solution you're flushing in.

 

i.e. I have a plant in a recirc system and after a 10min flush with 1.2 e.c. (0.4 ec nutes and 0.8 e.c. tap water crap) solution the tank reading is around 1.6. After dumping this and then refilling and running a second flush, it might be down to 1.3 or so, which is the target e.c. You can eventually get the rootzone back to the same e.c. as the water it's flushed with, but this takes a lot more flushing than it does to bring it within 1 point and this is for all practical considerations plenty clean.

 

Some don't flush during the grow at all, and that's perfectly fine provided you're not seeing a regular rise in the e.c. to dangerous levels, (above say 2.8 or so). Check the runoff from the pots, see how many points above the input solution the e.c. is and then you can decide whether a flush is a good idea. During the early stages of growth you may not need to do this much, but once the plants reach the flowering stage they certainly benefit from it IMHO.

 

Lucky bastards like me with R.O. water are able to leave flushing to once every two weeks, but those with crap water are well advised to do a regular weekly dump, flush and reformulate.

 

Hope that helps, and if I've described things a little abstractly just let me know and I'll try and put it more concisely.

[Stoney]

hey there

 

if you are just using normal nutes and no additives such as superbud or rock juice then i would only flush befor going 12/12 this will get rid of any build up of salts in ya medium and then a final week long flush at the end of flower this will get rid of any nutes in ya plants and leave them with a good taste

 

now as i use rock juice i flush at the start of 12/12 and then after the rock juice has done its job and then at the end befor harvest

 

i only use ph adjusted water and keep changing the water over untill the ppm or ec matches the ordinary water that way you know you have got ride of all the salt build ups

 

but as i said if you aint using any additives then just flush befor 12/12 then befor harvest and all will be good

 

cheerz :Dj:

[loylty gets u nothing]

tonight i noticed me run off to be a bit high

im at the end of week 4 it was reading 3.2ish

so i made some nutes half that strength 1.6 ec

flushed a good 50ltrs threw me 25ltr pot and ended up gettin ec 2.0

i handwater u recycle i think

i wouldnt wory to much unless ya got high reading

all the best

bil

[Luke Skywalker]

See, the thing is this buildup isn't usable nutrient if your water is crappy. What happens is as you add more and more salty (relatively) water to the tank, and then the plants take out the ions they want. They do take up a little sodium, and it will do this at the expense of potassium. But there is only so much it can take up, and the rest is left behind....

 

So, you've got water which has been depleted of nutrient but not sodium, and then you add more solution which contains yet more sodium and nutrient.... This buildup can quickly reach toxic levels and seriously harm plants.

 

I thoroughly recommend people undertaking a regular flush in their recirculating hydroponic systems. Send an email to your local water supply, or give em a call, and ask for a water analysis for your catchment/supply. This is a normal request, not at all out of the ordinary, and they'll send it off to you lickety split.

 

If your water analysis shows a large ppm of sodium with an e.c. above .5, (usually it's a range they give you, like .3 - .5 or something) then flushing isnt' just useful, it's practically warranted.

 

Don't get me wrong though, you can grow some marvelous crops without flushing during the crop cycle, but it becomes harder and harder to manage if you've got a crap water supply. The results of using cleaner water, from experience, are well worth the efforts. The quality and rate of growth with good water supply are fantastic. I have gone to the extreme length of having a large water tank of Reverse Osmosis treated water, but I also have an orchid collection which warrants that. If you can't afford or be bothered with R.O., (and I can certainly understand why) then I highly recommend using a regular flush of the media, (with or without a mild nutrient added, I've yet to see significant damage without it, but I can understand the argument for doing so) to cleanse excessive sodium and other unwanted ions from the media.

 

In Run-to-waste systems, ensuring a runoff percentage of at least 50% with high e.c. water is recommended. This ensures that any excessive buildup of sodium is leached out and replaced with each watering. You may have heard 10 or 20% as a recommended runoff rate, but this is when using high quality water. The worse your water, the more the runoff per watering is required for rootzone maintenance.

 

The roots are the mouth and ass of the plants. Imagine your ass and mouth stuffed with shit and food respectively, and you're already full. Then keep shoving it.... That's kinda whats happening here.

 

And on that strange image, I hope that helps.

 

All statements are IMHO, don't want to tread on anyone, but I feel this stuff is important.

[jimbojones5678]

All statements are IMHO, don't want to tread on anyone, but I feel this stuff is important.

I don't think that you are treading on anyone as everyone is entitled to their opinion; especially when it is derived from practical experience. I think this stuff is very important as well - I have built a custom enviroment to maximise the plants potential so I want to understand everything that's going on in the system. IMHO there is little point in going to all the effort of constructing and maintaining good indoor conditions only to take a shortcut or nelect one point of the whole thing. sure some people are more pedantic than others but for me - as this is my first solo effort, I can't help but want to try and get the grow going as strongly as I can.

 

I understand the possibility of sodium build-up by just constantly topping up with nutes when the EC go's down - and that there is no real way of nowing what has decreased in the mix - and that's why I'm interested in knowing what methods others use. All the info I've retrieved from this site has got me this far - and the girls are looking ok to me so far! - and I think that you can only make a informed choice if you listen to a few peoples opinions, when you don't have prior experience like me.

 

I use filtered rainwater EC <0.2 in a recirculating system - 10mins an hour and one during lights off. I flushed with straight PH adjusted water at the end of vege but wasn't sure if I did it right? I now understand that I am looking to get the runoff within 0.1 - last time I only knew why I was doing it but I didn't understand how to tell when I had done it enough.

 

My plants certainly don't show any signs of deficencies or buildup but it was a long vege and I did run some nutes through it that were too strong. I think I'll flush it this week to see what the readings are just to be on the safe side and to get the experience. It can't hurt can it?

 

Jimbo

[Mr White]

I wonder how i got this far.

Growing in coco, RTW ,and feeding each plant about 2.5 lts per day(getting less now) @ 2.4ec and alowing about 20% runoff.

Never check the runoff,but did last night and got a reading of 5.8ec.

My water out of the tap is .8.That is quite a build up would you say.

Only have about 2 weeeks to go so i am starting to Half the dosage this week and only ph adjusted water the weeks after till harvesting.

Have never done a flush to this lot yet.

The only probs ive had was them getting to big,and that was my fault.

I may have been very lucky.

[Luke Skywalker]

Quite possibly, although one should keep in mind that we are dealing with Gross Feeding plants, which can take quite a bit of punishment.

 

Still, IMHO, it's an important part of getting not only quantity, but quality.

 

Rootzone conditions are exceptionally important, and yet we spend most of our time just getting the GR conditions right, and tend to leave the roots to their own devices....

[jimbojones5678]

Gross Feeding plants, which can take quite a bit of punishment.

What does that mean? I'll Google it anyway but I'm keen to hear your explanation anyway.

 

Still, IMHO, it's an important part of getting not only quantity, but quality

A mix of both is nice but I would rather quality over quantity anytime too.

 

Rootzone conditions are exceptionally important, and yet we spend most of our time just getting the GR conditions right, and tend to leave the roots to their own devices....

Exactly what I said but shorter....well done!

 

Jimbo