Sure, corrosion (generation of oxides, sulfides, or salts) or simply free metal ions that are dissolved into liquid can go uncaught. The rate at which this occurs would be the concern. A metal that is slow to corrode will take longer to detect and likewise would be contributing less metal ions into the solution. Stainless steel is generally slow to corrode in mild environments.
Think of this, most homes contain copper pipes for water. An exceedingly small number of copper ions are transferred into the water. The longer the water sits in the piping, the PH of the water, the temperature, and the mineral content determines the amount of copper in solution. You generally do not see the corrosion because you cannot view it and, under normal circumstances, the process is slow, slow, slow. The amount of copper in residential tap is likewise exceedingly small.
For a hydroponic system, folk have seen issues when using brass or copper in recirculating systems over extended period of time. Possibly, copper toxicity. Plants are sensitive to copper. @MicroDoser and @anon32470837 have experience and some testing with metallic toxicity in solution. Take a look into their threads and their experiences.
Stainless, though, is much more resistant than copper. The compound I’d be most concerned with would be nickel and chromium. Maybe aluminum. Though, I don’t think you’ll have a lot of problems here unless you are soaking the metal in chlorides or you never ever change the solution out.
But, again, if you can find a plastic fitting that is suitable that would eliminate the dissolved metals concern. Also, consider that nothing lasts forever. Building an increasingly reliable system also means that you are probably spending extra for higher quality components. I, personally, prefer reliability but sometimes it is equally wise to consider the trade-off of regularly replacing certain components instead of spending extra dough. Over time, you’ll be able to figure out where the extra money is worth the expense. Then upgrade.
Yup, I can confirm that using copper leads to sulphur def, and iron leads to a P def eventually. I will say though that it took the iron casing to be very very rusted internally for any def to show up, a year or two at 5.8PH and a few runs with bleach. Copper piping causes a sulphur def almost immediately, no bleach or acid required. 12 brass fittings (15mm gate valve) used in a 100l recirculating system with 12 plants will gradually trend towards a sulphur def when they start to corrode. In my case all it took was 3 hours at 2PH and a dose of bleach to get them to start dumping much more copper into the water, although the valves were about 4 years old by that point.
I spent about a year trying to figure out deficiencies etc, looking at RH%, PH, and various things until I found out it was metal toxicity. Now though, I know nothing is wrong with my environment because I have addressed every aspect of it trying to chase down the defs…
I have shifted the way I view quality, product life, replacement schedules etc recently.
I used to buy a part, and when it failed I would replace it. Some parts I would buy a basic part, other parts I would buy higher quality. Most often it would be active parts, like pumps, that would get the most money thrown at them. Then I noted the cost of the failures.
Now, I think “What would it cost me if that part failed?” which sometimes leads me to have one of those parts just sat around to swap in, sometimes I shorted the replacement schedule, and other things get a very very good quality part and a spare sat around and a short replacement schedule. If my pump fails I don’t even want to wait the time it takes to go to the shop to replace it.
I also think “What is the way this part fails?” some parts just stop working, this is for me the ‘best’ failure. It is ‘failsafe’. Sometimes though they fail in a destructive way like corrosion or leaks. These failures can cause secondary problems or cascading failures. For the first type of failure, I just keep a spare and try to replace the part before failure. For the second I see when it starts to cause issues and replace that part with a much harsher schedule, ideally half the time between fitting and a problem.
I generally find that the cost of a failed or corroded part is around 1% of the cost to my plants from it failing. I keep finding higher quality parts, at higher prices, and so far the cost is easily justified. While I got it cheaper the R.R.P. of my main pump is around £800. Plastic head, magnetic drive, no metal in contact with the solution. I got it precisely for the reasons this thread was made, to limit metals leaching into my nutrient solution causing lockouts/deficiencies. The recent costs of not having that pump are heading closer to ten times that amount.
Of course, all this depends on how important it is for your plants to reliably grow in a healthy manner. Some people are fine with a failure every now and then. Losing 1/4 of your yield, or losing half a cycle refitting things is not such a big problem to some, but if getting a certain yield, or keeping to a particular timetable are important things then you should at least consider making a chart or calendar with all your parts and when they need to be replaced marked on it to remind you. It is good practice anyway.
I feel your pain trying to find plastic parts, I am hunting for 15mm gate or ball valves so I can stop using brass ones. All the plastic valves seem to be 4 times the size of metal ones, understandably, and none I have found fit 15mm plastic piping. I may have to change my whole system to be 22mm throughout.
I know I have a year or two to do that before my brass fittings start to become a problem, and when they do I know the signs now. This, for example, is too much copper. Too much iron shows later in flower and manifests as a P def where older leaves suffer necrosis starting at the leaf edge.
After swapping out the brass valves for new ones, improvement happened almost immediately, within the week.
EDIT :
I would say the corrosion would be visible to the eye, although it may be internal to the valve/pipe/pump. When my brass fittings needed replacing they looked like this. Externally my pumps looked fine but when I looked inside investigating my problems they were very very rusted indeed.
I would say if the internal surface still looks new, the chances of toxic levels of metals leaching into your solution is low.
How can I find out what is the source of these nutrient deficiencies?
Plants are in 3 weeks bloom.
Now even of some newer leaves of some plants there is already yellowing. Why is that? But I am not sure, maybe it is some bleaching with the newer leaves.
Btw, do you know if the hunter solenoids which are for lawn irrigation are good for use with fertilizer?
In order of operation, I always double-check PH. Then if PH is good I refresh the nutrient solution.
Your problem there looks to me like a P def, which is rare and suggests either incorrect PH or contamination. It could also be magnesium which is also likely if you have an RO system. Both would be fixed by fresh nutes and correct PH. Check your PH, if it is over 6 it could be the cause of a P def, if it is under 5.8 that could be the cause of a Mg def.
If that does not fix the problem then your problem is not a lack of nutrients, nor a lack of availability from incorrect PH. If that is the case, iron may be leaching into your nute solution.
Once you have eliminated the most common causes, check for any metal parts or other possible sources of contamination. After my experiences in the last year, I would no longer have any metal parts in a recirculating system in contact with the nutrient solution.
I am unfamiliar with Hunter solenoids, sorry. Maybe find some technical specs or a datasheet.
IME parts designed for run to waste flow are often unsuitable for recirculating systems.
Hmmm, I get these mixed up all the time and sometimes think “P” when it is actually “K”, etc. Perhaps, it’s just me. But, as a reminder:
Potassium uses the symbol “K”.
Phosphorus uses the symbol “P”.
Also, these charts are based on nutrient availability before they start to get “locked out”. The transition from available to unavailable is not necessarily a hard cutoff as visualized in such graphics, but rather it decreases outside of the optimal range. It becomes more difficult for the plant to uptake the mineral as the chemistry of a mineral species changes due to the PH change (also somewhat dependent on the overall chemistry in the system).
I believe that there is some interpretation when generating such charts. They are more intended as a rough guideline.
ok I changed the nutients completely. After I put in the nutrients in the RO water, it has a ph of 5.3. What you suggest where I should start with my ph considering the actual state of the plants? Low or high?
If it drifts downward, start at 6.1 and let it drift to 5.5, if it drifts upward start at 5.5 and let it drift up to 6.1.
The state of the plants is they are not uptaking a nutrient (main suspects potassium/Mg), the differing info in the charts leads me to want more solid info before I would say “Be at X PH”, so I would cover all the bases and over a few days cover all the range between 5.5 and 6.1.
If your plants do not show recovery after a week, you do not have a PH issue and you have another issue. Mine was excess metals leaching into the solution causing lockout of certain nutrients.
I suspect RO water is more open to leaching stuff from the environment than plain tap water, possibly due to osmosis or some chemical thing that makes it more reactive (chemistry is not my hot subject). Either that or shop-bought CalMag is pants and does not do what it says on the tin.
I am still chasing down the exact cause of this particular def.
I changed the nutes and my new plants dont show any deficiencies at the moment. Only the old ones. So i think I damaged the old ones too much and maybe there was something in their cubes.
Ahhh I dont know what to think about my old plants. They are looking all kind of colors and directions. But they seem to yield and the leaves on the buds look good. I will see how much they will yield. And the new ones are looking pretty good.
I have a very similar issue with mine that started when I got my RO unit. @anon32470837 also had the same issue when he got an RO unit.
Regarding yield, I found no impact on yield even with quite bad necrosis. The opposite in fact, I had 1.3GPW under HPS in 11 weeks including veg time.
I am in the process of figuring out what to do about it, the next thing I will be trying is a wider PH swing, once I rebuild my PH sensor and get a new dehumidifier that does not have an ioniser built-in as they drastically affect the circuit I use for measuring PH and make the readings meaningless.
I have already tried ever-increasing amounts of CalMag, as well as individual bottles of calcium and magnesium also in increasing amounts, to no effect.
If there is not a lack then something else is causing the def. The next obvious culprit is PH.
interesting. I was handling the first plants pretty rough. It is my first hydro grow and switched from co2 with no air cooling ( temperature on the last day up to around 45 degree celsius) abruptly to cold external air with no co2 (down to 10 degree celsius in the night). I even damaged some plants so badly I had to remove them and a lot of plants stayed pretty small and thin all their life. Also I think I fucked up the nutes a bit in the process.
In that process I selected a couple of plants for mother plants which survived everything with almost no damage. (The best 10% percent). Then I took many clones from them (again around 150) These new plants dont show any signs of problems… I just hope these plants will have a yielding genetic. Some of the clones that I selected seem to grow aggressively. They increase in size four times after inducing flowering (only 1 to 1,5 week rooting first). They even grow very close (maybe 6 to 8 inches) to the 600W double ended bulb and the leaves dont seem to change. Just the buds get bigger…
So I think with the batch of selected plants, I can’t say if I got the nutes now right or if it is just more robust plants…
Maybe you can do a test grow without the ro water?
btw how is ionization of the air affecting the measuring of ph in the nutes? is the ions ‘leeching’ from the air in to the nutes?
Personally, I grow indoors with a variety which was crossed to be grown outdoors. It has amazing growth, branches a lot without topping, can handle very high humidity (RH% 90+) without risk of mould, and continues to put out roots strongly well into week 6 of flowering.
Forced evolution is a great way of selecting plants. Treat them cruel and whatever survives can handle it.
Regarding PH, the way that a digital PH meter reads PH is by detecting the incredibly tiny differences in potential between your nute solution and a fixed reference solution (the liquid inside the PH probe). It measures the changes in the number of ions crossing a glass (or plastic) barrier.
As you can see, having loads of rogue ions floating about in the air and nute solution would make your readings way off. It also seems to have permanently affected the internals of the IC on the circuit I use to measure, probably by overloading some internal section which is incredibly sensitive and short-circuiting it, essentially with a relatively high static charge or similar. This would still, to us, be a very very tiny charge but it would be far too much for the PH circuit. I first noticed this effect when I used a floating pond ultrasonic mister, the ultrasonic process ionises the mist…
I would consider doing a run without RO water if I were getting reduced yields. As it is, the damage seems mostly cosmetic although I suspect I actually do have reduced yields from the amount possible with my system but the increase from running RO offsets that.
I will instead just try to figure out the true problem and then see if yield increases as a result.
thanks for that … been years in industrial settings …I know what a check valve is never seen a non-return. If you don’t want a return you just pipe it away in my head. lol
The second illustration show a spring to ensure closure and a specific ‘crack’ pressure to open it back up. They serve a similar purpose but you generally can’t claim backflow protection for a swing-gate or ball non-return valve (NRV). A check valve will have a bunch of parameters ensuring performance such as crack pressure. An NRV generally does not provide that information. E.g. if a local ordinance demands backflow protection, technically an NRV likely will not satisfy the requirements.
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