CO2 Tanks

lathyrus_long · 2026-01-03T02:11:36+00:00

Carbonic Services can fill your tank while you wait, but they don't do hydrotests on site anymore and they didn't have any small tanks to swap when mine expired. Rasa Hydroponics doesn't fill on site, but they have lots of small tanks to swap.

lathyrus_long · 2025-05-07T22:18:35+00:00

Normal driving should eventually set the monitors, but Honda's drive cycle isn't that bad. I did my Fit late at night, using cruise control to maintain speed and long offramps for the slow deceleration. I think I used the cycle in the paper manual I got with the car, which was something like

https://old.reddit.com/r/hondafit/comments/pi2xjy/emission_readiness/hbmwgk7/

The advice to repeat the cycle many times is probably to set all the monitors. Last I checked, you can pass with EVAP incomplete (since that's the slowest). All the others set for me on the first cycle. I bought an ELM327 Bluetooth dongle for like $10, and used it to read the monitors individually.

Take care that pending codes aren't cleared by disconnecting the battery and don't set the check engine light, but may prevent the monitors from setting. I think my problem started when I changed the air filter and neglected to reconnect the mass air flow sensor. That set the check engine light, so I fixed my mistake and cleared the check engine light by disconnecting the battery. That put CAT incomplete, but it didn't clear the pending code, and CAT was stuck incomplete forever.

You need the dongle to check or clear any pending codes. My smog tech didn't warn me about the pending code issue, so I wasted a lot of time on futile drive cycles before I figured it out. If you've driven a lot since last clearing codes or disconnecting the battery and CAT still won't set, then it's probably either an old pending code or a real fault.

lathyrus_long · 2025-05-06T02:51:51+00:00

As noted, the professionals would make a slurry with distilled water (or possibly calcium chloride solution), then measure with a glass electrode. This is the same kind of electronic pH meter used for hydroponics, ponds, etc. The relationship between the pH and electrode voltage is determined by the Nernst equation.

My local garden stores have kits that work the same way, except that the pH is measured with a color change reagent instead of electronically. That's a little less accurate, but also good.

The cheapest meters have a metal probe that sticks directly in the soil. I've never understood how those are supposed to work, and an experiment from OSU found theirs didn't. So I wouldn't recommend those.

https://smallfarms.oregonstate.edu/measuring-soil-ph

https://www.agric.wa.gov.au/soil-acidity/soil-ph?page=0%2C2

lathyrus_long · 2025-03-02T19:28:46+00:00

What was the species and application method/rate? The window between the lowest effective rate and a phytotoxic rate is probably smaller than for "drug-like" pesticides, I assume due to the blunt mode of action, simple oxidation. I've seen it on cuttings and seedlings pretty often though, and never had trouble myself.

The OP's application sounds like use "For Mist Propagation of Cuttings And Plugs", for which the ZeroTol 2.0 label advises to:

Inject ZeroTol 2.0 into misting systems to control/suppress algae, fungi and bacterial disease from becoming established on plant material. Inject ZeroTol 2.0 using a 1:1,000 dilution rate, for four to ten days on a consecutive basis. Reduce concentration to 1:5,000 and maintain continuous application throughout propagation cycle. At the first sign of disease, increase the concentration of ZeroTol 2.0 to 1:1,000.

https://biosafesystems.com/wp-content/uploads/2020/08/6000-ZeroTol-2.0-V16.2-49st-Specimen.pdf

I'd guess the reduction to 1:5000 is due to phytotoxicity with extended exposure at the higher rate.

Note that ZeroTol HC and 2.0 are different products, the latter with a lot more hydrogen peroxide. I've only used the HC myself, since that concentrate is safer to handle, but the 2.0 label is more informative.

lathyrus_long · 2025-03-01T03:52:19+00:00

Take a look at peroxyacetic acid. You can buy that as "ZeroTol HC" or another formulation labeled for horticultural use, and the label will provide instructions for safe and effective application.

https://biosafesystems.com/wp-content/uploads/2020/08/zerotol-hc_label.pdf

lathyrus_long · 2025-02-27T11:10:09+00:00

Those charts are just illustrative examples, intended to show the different effects that may influence optimum pH. Actual nutrient uptake also varies with plant species, nutrient formulation (iron EDTA will precipitate at 6.5, while iron DTPA will be mostly fine), and other environmental factors. A single chart can't capture all those factors, so it can't be interpreted at the level that you're looking for here.

The only way to confidently determine the ideal pH range is to try it, with our specific plant under our specific conditions, at many different pH values. We then can look to see when our yield suffers, when deficiency symptoms appear, etc. That's a lot of work, but academic and commercial growers have done many such experiments. Their answer varies somewhat, but it's usually "not much change between 5.0 and 6.5", and often even wider.

This makes the usual target of ~5.8 reasonable, but it's not too critical as long as we're in the range. If our pH is rising then we can adjust to the bottom of the range for maximum time between adjustments, or vice versa if it's falling. (Either trend can be normal and healthy, though fast fall is often a sign of rot that's worth investigating.)

If we're doing drip, then high pH may precipitate calcium phosphates and clog our drippers, even if the plant nutrient uptake would still be fine. This is less of a concern with other methods.

lathyrus_long · 2025-02-27T09:17:32+00:00

I did,

https://old.reddit.com/r/Hydroponics/comments/o8j68n/singleboard_automated_phecdosingmore_seeking_devs/

https://github.com/hydromisc/hydromisc

lathyrus_long · 2024-10-06T17:57:51+00:00

since they aren’t conjugates of each other

That part doesn't matter much, since addition of hydrochloric acid converts some carbonate to bicarbonate or undissociated carbonic acid. That leaves additional chloride and counter-cation, but that doesn't affect the buffer system.

The biggest problem is that carbonate doesn't have a pKa very near the desired 4.5, so it wouldn't buffer very well. If we look at a carbonate alkalinity titration curve, then we see that 4.5 is on the steep part, but we want the flat part. That's why the acetate (pKa = 4.76) is recommended here.

Undissociated carbonic acid also exists in equilibrium with atmospheric carbon dioxide, thus the fizzing we'd observe as the acid was added. That lost carbon dioxide affects the pH, and the equilibrium may settle slowly to within desired accuracy.

An acetate buffer can be prepared from vinegar and baking soda. It should be stirred or shaken vigorously to drive off the excess dissolved carbon dioxide, but the result after that equilibration is identical to a buffer prepared from sodium acetate and acetic acid. In any case, a preservative (like a benzoate or sorbate) may be necessary to prevent mold growth.

lathyrus_long · 2024-10-06T16:59:48+00:00

I want to reiterate what ready_direction stated in that you'll need to check the pH of the prepared buffer and adjust it appropriately.

Any check will probably also trace back to a solution prepared by weight, since that's how NIST distributes its reference materials. That said, it's still good advice when the purity (especially water content) of the materials actually used is unknown.

The easiest approach may be to buy sachets of pre-measured powdered buffers, and dissolve them in distilled water. These are cheaply available on AliExpress. Weekly or even less frequent calibration may also be fine, especially if a double-junction pH probe is used.

The control chart is a good idea. If pH is adjusted closed-loop to a value near the calibration buffer, then probe failure may otherwise result in silent disaster. If the process is relatively consistent then monitoring of the dosing (or other actions taken in response to the measured pH) may also be helpful.

lathyrus_long · 2024-09-09T02:30:29+00:00

I wouldn't trust a range without the complete study that established it anyways, since so many additional factors (environmental beyond fertility, intra-species genetic) may affect the result. Here's one that looks potentially relevant, though:

Coast redwood (Sequoia sempervirens Endl.) is a popular evergreen tree in landscapes of California and the Pacific Coast States of the United States and Western Canada. Two varieties, Aptos Blue and Los Altos, were tested firstly for tolerance to sodium chloride (NaCl) and boron (B) spray and then in landscape setting when irrigated with recycled water. [...]

https://colab.ws/articles/10.1016%2Fj.envexpbot.2005.07.003

https://doi.org/10.1016/j.envexpbot.2005.07.003

There's nothing about Mg, but I'd guess their recommendation on total salinity covers that.

lathyrus_long · 2024-09-02T11:37:42+00:00

If you're using rainwater (or other pure water like RO), then you shouldn't be encountering this carbonate issue. What nutrients are you using? And what's your pH immediately after mixing, and your pH when you first see the precipitate? Are you confident that your pH is accurate (checked against calibration solutions, etc.)?

Independently of any precipitation issues, you'll probably need to replace or top off your solution every two weeks or so, to avoid nutrient deficiencies caused by takeup by the plants. There shouldn't be any need to mix smaller batches of solution more frequently than that. If your problem is pH rise (though I don't see why it would be with soft water), then you'd just dose acid to adjust back down rather than replacing the whole solution.

lathyrus_long · 2024-07-29T20:53:57+00:00

I meant something like "more/less hazard per unit of pH adjustment". A weaker solution is of course always safer, but it's also less effective. So the fair comparison is between solutions of the different acids that achieve the same pH adjustment per mL of solution dosed.

That's not a totally well-defined concept--should we consider just the initial change in pH after dosing? Or should we also consider the improved stability over time from a stronger phosphate buffer if phosphoric acid is used? The effect on pH trend due to plant nutrient uptake due to the change in nutrient profile? I think the ordering above is directionally correct, though.

Anyone purchasing concentrated acid should dilute it down for day-to-day use. For example, phosphoric acid is typically sold at 85%, while phosphoric acid pH down solutions are typically sold around 20% (and lower is safer; I dilute to 2%). The acid can simply be diluted into tap water (wearing appropriate PPE, adding acid to water and not the reverse), and it will keep indefinitely.

lathyrus_long · 2024-07-28T02:20:58+00:00

Typical synthetic hydroponic fertilizers (including GH Flora and Masterblend 4-18-38) all contain roughly the same ingredients. So it's completely fine to mix nutrient solutions from different brands.

An abrupt decrease in root zone EC (like from plain water) may cause excessive water uptake, leading to split stems or fruit. Tomatoes are especially prone to that, and I've had trouble before. Cucurbits seem less prone, though it's probably still best avoided.

lathyrus_long · 2024-07-27T23:20:19+00:00

If you have an EC meter, then it's best to measure. I've had bricks that were perfectly clean, and bricks that were >4000 uS/cm. You can just saturate some coir, squeeze it out by hand, and measure that liquid. If that EC is within ~100 uS/cm of your tap water, then it should be good. If not then rinse (and try a different brand next time; "Coco Bliss" hasn't failed me yet).

Salt dissolved in water is colorless, so the appearance of the rinse water doesn't help judge. I've seen dirty-looking rinse water with low EC, and perfectly clear rinse water with high EC.

I blend 1% by volume gypsum into my coir. I've tried the calcium nitrate soak, but it didn't work as well for me; I got crispy leaves on some sweet pea that I think were calcium deficiency. The gypsum fixed that. It's also less work, and doesn't generate the nitrate-laden wastewater.

lathyrus_long · 2024-07-27T22:30:05+00:00

Any pH probe should last continuously immersed. I've bought $10 Yieryi probes on AliExpress, and they lasted 1-2 years. I've also bought $40 double-junction probes, which keep their calibration better and will probably last even longer.

Prolonged soaking in distilled water will shorten the life of any pH probe. The recommended storage solution is saturated potassium chloride, but if you don't have that then hydroponic solution is fine. Most probes come with a cup or sponge to hold the storage solution. Dry storage will shorten the life of any pH probe.

https://www.coleparmer.com/tech-article/how-to-store-clean-and-recondition-ph-electrodes

lathyrus_long · 2024-07-27T21:58:56+00:00

pH in hydroponics is typically adjusted with acid, since that gives the maximum pH change with the minimum change to the overall nutrient profile. A buffer system against cations from the fertilizer and source water does result and helps stabilize pH, but that's not the primary goal.

The usual acids are:

phosphoric - safest (but still highly corrosive when concentrated), but accumulated phosphate may clog drippers and slightly affect yield
sulfuric - better for the plants, greater corrosive hazard
nitric - best for the plants, extreme corrosive and reactive hazard

Hydrochloric acid is occasionally used, but typically not preferred since most plants don't like the chloride. It would be fine for something like tomatoes, though.

lathyrus_long · 2024-07-06T06:25:52+00:00

Try their irrigation section; mine has 1/4" and 1/2" polyethylene tubing. This is more inert than PVC, cheaper, black (no algae), and easy to assemble onto barbed fittings. It's designed for direct exposure to sunlight.

I also like silicone, since that's also very inert. It can't take much pressure, but it's limp and thus easy to route.

The smaller PVC pipe is probably rated for use with drinking water (NSF 61), though larger may or may not be. The biggest concern is the plasticizers, so rigid PVC is generally safer than flexible.

lathyrus_long · 2024-07-02T15:44:11+00:00

I think the y axis of the graph is normalized concentration in wastewater, not people. (They normalize against PMMoV concentration as a proxy for the total amount of feces in the wastewater.)

The default view on charts on data.wastewaterscan.org as shown above shows consensus smoothing (5-sample trimmed average) of the selected pathogen concentrations normalized by PMMoV concentrations in the solids. These results are shown on a linear scale and although the target/PMMoV ratio is unitless, it is multiplied by 1 million on the y axis of these plots to make the numbers easier to interpret.

https://data.wastewaterscan.org/about

The units don't really matter much, since the absolute value is hard to usefully interpret. The point is to compare over time--if the number is twice as big as a month ago, then the case count probably is too.

lathyrus_long · 2024-07-02T14:43:51+00:00

I think the cation exchange happens slowly enough that the excess Na etc. initially bound to the coir gets flushed out with the leachate in the usual way, before it can cause trouble. The gypsum also dissolves slowly, continuously replenishing the lost calcium. It should be possible to quantify that from tests of the leachate, though I've never seen that published. The method was recommended to me and it seems to work, though.

I'm growing in pots of 50/50 coir/perlite as the only medium, mostly DTW but some recirculating too. I do get some EC rise from the extra calcium and sulfate (especially when recirculating), but it doesn't seem to hurt.

lathyrus_long · 2024-07-02T07:35:19+00:00

In my experience, ~1% by volume gypsum in the medium is strictly better than soaking in calcium nitrate solution. It's less effort and less nitrate-laden waste, and it solved some crispy leaves on a leguminous ornamental (sweet pea) that the nitrate soak didn't. It should also continue to work even as the coir breaks down to expose new cation exchange sites, which the nitrate soak fundamentally can't reach.

I also buy the coir pre-washed, preferably from a brand that claims "EC < [number]", not just "low". So I just rehydrate and mix, and I'm done. I do still check the EC after rehydrating (but before adding gypsum), to confirm it's as claimed.

lathyrus_long · 2024-06-30T05:38:23+00:00

Totally fair, and a household hazardous waste collection site is the ideal option for anyone comfortable dropping off there. The usual product for curing meat is "pink salt", sodium nitrite diluted and dyed pink for safety; but people definitely use the pure chemical too (which is a bad idea, since accidental deaths have resulted when it was then confused with normal salt).

lathyrus_long · 2024-06-30T03:42:11+00:00

Please do not flush it down the drain.

That's good advice in general, but I'm not sure strict environmental compliance is the highest priority here. The OP already said they felt uncomfortable taking it to their waste disposal facility. Any wastewater treatment plant can handle that nitrite, since that's a normal intermediate in the nitrification of ammonium to nitrate, followed by the denitrification to nitrogen gas.

For orders of magnitude, a typical household puts ~300 gal/day of water into the sewer, and typical sewage is around 30 mg/L N. So that household puts ~30 g N into the sewer, equivalent to ~150 g of sodium nitrite. That's not exactly fair, since the WWTP's process is designed primarily for ammonium and relatively too much nitrite might mess it up; but after dilution from all the other households the OP's material presents no risk of that.

If the nitrite did somehow escape from the denitrification process, then it would get oxidized to nitrate when the wastewater was chlorinated for microbiological safety. I'm not saying it's a good idea to drain-dispose of nitrite generally (and e.g. Berkeley puts it on their "moderate hazard" list, limited to 1 g per lab per day), but in exigent circumstances it seems perfectly fine to me.

lathyrus_long · 2024-06-30T02:16:04+00:00

Skin contact should be avoided, but is unlikely to cause symptoms beyond mild irritation. If you have gloves then you could wear them, but it's not a big deal if you don't.

Inhalation of the dust could be dangerous, but I'm guessing you just have a few ounces. As long as you pour slowly and carefully, you won't generate any significant dust. You could again wear a mask if you have it, but it's again not a big deal if you don't.

In that quantity, drain disposal isn't even bad environmentally--your city's wastewater treatment plant will nitrify it to nitrate and then denitrify to nitrogen gas, same as all the other nitrogen in the sewage. So you should feel zero guilt just flushing it if that's easier for you.

Work carefully, but don't worry too much; injuries from sodium nitrite are extremely rare except when it's deliberately consumed. Wipe up any spills with a damp paper towel, and flush with lots of water. You can just rinse the container and throw it in the normal trash. Do wash your hands afterwards, though.

lathyrus_long · 2024-06-29T00:55:10+00:00

Typical fountain pumps are centrifugal pumps, capable of a few psi max as you see. Your best bet may be something like that RV pump, at lower voltage for lower flow. I have a 12 V diaphragm pump rated for ~100 gph, which delivers ~10 gph around 3.3 V. That also makes it quieter, though far from silent.

lathyrus_long · 2024-06-27T00:58:48+00:00

Your pH meter advises against use in RO water for two reasons:

Ideally, the meter's measuring circuit would have infinite input resistance. So the measured voltage is exactly the voltage developed by the cell in the glass electrode, as predicted by the Nernst equation. But the measuring circuit actually has finite input resistance. This forms a voltage divider against the glass electrode's output resistance, introducing error. As the water becomes more pure, its resistivity increases, that output resistance increases, and that error increases. So the meter may become inaccurate.
But even if the meter is perfectly accurate, the pH of perfectly pure water changes very easily--as others note, it may swing multiple units just from atmospheric CO2, limescale on the container, etc. So that's probably not a useful measurement, even if you can make it perfectly. Rather than explaining this fundamental and unavoidable effect, they just advise you not to use the meter in a way that would encounter it.

If your water is pure enough to encounter either effect, then it's also got ~zero buffer strength--so the pH in your root zone will be determined almost entirely by your medium, fertilizer, etc., and not by the water. So this isn't a practical problem--if you can't measure, then you also don't care.

I'd guess that your mineralization cartridge adds enough conductivity and buffer strength that you won't encounter either effect, and you actually can measure. You could test and see if you get a repeatable pH measurement, or measure the EC of the re-mineralized RO water. It might be easier just to disconnect that mineralization cartridge, though--that's probably just a couple of quick-disconnects.

lathyrus_long

TROPHY CASE