Need some basic advice -TA, pH, CH, FC all things chemical

[JamesW]

The test is referred to as an “accelerated” test, which means that it is somehow faster than a normal “leave it outside for years” test.

You would need to read the actual test report for the details of what intensity of light was used and what the assumptions and conclusions were.

It might have been done at 1 x Sun or 2 X or 3 X.

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[JamesW]

You also have to know what location the "Sun" is being simulated for.

For example, Phoenix has about 1,000,000 X* more UV than Boston.

*Estimated.

 

[newdude]

The test is referred to as an “accelerated” test, which means that it is somehow faster than a normal “leave it outside for years” test.

I am always skeptical about those as alot can happen randomly during the slow process that might not happen in the quick test.

Like when they test new suspension/tire setup 'over a million miles' on a concept car. Rapidly hitting speedbumps on a treadmill is not the same as hitting varying potholes over 10 years because the steering wheel was turned for some of them, hitting the side wall and not the meat of the tire.

Lots of YMMV there.

 

[mgtfp]

Like when they test new suspension/tire setup 'over a million miles' on a concept car. Rapidly hitting speedbumps on a treadmill is not the same as hitting varying potholes over 10 years because the steering wheel was turned for some of them, hitting the side wall and not the meat of the tire.

Accelerated testing is tricky. You have to make assumptions and understand the physics/chemistry behind your failure modes. Then apply models to tell you by how much you have to increase your load (like light intensity, temperature, temperature change, vibration amplitude/frequency, etc) to "achieve" the same degradation in a few weeks/days that you would get over 10 or 15 years under normal conditions.

And then remember that the acceleration was specific to a particular failure mode with a specific lifetime model. Other failure modes might get under- or over-tested or not tested at all under the chosen conditions and test duration.

There is no one-fits-all accelerated test that simulates a realistic fast-forward for everything that could happen.

But what's the alternative? Have hundreds/thousands of cars being driven for 10-15 years by different drivers (commuter, Sunday driver, Taxi driver, stay at home parent, etc) in different environments (very hot, very cold, moderate, hot humid, cold humid, etc), combinations of these when a car gets sold e.g. from driver A in Phoenix to driver B in Anchorage, etc etc etc. Development times (and sales prices) would explode if you had to add 10 to 15 years of reliability testing to the rest of the development process.

Or not test at all. Like in the good old days, when we thought it was a good idea to add radioactive materials to toothpaste:

Doramad Radioactive Toothpaste (ca. 1940-1945)

 

[newdude]

But what's the alternative? Have hundreds/thousands of cars being driven for 10-15 years by different drivers

Certainly not. Was just pointing out the inherit flaws of accelerated testing.

 

[mgtfp]

Was just pointing out the inherit flaws of accelerated testing

I know, just being devil's advocate...

There are certainly flaws. And it can be very frustrating to explain to someone with no technical background why a certain failure is not covered by all the tests being done, and why another test is required.

 

[JoyfulNoise]

Or not test at all. Like in the good old days, when we thought it was a good idea to add radioactive materials to toothpaste:

Doramad Radioactive Toothpaste (ca. 1940-1945)

I fail to see how that’s not a good idea …

 

[Orion7319]

I fail to see how that’s not a good idea …

I mean everybody has those mornings when ya just gotta nuke that halitosis….

 

[JamesW]

A wide range of radioactive products were sold as cure-alls, primarily from the 1920s to the 1950s.

Radium-containing pills, pads, solutions, kinds of toothpaste, and devices designed to add radon to drinking water were once commonplace.

Older camera lenses from the 1950s to 1970s often used coatings of thorium-232 to alter the index of refraction.

Ceramic materials such as tiles or pottery often contain elevated levels of naturally occurring uranium, thorium, or potassium.

Shine a UV light on old ceramics to see if they glow.

Brazil nuts contain high levels of radium-226 and potassium-40.

Bananas containing enough radioactive potassium-40 have occasionally set off alarms at border crossings and ports.

Early 19th-century European glassmakers sometimes added small amounts of uranium to the glass to give it a yellow or greenish color.

Some watches and clocks contain a small quantity of hydrogen-3 (tritium) or promethium-147 as a light source.

Some older (pre-1970) watches and clocks used radium-226 to illuminate the dials and numbers.

Shoe-fitting fluoroscopes in shoe stores would use X-rays to see how well shoes fit.

Let's not forget about things like lead and asbestos which were added to almost everything.

 

[SoDel]

The stuff in the standards doc seems consistent with a “hunch” I had that UV has more to do with faded potato chip liners than Cl. Still just a hunch but at least the data so far doesn’t eliminate it from the matrix lol.

 

[SoDel]

I think it started with anecdotal evidence that higher CYA seemed to provide better chlorine protection than you would expect from the amount of chlorine bound to CYA. In the Pool Water Chemistry sticky thread, Richard refers to a member from the Poolforum (a lot of the content in that thread, Richard originally posted there and copied it over to TFP - you won't find a member called Aylad on TFP, maybe Janet is here under a different user name):



Later in that post, Richard lists theories to explain this. The general idea is that CYA doesn't just protect chlorine that is bound to it, but that by absorbing UV light, CYA in the higher water layers also provides additional protection for chlorine (even if not bound to CYA) in the lower water layers.

The main breakthrough came, when Mark (@mas985) did experiments that gave empirical evidence for the better UV-protection at higher CYA levels. A lot of that is happening all along that Pool Water Chemistry sticky thread. It's really worth going all the way through that thread. Richard kept referring to Mark's experiments over the years, for example in 2015 here (with links to Mark's experiments from 2007):




Quite recently, Mark did more experiments:

I’m starting to wonder if the reason one can still get effective sanitation with the SWG despite low FC / CYA ratios is the “secondary sanitation“ system effect of the water passing through the SWG cell and on down the return pipe with the Cl gas, etc., thus killing everything in the water as it passes through. If this is the case, then residual chlorination could be inadequate at very low FC / CYA ratios. Do you know if anyone has looked at that and any conclusions?

If the UV protection theory explained it, it doesn’t answer the question of what about constant pool circulation throughout the day or why do low FC / CYA ratios only seem to work in SWG pools.

What do you think?

 

[mgtfp]

There are two different things here.

One is that higher CYA provides better UV protection, which is SWG independent. But only with a SWG it's worth taking the risk of more difficult slamming should something go wrong and take the benefits of better UV protection.


The other one is that you can run a lower FC/CYA ratio with a SWG, which effectively means that you can run a similar FC at a higher CYA.

I personally have noticed that I can't go much below the "normal" target FC. I don't see algae or fail OCLTs, but I get backswimmers, which can be a sign that there is algae lurking somewhere. FC 8-9 ppm at CYA 80 ppm seems to work well for me. If it goes below 7ppm, I start to notice more backswimmers.

My SWG (like most Aussie models) adjusts chlorine output by regulating the cell current rather than by duty cycling (i.e. cycling between 100% and 0% to get the required average over time). Maybe that plays a role, and could indicate that higher FC in the cell helps to keep FC in the bulk water lower. Don't know.

I once took a sample with a syringe out of the return line while running the SWG on 100%, and FC was about 3ppm higher than the bulk water FC (in the meantime I got a new, larger SWG, and I guess I'd test more like 4pmm with that one). FC is certainly elevated in the cell, but it's not like you are constantly slamming. In my normal SWG operation, FC would only be about 1-2ppm elevated in the return line.

Maybe it's more the constant chlorination, or just the lower risk of ever falling too low that allows lower FC/CYA.

Maybe there is something else.

In the end, everyone needs to find out what works for them. If in doubt, go rather higher than lower.

That the FC/CYA ratio is the relevant parameter, has a solid scientific background. Which exact ratio is required to keep a pool free of algae, has more of an empirical background, I'd say.

 

[SoDel]

I personally have noticed that I can't go much below the "normal" target FC. I don't see algae or fail OCLTs, but I get backswimmers, which can be a sign that there is algae lurking somewhere. FC 8-9 ppm at CYA 80 ppm seems to work well for me. If it goes below 7ppm, I start to notice more backswimmers.

That’s consistent with what I can discover on the “science” end — FC about 10% of CYA is effective, non-irritating and provides even a bit of a safety factor for pathogens and algae.

That the FC/CYA ratio is the relevant parameter, has a solid scientific background. Which exact ratio is required to keep a pool free of algae, has more of an empirical background, I'd say.

That’s where I stutter. The whole “The Chart” thing, especially for for salt gives me the heebie jeebies. It works, years of safe clean pools, yup, just go the the algae green pool thread. Falk and O’Brien came up with a methodology to (from what I can determine) calculate the equilibrium level of HOCL vs OCL vs chlorinated isocyanurates, as a practical matter independent of pH (at sensible levels) for a given FC / CYA. We need a minimum level of HOCL to be sure to kill the nasties (I think that’s where there could be a debate? What level of HOCL is really required when the OCL and chlorinated isocyanurates will be converted to HOCL to maintain equilibrium thus ensuring a contact time with HOCL). But the calculated HOCL for a given FC / CYA “should” not be open to empirical methods, no? And the standard seems to be 0.05 ppm HOCL as a floor.

 

[mgtfp]

But the calculated HOCL for a given FC / CYA “should” not be open to empirical methods, no?

The HOCl concentration depending on FC, CYA and pH is "fixed" by science, nothing empirical there. That same calculation also shows that, within pool relevant ranges, HOCl is proportional to the FC/CYA ratio, and therefore FC/CYA is a good proxy for HOCl that is measurable with test kits, rather than expensive test equipment.

But which HOCl level (or equivalently which FC/CYA ratio) is required to keep a pool free of algae (trouble free), will need a bit more empirical experience, I think. Which exact FC/CYA is required, might also depend on other parameters, like hiding spots for algae in liner folds, pool cleaners, skimmer weirs, rough plaster, amount of brushing, etc, or even phosphate levels (should they be very high - not what pool stores consider high).

The table is scientific it the sense that all combinations of FC and CYA that result in the same FC/CYA ratio are equivalent because they result in the same HOCl concentration (within a margin for rounding to integer values for FC). The exact HOCl level to keep algae in check requires some experience.

I'd say that the liquid chlorine chart should work universally for most pools. Ideally, SWGs should allow lower levels, but that doesn't always seem to work. Many seem to treat the SWG-target more like a min-value and aim to always stay above it, and that seems to work well for most.

As mentioned before, I seem to be able to go down to the SWG-min without failing the OCLT, but I notice backswimmers. Maintaining FC around 10% of CYA seems to be more trouble free for me. But occasionally slipping down to 5% doesn't seem to end in a disaster either. In that sense, it seems to be a min value for me, but not a value where I would run my pool permanently.

Maybe it's not a coincidence that the liquid chlorine min is more or less the SWG-target.

 

[SoDel]

But which HOCl level (or equivalently which FC/CYA ratio) is required to keep a pool free of algae (trouble free), will need a bit more empirical experience, I think. Which exact FC/CYA is required, might also depend on other parameters, like hiding spots for algae in liner folds, pool cleaners, skimmer weirs, rough plaster, amount of brushing, etc, or even phosphate levels (should they be very high - not what pool stores consider high).

. . . The exact HOCl level to keep algae in check requires some experience.
.

That makes perfect sense.

But maybe “The Chart” should include a footnote explaining this. Maybe another footnote that if the values don’t seem to be doing the business, bump by x% at a time up to y before assuming the need for inevitable serial
SLAMs every time a particular pool gets its inevitable blooms. Been here a short time but noticed there seem to be a lot of “have algae, help me“ threads from folks who say they are following along.

I got a reaction for suggesting that HOCL levels (approximated based on Falk) might be too low to prevent algae for a poster that had an inexplicable algae bloom despite following “The Chart.” My post was deleted. Was gently told not to post anything more on pool chemistry. Was also told that everyone can have confidence that “The Chart” works, nothing to see here. Whatevs. That didn’t make sense.

 

[tim5055]

Been here a short time but noticed there seem to be a lot of “have algae, help me“ threads from folks who say they are following along.

Been here a long time and the folks who have issues over and over once they answer questions seem to not be following the program.

Sadly we have become a instant gratification society. They want an executive summary. They don't want to read the articles, let alone footnotes.

Stick around for a few years, learn the program and follow it, don't try to change it with less than a month under your belt.

I'll be perfectly honest, one or two folks show up each year who are smart, understand the science and think they can do better. Most don't last.

 

[SoDel]

Not trying to change it. At this point, just to understand what it is, what it does, and does not do. The deep end seems to be the place to contemplate the what ifs and why and why nots. I’ll pretty much stick here for a good while. Will lurk from afar in the elsewhere and learn as much as I can.

I will say I started knowing literally nothing about pools and my pool is so clear right now it’s hard to see where the waterline is. So your methods are doing something right to say the least. But there’s clearly more to it than the executive summary so into the deep we go . . .

 

[Bperry]

Not trying to change it. At this point, just to understand what it is, what it does, and does not do. The deep end seems to be the place to contemplate the what ifs and why and why nots. I’ll pretty much stick here for a good while. Will lurk from afar in the elsewhere and learn as much as I can.

I will say I started knowing literally nothing about pools and my pool is so clear right now it’s hard to see where the waterline is. So your methods are doing something right to say the least. But there’s clearly more to it than the executive summary so into the deep we go . . .

I’ve been around for a couple years and can’t recall anyone who follows the TFP method getting algae, with the exception of maybe one or two. I’m sure there must be more though.

It’s usually easy to tell when they aren’t following even though they say they are. When they report a FC of 2.41ppm using strips and any kind of value for a TC, I can tell something is off.

 

[SoDel]

I’ve been around for a couple years and can’t recall anyone who follows the TFP method getting algae, with the exception of maybe one or two. I’m sure there must be more though.

It’s usually easy to tell when they aren’t following even though they say they are. When they report a FC of 2.41ppm using strips and any kind of value for a TC, I can tell something is off.

I’m thinking of this thread in particular, as one example but I haven’t followed it closely so maybe the guy didn’t do what he should. SWG, FC 6, CYA 70, no bueno. Approximated HOCL would be less than 0.03 ppm. Here’s the thread (if I got the link right lol). Algae bloom and not sure why.

But it’s not my intention to make some sort of case that “The Chart” works or doesn’t, just that it may not work all the time, the SWG numbers don’t square, and examining the particulars when something goes wrong is worth the effort just to understand what’s (possibly) going on. Just my (admittedly uninformed) opinion that telling the guy to keep brushing and slamming and examining every nook and cranny (including it seems places sunlight does not reach) for ordinary algae might not be what the issue is. Or maybe it is. But the HOCL level also seems to tell a story. Would it cause pain to anyone to tell the guy to maintain his FC at around 8 minimum with his 70 CYA going forward and it likely won’t happen again?

Anyway, it provided food for thought to generate the questions, what kills algae (seems to be 0.05 ppm HOCL as an agreed level for kill); how does all this HOCL and OCL and chlorinated isocyanurates relate to each other in water (equilibrium levels at a given FC / CYA ratio with a timy dash of pH just to complicate it a bit), etc.; what level of FC is dangerous or uncomfortable to people (less than 10 ppm is ok (but don’t drink lots of it) with no CYA, mamy times that with CYA so up to 10 ppm with nominal level of CYA works for me until I can look into that a bit more.

Were it not for that thread and this thread, there’s no way I’d understand or have reason to contemplate any of that so TFP gets applause from me.

edit: and here is a different approach that makes sense (and maybe I have to eat some of my words): Time to slam again? I see advice to run FC “hot” and depart upwardly from The Chart values when it seems sensible to do so.

 

[Bperry]

I’m thinking of this thread in particular, as one example but I haven’t followed it closely so maybe the guy didn’t do what he should. SWG, FC 6, CYA 70, no bueno. Approximated HOCL would be less than 0.03 ppm. Here’s the thread (if I got the link right lol). Algae bloom and not sure why.

A couple of things I noticed in that thread.

There are no pool math logs (or paper equivalent) to be able to see all the water parameters at once. It’s not a personal critique, but he spent a lot of time writing down irrelevant details when all that was needed was actual test results over a period of time.

He started a SLAM and finished it 48 hours later during an active algae bloom. I’ve never heard reports here of a pool going from green to clean in only 48 hours. So it’s pretty easy to surmise that the SLAM wasn’t done yet based on that alone, but we don’t know for sure because there’s no data to review to know if SLAM FC level was reached, and what the results of the OCLT were. Maybe all three criteria were passing, but we just don’t know.

A friendly note about all that is to not make it so hard. Just write down the test results and the date/time (or log stuff in pool math) along with what was added when.