Gone for borates

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Calcium phosphate scaling is a non-issue in pools. Phosphate levels are measured in parts-per-billion concentration and most pools will have levels below 2000ppb (2ppm). As long as a pool owner maintains calcium levels in the normal range, there simply isn’t enough calcium and phosphate ion concentrations to overcome the solubility limit. It’s takes very high pH, and very large concentrations of both calcium and phosphate to cause scaling. The pool industry has an unfortunate habit of promulgating all sorts of chemical theories to explain problems and then incorrectly uses and confuses correlation as causality. When one actually looks at the detailed scaling potential for calcium phosphate precipitation, it becomes immediately clear that it is least likely to happen in your pool.

Phosphates are a macronutrient for algal growth, that’s it. If you lower phosphate levels, you make it harder for algae to grow and you limit their growth rate. That’s it. Chlorine sanitizes water very quickly and algae can not effectively grow in properly chlorinated water. Thus, phosphate removal is more of an insurance policy, line using algaecides, than a sanitation strategy. If phosphates are high in a pool, remediation might be worthwhile, but it typically requires knowing why the PO4 levels are elevated in the first place. Otherwise, you could simply be shooting yourself in the foot constantly trying to battle back phosphates.
 
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Righto. Cool and cloudy day today, so the kids are not going to want to swim after school.

pH was 7.38. I just dumped 5kg of Boric acid in. In theory that'll take me to 46ppm and should drop the pH to 7.11 according to poolmath.

I've also mixed up a 50ppm 1L "standard" (In reality it'll be 50.7 +/- 1ppm, but who's really counting?). I just need some more DI water to make up the volume as it turns out the kids have been watering the garden with "daddys special water".

Meetings this morning, so let's see what happens when I get home this afternoon.
 
Will be interesting to see where your pH sits, actual compared to theoretical.

And thanks to Matt for commenting. Phosphates are irrelevant for both algae and phosphate calcium scaling in properly chlorinated pool water. And of cause there’s the direct link to the Mannitol test for borates in Matt’s signature. The Link I provided earlier was to the start of the thread.

New borate drop test at piscines-apollo vs. test strip
 
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Ok, pH is 7.21, so I assume some of the carbonate buffered that a bit. (Edit: and of course I put the hose in the pool to top it up between measurements, so that would have helped it up a little).

Borate test of my knock-up garage "standard" was somewhere between 12 & 13 drops (so between 48 & 52ppm). That's near enough to 50.7 +/- 1 to make me comfortable with my testing methodology.
Borate test of the pool was just about 11 drops (so 44). Theoretical based on water qty and added mass was 46.

So for never having done a borate test before, both tests come out "about right" and certainly "near enough for Glasgow" (to quote Billy).

I'm not unhappy with any of those results.

I picked up Mannitol e-bay. I had Bromothymol blue left over from a fish tank we got rid of 8 years ago, and the other reagents came from the CCL test kit.
Water sample was done with a 50ml volumetric pipette and the test done in a 100ml Erlenmeyer flask on the mag stirrer.

Piece of cake.
 
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pH up to 7.27 with an aerator on the return and a bit more fill water. Added another 1195g of Boric acid to bring the level up to a theoretical 55ppm.

I'll let it filter for another couple of hours and re-test.
 
I'm all excited for you.
I want to do the same!!
Except I've got year 12 chemistry knowledge from 1991, so forget about home testing, let alone creating my own standard solution!

Can't wait to hear about your benefits, real and perceived, of introducing Borates
 
yann said:
Except I've got year 12 chemistry knowledge from 1991, so forget about home testing, let alone creating my own standard solution!
Click to expand...

Shhhh. You and I did yr 12 chem the same year. If you promise not to tell anyone, I'll tell you a secret. None of this is rocket science.

To create my "standard solution" I took my 19kL pool in pool math and told it I wanted 50ppm borates using boric acid. It told me I needed 5433g of boric acid for 19,000L. So that's 0.286g for 1L. So I took a 1L volumetric flask and put 0.290g of boric acid in it, and topped it up to 1L. That's 50.7ppm and my scales are +/- .005g, so that's roughly +/- 1ppm. No magic, just a bit of maths.

As for the test, if you have the Clear Choice Labs kit, you can use the 25ml line on the TA or CH test (the high res line) and get 7ppm borate per drop, or you can use 2 of those 25ml measures in another container to get your 50mls. No measuring equipment required.

I already had the Bromothymol blue as it's a common pH indicator for fish tanks. You can buy it at bunnings. The only thing you won't already have is the mannitol, and that cost me $10 on e-bay.

Now sure, I already have a 1L volumetric flask, 50ml pipette, mag stirrer, beaker, flask and scales good to 5mg. But you don't *need* any of that.

My portable mag stirrer is an old 80mm computer fan with the blades cut off, a neodymium hard disk magnet araldited to the top and a PVC plumbing cap glued over it. Admittedly it's only good to 80C before the magnet loses its magnetism and the glue falls apart, but I've made a better version for use under a kambrook electric fry-pan for my "heated lab stirrer".

Again, no magic and nothing that can't be knocked up in the back shed. So if you want to give it a go, it's not difficult or complex.
 
Xylitol works too. I’ve used both and have gotten the same results. Xylitol is easily found online as it is used for people who wish to be on a ketogenic diet (“keto” diet). Just make sure whatever you get is 99% purity or better.
 
Yeah, I found a local source of Xylitol but only after I'd already received a 100g of Mannitol. So when that's done then I might switch over. 6 of 1, half a dozen of the other.

Test this morning was ~52ppm with a pH of 7.37, so I think it's all good. I can go back to just swimming in it rather than testing it.

I gave it a brush this morning and thought I saw a wisp of greeninsh/brownish dust come off the fiberglass where the gelcoat has lost its colour, so I'll need to keep an eye on that.
 

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Brad_C said:
Yeah, I found a local source of Xylitol but only after I'd already received a 100g of Mannitol. So when that's done then I might switch over. 6 of 1, half a dozen of the other.
Click to expand...

For $10, stick with the Mannitol. I found the Xylitol first, wasn’t sure it would work but it did. Then I found the mannitol on ebay and now I have a life time supply of both. Not sure I’m capable of doing the ketogenic diet, does that involve giving up beer? :cheers:
 
We all had a swim this arvo. Wife commented the water tastes different. Not good, not bad, just different. She's right, I tasted it too. Definitely a different look to the water. A bit like oil poured on it. Smoother, less ripple. Quite bizarre to be honest for only 50ppm of a chemical. I can't say it made a noticeable difference to the feel, but I wasn't in very long and most of that was chucking the kids around.

I'll have to take some samples and compare with tap water to see if there is any measurable meniscus difference.

It'll be interesting over the next week to see if it makes a difference to the youngest sons eczema.
 
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Right. 3 weeks in.

pH stability has been a...maz..ing. I started with 7.3. It's now up to 7.6 and there has been 3 "weekly" top ups since then. My calculations indicate I put 600-1000L in per week to account for evaporation. With my fill water, 1000L adds ~7.3 to the TA and about 4.7 to the CH and the pH is ~8. Testing CH over a couple of months indicates that's not out of the ballpark.

Chlorine demand dropped about 0.5ppm / day which allowed me to wind the chlorinator back. That's come up again the the last couple of days as we are starting to get a lot more organic matter in the pool as the trees start to moult. So not a significant change, but noticeable enough that I had to adjust a knob to get the FC down below 10.

I can still taste it, but after 35 odd years of Salt pools (and 20 of those are with this pool) it'll take more than 3 weeks to become "normal". No significant change to the eczema on the little guy, but then the weather has turned and we're in the pool less frequently.

Did I mention the pH stability? I've *never* gone more than 2 weeks without adding acid, even if it's only ~100ml. 0.3 pH points in 3 weeks even after top ups with no acid is awesome.
 
Swimming season is now upon us. Did a borate test tonight and it was down to ~24ppm, so + 3.5kg of Boric acid to bring it back up to ~55.

We got quite a bit of rain over winter and the pool has a strategic leak high up in the skimmer that I've not fixed as is saves me from having to worry about draining water unless it has been torrential. 2 good backwashes since March also, but to drop ~20ppm of borate would indicate we'd lost nearly 10,000L of water over winter. That's half the pool contents.

I tested twice, and also tested my 50.7ppm standard and the tests all came out good.

Come to think of it, I've had to add about 30kg of salt too and that's 3/8ths of the total pool requirement.

Wow, that's a lot of water turnover. Oh well, forecast 40C tomorrow so I'm sure it'll get a workout.
 
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