extreme TA drop, is this even possible?

[mknauss]

I can guarantee the WG is not measuring at a higher precision. It is a test strip.

pH can move around based on chemical additions, aeration, fill water, excretions from swimmers, etc.

TA of 60 should be good. Your fill water will add TA. When you add acid, only lower pH to 7.6.

You should never have to add baking soda and acid. If you are, you have too much aeration or are lowering your pH too far when it reaches 8+.

 

[crackers8199]

You should never have to add baking soda and acid. If you are, you have too much aeration or are lowering your pH too far when it reaches 8+.

this confuses me, though. won't i eventually have to add acid to bring the pH back down? won't that also lower the TA (and eventually push it outside the range we're aiming for, requiring baking soda to bring it back up)?

 

[mknauss]

The TA can go down to 50 without issue.
See what happens as your pH rises. When it gets to 8, test the TA. It is likely that your fill water additions due to evaporation have raised your TA by 10 or more points by then.

 

[crackers8199]

The TA can go down to 50 without issue.
See what happens as your pH rises. When it gets to 8, test the TA. It is likely that your fill water additions due to evaporation have raised your TA by 10 or more points by then.

okay. so basically what you're saying is that right now (absent any significant fill water additions) i should remain pretty stable where i'm at?

 

[mknauss]

Sure. But in Lake Elsinore you have significant evaporation. So you are adding fill water. I suspect 30+ gallons per day. And I suspect it is most likely Colorado River water, with a TA of 130 ppm.

So monitor your pH. Test your TA when your pH reaches 8.

 

[crackers8199]

Sure. But in Lake Elsinore you have significant evaporation. So you are adding fill water. I suspect 30+ gallons per day. And I suspect it is most likely Colorado River water, with a TA of 130 ppm.

So monitor your pH. Test your TA when your pH reaches 8.

copy that. i actually just added water today (last time before today was saturday, but i actually over-filled a bit saturday so it took a while to come back down).

 

[mgtfp]

Looks like you're on a good way, well done! Pool store bills will soon be a faint memory of the past

There will always be some fluctuations. The whole chlorination cycle is pH stable, but depending on the time within this cycle you might still see some fluctuations. Just after a heavy swimmer load your chlorine has some work to do, that might bring pH down a bit until the chlorinator replaced the lost chlorine. Unless that swimmer load also brings a lot of splashing and aeration, that will let pH drift up.

Some chemicals like CYA will lower pH, consider that when adding, check the resulting pH change with PoolMath first.

A heavy rainstorm might bring a lot of aeration and drive pH up. And so on...

And try not to overshoot when adding acid, the lower the pH, the faster it rises back up. Thinking to bring it as low as possible so you have longer until it reaches your upper limit again, is a false economy.

Ideally, you just add enough to compensate the added TA from your fill water, and to keep your CSI where it needs to be.

Some people manage to find that sweet spot with more or less stable pH. That's not always possible, but you can at least minimise adding chemicals. Especially compared to pool store advice.

 

[crackers8199]

Looks like you're on a good way, well done! Pool store bills will soon be a faint memory of the past

There will always be some fluctuations. The whole chlorination cycle is pH stable, but depending on the time within this cycle you might still see some fluctuations. Just after a heavy swimmer load your chlorine has some work to do, that might bring pH down a bit until the chlorinator replaced the lost chlorine. Unless that swimmer load also brings a lot of splashing and aeration, that will let pH drift up.

Some chemicals like CYA will lower pH, consider that when adding, check the resulting pH change with PoolMath first.

A heavy rainstorm might bring a lot of aeration and drive pH up. And so on...

And try not to overshoot when adding acid, the lower the pH, the faster it rises back up. Thinking to bring it as low as possible so you have longer until it reaches your upper limit again, is a false economy.

Ideally, you just add enough to compensate the added TA from your fill water, and to keep your CSI where it needs to be.

Some people manage to find that sweet spot with more or less stable pH. That's not always possible, but you can at least minimise adding chemicals. Especially compared to pool store advice.

thanks! i'm surprised how much i've actually enjoyed figuring this all out, i thought it would be a bother and annoy the heck out of me very quickly but it really hasn't.

it seems like my current CYA level of 60 is not recommended for SWG (based on the chlorine CYA chart), i know we had talked about adding some earlier in this thread - should i consider adding now to get myself up to 70 or leave it as is for right now and see how this shakes out after a week or two of testing? my next weekly test will be saturday, i intend to do the full battery of tests every saturday (just did friday last week since i had just received the kit and wanted to get at it)...

 

[mgtfp]

None of these rules are hard and fast. They are designed to work for a large number of pool setups. Try it out. You can certainly operate a salt pool at CYA 60. If it's the optimum for your pool, is another question. Try 60 for a while and then try 80 for a while. Then compare how long you have to run the chlorinator, what happens with pH and TA and so on. It's important that your pool is stable and that you have understood what's going on in your pool, before you venture into fine tuning such details. Just try out what works for you if you enjoy this process of understanding your pool. If you are just interested in having a trouble free pool without having to think too much about it, then just stick to the TFP recommendations, they will certainly work.

I really only stick to the recommended CYA levels during the hottest times of the year, then I let it drift down again. I keep the pool open all year. Don't use it in winter but I don't like looking at a leaf dump all year. I don't need CYA 80 in winter, it would actually be counter productive because at lower temperatures, CYA binds more chlorine. We never get snow here, my SWG is able to operate all year round, I figure it's easier to just keep the pool running in low maintenance mode than having to deal with a massive clean up task in spring.

So, I make sure I have enough CYA from Christmas (that's an Aussie Christmas...) until about mid March. From April/May on, CYA get's diluted pretty quickly by rain. Currently I am keeping it at about 30. I could let it go lower, but it's hard to measure below 30 and I don't want to over-chlorinate because my CYA is lower than I think. I keep my FC above the fresh-water target over winter, the cell is hardly running compared to summer. Once we start getting the first nice days in September, I will slowly start getting the CYA level up again, and towards October/November I can hopefully have the first very refreshing dips again.

 

[crackers8199]

@mknauss @mgtfp did my weekly tests today, only number that really noticeably changed was the CYA. i did add some acid yesterday, and did a decent job this time of not overshooting. also, finally got my salt kit and measured the salt at 4200.

FC: 6
CC: 0
PH: 7.5
TA: 60
CH: 1250
CYA: 50
Temp: 79.8
Salt: 4200
CSI: 0.08

should i be thinking about adding CYA now to bring that number up, and if so what should i be aiming for?

 

[mknauss]

What was the CYA before? Do not make large changes in CYA based on one test. Has your FC loss per day gone up?
Sharing Poolmath logs lets us see your test data much easier.

 

[mgtfp]

CYA can take some time to show up in the test. Make sure to wait long enough before you test and that you gained enough confidence in interpreting it, this test is the trickiest one to get used to.

And never try to adjust CYA in one step. Add some and wait for the change to show up in the test. Then you'll know a lot better how much more to add to reach your target. You don't want to overshoot on CYA.

 

[crackers8199]

What was the CYA before? Do not make large changes in CYA based on one test. Has your FC loss per day gone up?
Sharing Poolmath logs lets us see your test data much easier.

CYA last test (the only other number i have, which was last weekend) was 60. although i guess since that was my first time doing the test, it is possible it was 50 last week too and i just lost the dot earlier even though it was still visible.

FC loss hasn't been noticeable really. the K1000 always has it at 5, waterguru every morning has it in the 3.5-4.5 range (this is at the start of the pump run for the AM, during which the SWG is running from 6am-noon). DPD test last weekend had it at 6.5, today it was 6.

As for sharing PoolMath logs, I didn't know that was even possible. i've been logging on poollogger.com because i like the interface a little better, but i'll download pool math and take a look.

CYA can take some time to show up in the test. Make sure to wait long enough before you test and that you gained enough confidence in interpreting it, this test is the trickiest one to get used to.

And never try to adjust CYA in one step. Add some and wait for the change to show up in the test. Then you'll know a lot better how much more to add to reach your target. You don't want to overshoot on CYA.

yeah, like i said above i'm wondering if it was really 50 last week too and i just lost the dot early even though it was still visible...

i guess it can't hurt to grab some CYA granules while i'm at the pool store this week, since i'm just about out of acid and will have to make a trip over there at some point anyway. at least then i'll have them whenever i need to add.

 

[mgtfp]

i guess it can't hurt to grab some CYA granules while i'm at the pool store this week, since i'm just about out of acid and will have to make a trip over there at some point anyway. at least then i'll have them whenever i need to add.

Exactly, CYA doesn't go off, good to have at home. If you are not struggling to keep chlorine production up, then there's no rush.

 

[crackers8199]

just did my weekly test today, and noticed the TA has jumped to 80. is that normal, considering i haven't added acid yet this week? the past two weeks i've been adding acid on friday, but this week my pH has been pretty stable so i didn't need to add it yet (planning to add today, as i'm up at 7.8 today).

 

[mknauss]

Your fill water is high in TA. You are adding fill water all week I would suspect. That will raise your TA.

 

[crackers8199]

Your fill water is high in TA. You are adding fill water all week I would suspect. That will raise your TA.

makes sense. after i added acid just now i re-ran all tests and TA was back down to 60. i hope i'm doing these right...

 

[mknauss]

That is a really large drop in TA for an acid addition. I suspect some test error.

 

[mgtfp]

How much acid did you add? TA going down to 60 from 80 seems to be a bit much to be explained just be adding acid. Even if you added enough to get pH from 7.8 to 7.2, TA should drop by less than 10. Some of that drop might just be explained by the test tolerances, maybe you were more like 75 (with test showing 80) before, and more like 65 (with test showing 60) after adding acid.

There are also some systematic errors that can happen, like that one here:

Sometimes a static electric charge can build up on the R-0009 dropper bottle tip, causing the drops to be smaller than usual and making the test read higher than actual. You can prevent this by whipping the tip of the dropper bottle with a damp cloth or tissue before you start and after each drop.

More details here:

Total Alkalinity

A drop-based test used to measure the alkalinity in water. Alkalinity helps serve as a … Read more…

www.troublefreepool.com

 

[crackers8199]

Even if you added enough to get pH from 7.8 to 7.2

that much. i was so annoyed with myself when i retested pH and saw it was down to 7.2...i tried to just add the same amount i added last week, which took me from 7.8 to 7.5 (exactly where i wanted to be), but obviously i way overshot again today.

Sometimes a static electric charge can build up on the R-0009 dropper bottle tip, causing the drops to be smaller than usual and making the test read higher than actual. You can prevent this by whipping the tip of the dropper bottle with a damp cloth or tissue before you start and after each drop.

i thought i had read somewhere that you only had to do that for the first few tests with the new kit, and then you could stop. is that not correct?