CH Test Question

[DONNIE]

I have adjusted my CH a little high. Should I worry? When doing the CH test I am adding 3 drops R0012 before the test and including those drops in my endpoint but am still getting blue with red specs. Is that OK? Knowing I am looking for 30+ drops can I add 10 drops at a time before swirling or do I need to swirl after each drop? Same question for the other tests. Pool looks great!!


Temp 43 (Waaaaaaa)
Ph 7.5
FC 6.0
CC 0
CYA 75
CH 420
TA 110
Salt 3500


Donnie

[chem geek]

Your CH is fine. In fact, you need a higher CH in a salt pool both due to the higher TDS, but also due to the fact that with the higher CYA your TA is composed of less carbonate alkalinity (also, you may want to lower your TA to 100 or 90 at some point if you find that you are fighting rising pH and adding acid frequently). So your 420 ppm level is great.

Normally, when the temperature drops, the pH will rise, so I am a bit surprised that you are at 7.5 pH. If you started there at 80 or so degrees, then you should be at around 7.7 or 7.8 now. That would have your water be a little less corrosive than it currently is -- not a big deal, especially with lower temps, but just letting you know that you could increase your pH if you want and it should find it's way back down again as the temps come back up in the spring. If you don't have a cover, then maybe your pH is slowly rising anyway so you can just let it do that if you want.

As for the CH and other tests, though ideally you add drops and mix simultaneously, I have not found any problem just adding a whole bunch of drops and then mixing, especially in the beginning when you know that you will be needing to add a lot. As for the mixed endpoint you are seeing, it should be blue overall, not with specs of red. Typically, adding drops in the beginning (before you add the calcium buffer and that you count in your final count of drops) is to prevent a "fading endpoint" which looks more like something that is blue that then turns back into red after a few seconds. So I'm not sure what these red "specks" are that you talk about. You can try adding more drops in the beginning to see if that helps.

With your CH level, you can also use the 10 ml sample size instead of 25 ml and then multiply your drop count by 25 instead of 10 (you use 10 drops of calcium buffer instead of 20 and 3 drops of indicator instead of 5). Not quite as accurate, but for the CH test, this really doesn't matter much as a change of 25 is not very large at the levels we deal with in a pool.

Richard

[DONNIE]

Thanks Richard. I was hoping you would see my post. My original fill was last month and about 50F. I have tried to keep my Ph at 7.5 but it wants to climb to 7.7 - 7.8 every 2 days. 7oz of muriatic acid every 48 hours seems to keep it at 7.5. I have been afraid to let it rise any higher as the water is beautiful.

Donnie

[DONNIE]

I do not have a cover by the way. As far as the red specks, they are exactly that. When it first starts from red to blue they appear. I have even added as much as 3 more drops with no further change to blue but the red specks remain.

From a search:

"One other thing-was this an error on my part or is this supposed to happen? When testing the Cal, there was a precipitate the same color as the water, just darker, swirling around the test container."
"This is normal. The first reagent in this test causes the magnesium in the water to precipitate out as magnesium hydroxide so you can get an accurate calcium hardness reading. The purple specks you are seing in the water is the magnesium hydroxide. The color of the water should be a definite blue. If it is still purple then you have not reached endpoint on this test. Keep adding drops and swirling until you get no more color change on adding a drop and don't count that last drop."

"Re- calcium hardness test. You win this one, the test is not complete until the color change is permanent. Those little purple specks in the water aren't the endpoint, you may have to add 10+ more drops to get the entire sample to change to the end color (the higher the reading, the more 'in between' drops there are - for both CH and TA)"

Donnie

[chem geek]

Cool. There are a lot of smart posters and useful information on this board. My water is probably not very hard so the initial fill probably didn't add a lot of magnesium so I don't see the specs that you do. It's nice to know they aren't a problem.

As for you pH rise, you can not only lower your TA to 90, but you can also add 50 ppm Borates as discussed in this thread. The combination of lower TA and having Borates seems to really do the trick. The lower TA means the pool is less carbonated so outgasses less carbon dioxide while the Borates are an additional pH buffer and are also an algaecide that lets you cut down your SWG production (since less chlorine gets used up killing algae) which lowers the hydrogen gas bubble aeration which lowers carbon dioxide outgassing. The pH rise is mostly due to carbon dioxide outgassing.

Richard

[DONNIE]

Richard, Is adding 7oz acid every 48 hours too much? Also.....after reading Waterbears borate thread it seems to add borates will increase my Ph so I add more acid to decrease Ph initally then it should stabilize and quit rising from 7.5 tp 7.7 every 2 days. I can't imagine trying to hold my Ph any lower.

Donnie