After almost 10 years using an undersized cartridge filter, I installed a big sand filter last June. Love the beast, EXCEPT for two things. Ever since then, pool water has been noticeably cloudy and I CANNOT get my TA & Ph under control. Since it's winter time, thought I'd worry about the cloudiness in the spring and focus on getting my chemistry stabilized. Wild fluctuations in both TA & Ph. For example, yesterday morning I measure the Ph - it's off the charts high. Blood red on the color chart. TA is VERY (~20) compared to last weekend. I like to get my Ph in range before I tackle the TA, so I add a 1/2 gallon of muratic acid. Remeasure the Ph in the afternoon and it's still a little high, TA still very low, so I add another 1/4 gallon of muratic acid and let it sit over night. Get up this morning and Ph is REALLY low (like maybe 6.7) and TA like 10. So I add about 12 pounds of baking soda. 4 hours later, TA is at 60 but Ph is sky high again - same blood red on the color chart. I've repeated this cycle about twice a month since I got the sand filter. Chlorine and CA are rock solid (~ 4.5 and 40 respectively). Any suggestions?
TA / Ph Roller coaster
- Thread starter hillyjd
- Start date
Low TA will result in quick pH swings. Try keeping the TA at 60 or higher while you bring down the pH. (Add baking soda to raise TA, wait an hour, add muriatic acid to lower pH which of course will lower TA, too.)
Does the TA appear to be dropping without you adding acid? Or do the acid additions explain the low TA?
Does the TA appear to be dropping without you adding acid? Or do the acid additions explain the low TA?
Your SWG will raise pH over time. You will need to raise the TA higher than normal so you have room to lower the pH and have both values in range. Raise the TA to around 120 then lower the pH to 7.5 When you are finished the TA should be between 70-120. Try not to let the TA drop below 70. Most pools have a TA they "like" that keeps the pH fairly stable. Once you get the TA back up it will be easier to find the best TA for your pool. Use the poolmath button to calculate how much baking soda and MA to add for each adjustment.
For an SWG pool, you usually need the TA on the low side so around 70 ppm. If you have it higher, then the rate of pH rise will be faster. When you add acid, it lowers both pH and TA, but for the TA to drop as much as you indicate you must be adding a lot of acid. 41 fluid ounces of full-strength Muriatic Acid (31.45% Hydrochloric Acid) in 16,000 gallons would drop the TA by 10 ppm, but starting at 70 ppm the pH would drop from 8.0 to 7.13. Also note that you'll use more acid more frequently if you try and keep the pH lower -- try a 7.8 target instead of 7.5 and don't lower the pH so much when you do add acid. That is, see how your pool does with a TA of 70 ppm and a pH of 7.8. Does it rise in pH as quickly? Do you use as much acid to maintain it?
Some people add 50 ppm Borates to their pool to reduce the frequency of acid addition. The borates buffer the pH without having the side effect of carbon dioxide outgassing that causes the pH to rise (the bicarbonate that comprises of most of TA outgases carbon dioxide causing the pH to rise). Do you have a lot of aeration sources in your pool such as waterfalls, spillovers, fountains, etc.? If so, see if you can reduce their on-time if possible.
I'm not sure why switching to a sand filter caused this problem -- that part doesn't make much sense.
Some people add 50 ppm Borates to their pool to reduce the frequency of acid addition. The borates buffer the pH without having the side effect of carbon dioxide outgassing that causes the pH to rise (the bicarbonate that comprises of most of TA outgases carbon dioxide causing the pH to rise). Do you have a lot of aeration sources in your pool such as waterfalls, spillovers, fountains, etc.? If so, see if you can reduce their on-time if possible.
I'm not sure why switching to a sand filter caused this problem -- that part doesn't make much sense.
Wow - thanks for all the great advice. Let me try and answer the questions. First - it does not look to me like the TA varies much if I haven't tried something with the Ph. I was getting the TA to about 70 and then adding muratic acid to get the Ph in range, without success. When I was too busy to mess with this, the TA stayed around 70 with the Ph very high. This past weekend the TA was about 70 (maybe lower) when I added a bunch of acid and that drove the TA to near zero. I am using the TF test kit for the TA test and the standard Taylor drop test for the Ph test. The TF kit is old (~ 3 years). I was planning to buy a whole new kit in the spring. I just bought a new Taylor Ph vial (from Leslie's so who knows how fresh it is). I also agree that I don't see the connection between going from a cartridge to a sand filter would be part of this problem. I was routinely adding muratic acid because of the SWG, but before the sand filter the TA rarely moved off 90. So from all the advice it appears to me that I've not gotten the TA high enough before trying to bring the Ph down. I will get the TA higher before trying to lower the Ph and let you know the results. Thanks again for all the tips.
You shouldn't need to be adjusting the TA at all. If you're purposefully raising the TA, you're just fighting yourself. I suspect your reagent is bad and giving you a false reading. I think I'd get some TA reagent and see what it shows.
P.S. No guarantees but, Dave usually puts the TF-100 complete refill kit on sale in the spring so you may want to just get some TA reagent right now and wait to get the refill.
P.S. No guarantees but, Dave usually puts the TF-100 complete refill kit on sale in the spring so you may want to just get some TA reagent right now and wait to get the refill.