PH Will Not Lower - Existing Plaster/Scale

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ontherocs

0
Mar 17, 2010
40
Tustin, CA (Orange County)
it's been a little since i've had to jump on. one thing to note... EACH time i've come to you guys, there's been an easier most cost effective solution. THANKS!!! searched the forum regarding this issue and found a few threads but each seem to deal with new plaster pools. this pool was replastered 5 years ago. bear with... going to data dump before getting to the root of this note in case any of the info will help with your answers.

been battling the high calcium in our area especially since we've gotten pretty near ZERO rainwater and are now dealing with drought restrictions because of it. last year it was calcium nodules: Calcium Nodules in Pools. couldn't get the epoxy to work so have just been manually scrapping the deposits off. unfortunately, there's discoloration that remains on the surface even with the manual scrapping, but knowing the cause helped us not go crazy with thinking it was because we were doing something wrong.

this year we started noticing actual scaling throughout the pool and most recently little white flakes settling on the pool floor.

first, replaced our SWG cell because it was at its end of life and not able to hold a high enough salt reading to stay on and generate chlorine even with cleaning it weekly and resetting the system after each cleaning. thanks again to the forum for being able to search for guidance on resetting the system. even with weekly cleaning, there was enough scale on it to be surprising based on the past cleaning history.

next, had a new valve added to the system which prevented back washing into the pool each time the pump turned off. this was originally done to battle the flakes on the pool floor thinking they were coming from the DE filter due to uncontrolled back washing. the valve installer stated the flakes were actually coming from the old SWG cell and its calcium self cleaning properties.

have been cleaning the pool with our dolphin which luckily collects ALOT of the flakes that then get dumped out instead of recirculated. because of the drought restrictions, have also been dumping our shower water into the pool which passes through our tankless water heater's descaler.

the new cell is AMAZING so much so that i have been performing basic readings on a regular basis to get an idea of how low a % the system should be set at. as of yesterday, it's at 40% which is unheard of for us during the summer months. the calcium flakes have also reduced drastically.

this weekend performed a more thorough water testing and found that the TA was at 100. decided to pull out my new "detachable fountain" to lower PH and TA and aerate just to get everything in perfect sync...

2.5 gallons of 14.5% muratic acid and 2 days later and i haven't been able to get the PH lower than 7.5. it was originally at 7.8. yesterday, each time i tested 2 hours after adding a portion of acid (2g total), the tests all came back 7.5.

here are the numbers as of this morning's water collection:

FC 5
PH 7.5
TA 90
salt 4000
CYA 70
borates 30
CH off the charts... i literally get tired of counting drops.


have the right steps been taken? is it harming anything if i keep on dumping acid in to try to get the PH down to 7.2 and begin aerating?

on my way to homie D to pick up more acid and have water collected just to see what leslie's #s end up being just in case my tests are way off.

on a related note... haven't searched yet, is there a need for us to go as far as doing an acid wash to clean up the scaling and nodules? is it easy enough to do one without having to drain the pool?

sorry for the novel. figure it might help somebody else tho with all the facts.
 
The borates won't do that much in preventing the lowering of the pH, especially as far as it should have dropped. I calculate that 2.5 gallons of 15% hydrochloric acid in 29,000 gallons with the numbers given (including the borates) should drop the pH from 7.5 to 6.9. Of course, as the pH gets lower there will be more carbon dioxide outgassing so one might end up only at 7.0 or 7.1 or so depending on how long one waits to test. So something is very wrong here. Either the acid is not acid or not very strong or the pH test is wrong.

Does the acid smell like Muriatic Acid where it is quite irritating? The half-strength won't fume as much but if you move your had over the top of the container to carefully waft some towards you it should still be quite noticeable (do NOT put your nose directly over the bottle). Or you can add some to some calcium carbonate or put a drop in an innocuous part of your concrete, see it bubble/foam, and then rinse it off.
 
Ok, I'm not up on my chemistry as well as some of the others here, but didn't you say that you pulled out a fountain did you mean you put it in the pool? Do you have it running now, or did you remove it from the pool? If you are aerating with the fountain then this will drive up your PH.
 
thanks for responding Agent99, chem geek, dieseltim2!!!

didn't get out of work early enough to have leslie's test anything yesterday so just picked up acid. ran short of time this morn to either test or gather new testing water for leslie's so...

got home tonight and pulled out my TF100 and speedStir (new>LOVE that thing!!!) and decided to do the more accurate FC and TA test instead of the basic or blue devil drop test. Amazon.com : Taylor 9265 - Magneticstirrer, Speedstir, Start-Uppack(Uses9198 Garden

FC 6.5
TA 70

used the TF-100s basic for the PH cuz that's all i have now and it came up slightly higher (darker) than 7.5. is there a more accurate PH test other than the basic one? looked on TF's site but didn't see one that could be purch'd separately.

was a little concerned cuz my basic chems are older; but, seeing that the FC isn't way off between the two different tests, thinking it's good. the TF-100 chems were just recently replaced.

chem geek the PH originally started at 7.8 before the acid dumping. only .5g was added at 1st, waited 2hrs with pump running and retested at 7.5, added 2/3g etc..., that's when i started noticing the PH was sticking at 7.5

when searching prior to starting this thread, i KNOW i read somewhere that cloudy water or scale could cause acid to not lower PH as normally expected. man, if i can't find that comment ANYWHERE now. >.< that's the only reason why i continued adding acid.

don't have any more of the acid, but it's the standard homieD stuff: Kem-Tek 1 Gal. Swimming Pool Muriatic Acid (2-Pack)-335 - The Home Depot. however, i can say that when pouring it into the water, i did notice the solution swirling as it was mixing. you know how syrup looks when being dissolved in water.

dieseltim2 i only pulled the "fountain" out of the box and tested adding it to the jet before starting the original process. it didn't stay in to aerate cuz the PH wouldn't get to the 7.2 suggested in poolSchool. i did read somewhere else in the forum that having an SWG does some aeration? is that enough to not need to also and the fountain when trying to balance chems? Amazon.com : Splash-A-Round Pools SEC385 Waterfall Spray Pool Fountain : Swimming Pool Pump Accessories : Patio, Lawn Garden

not sure where to go from here now that the TA is ideal. drop the mystery??? boooooo... would really like to know what the heck was happening.

any thoughts on my related note... haven't searched yet, is there a need for us to go as far as doing an acid wash to clean up the scaling and nodules? is it easy enough to do one without having to drain the pool?
 
You are right that if one is dissolving scale then that would raise the pH counteracting the acid that is added. If that were happening enough, then you should see both the CH and the TA rise while the pH is constant assuming you are adding acid to maintain it. What you noticed, however, was TA dropping while the pH was stuck. That happens when there is carbon dioxide outgassing or if calcium hydroxide is converting to calcium carbonate in plaster (as with a bicarb startup).

Yes, now that the TA is where you want it don't worry about how it got there. Though we like to know what is going on, there are times when we need to let go and move on and hopefully see another situation where the processes are more clear.

As for scaling, what some do is maintain a negative CSI and if the scale isn't too old it will tend to redissolve into the water. If that happens, then you could see what I described above in terms of rising CH and TA. To keep the TA from rising as much, aeration will help during the process, but at least you'll start to get rid of the scale. As for calcium nodules, you may need to remove the nodules perhaps with a pumice stone if they don't dissolve along with the scale.
 
good morning!!!

thanks chem geek! your explanations helped a lot!!! oh the things one learns on this site, sometimes after the fact... >.< A Bicarb Start-up guide for TFP members

our pool setup was so botched. live and learn! New Onyx Quartz Pool Care Suggestions Please

compared tests this morn and both the TF-100 and basic are in line. the blue devil kit reflected hi'er results is old and not the site's recommended kit so it's now in the trash. ;)

FC 5
PH 7.8
TA 80

as directed by poolMath, dumped ~3/4 of a gallon of acid in about 1/2 hr ago. will test in 1.5 hrs and see what comes back.

chem geek i meant to do the acid smell test prior to pouring the new bottle in but forgot until after the pour. doh! so attempted the wave over the opening with the remaining 1/4 and got nothing. figured, wth and just sniffed the opening directly. eh... maybe a bit of acridity but not like i know it can be. i'll try to remember with the next bottle. seems like the 14.5% is the LOWEST level of acid out there tho, so no wonder?

forgot to bold this question above so asking once more:

used the TF-100s basic for the PH cuz that's all i have now and it came up slightly higher (darker) than 7.5. is there a more accurate PH test other than the basic one? looked on TF's site but didn't see one that could be purch'd separately.

thanks again TFP for all your help!!! has made pool owning easier and a great learning!
 
For pool chemistry the Taylor kit works well for most users. It helps to read the block in front of something that is white and a few inches away from it. You can play with the distance that makes the color more distinct.

If you want something to measure the pH a little more accurately you could use an electronic pH meter. However, those need to be calibrated every so often to make sure they are accurate.
 
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