Scale, I need help please

[Lykly]

I have what I think is a scale problem. First let me give you a little recent history. The other day I noticed white specs along the floor of my pool pretty much throughout, at first I thought it might be sand since we did have some wind, and I vacuumed it up. After I started vacuuming it up I realized it appeared to be a white type of soft scale. I thought maybe I let my pH drift too high, but in reality I don't think I ever a let it approach 8, really I don't think it ever got past 7.8. Anyway I was careful to keep my pH in order and after I cleaned it up I thought the problem would be done. Today coming home from work I seen in the wading pool what appeared to be an excessive amount of the same scale. I seen it in the shallow wading pool and also on the steps coming into the wading pool. Also on the sitting benches on the deep end of the pool, which would probably be about 16 inches deep I see some scale there as well. As of right now I do not see any in the deep end or even in water that is three or 4 feet deep. I will attach some pictures, here are my latest test results I just took with my TF100 kit.
Ph in deep end (6') - 7.3
Ph in wading pool - 7.3
CL- 6
CC - .5
CH - 325
TA - 130
CYA - 65
Salt using K1766 Kit - 3200
Temp - 86

Only things I have added to the pool other than the salt when I installed AquaRite AQRT15, is 20 Baum Muratic acid and 8.25% Clorox. I have been meticulous about my water chemistry and the water is actually very very clear.

I have reduced the TA almost in half, but it has been hanging around 130 for quite some time. I think this is due to the fact of evaporation and I have to add water now and then. I use well water, which as a TA of around 300, and also calcium hardness of around 350. All my tests showed zero iron or metals. Metal tests from Pool store and Culligan.

I took some of the scale and captured in a glass, and added vinegar, it did not attack it right away but after a while it did disappear. When I try to grab the scale it pretty much just dissolves. I did taste it, and it did not taste at all like salt. Of course I was careful not to ingest any. Hopefully I provided you enough information to hopefully help me solve this problem. Do you think it has to do with the SWG? We did have the pool replastered, but that was back a few months ago. Open till this point, I have had perfect water.

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[Lykly]

I thought I would add a couple other pictures, the one with the pool cleaner is in about 3 feet of water the one with the diving ring by drains are in 6 feet of water. (The white you see is not scale it is a diamond ring handle)You can see the water is clear and no scale on the bottom of the pool. The other picture is the bench in the deep end and you can see some scale precipitating out. It appears to be only in shallow water, which I am sure is much warmer than the rest of the pool. Temperatures of been near 100 here for the past week or so.


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[Lykly]

OK just vacuumed it up, I was wrong, there is small amounts of scale throughout the pool, just not very much, majority of it precipitated out in shallower water. Wondering if I should lower pH further?


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[pooldv]

Yes, that is scale forming in the SWG and the pool surface is not far behind. The good news is that it is relatively easy to manage and managing it will make your SWG last a couple of years longer and your plaster will last many years longer, maybe a decade longer.

Enter all your test results into Poolmath and it will give you a CSI number. Lots of things affect the number, salt, ph, ta, ch, temp, borates. But, it is usually easiest to tweak PH and TA to change the number. Keep your CSI number between -0.3 and 0 to prevent scale.

More here, Pool School - Calcium Scaling

 

[Lykly]

-.28 is the number I get with my pH of 7.2, which is where I have it now.....Once my TA comes down I can let my pH drift up a bit it looks like by playing with the numbers. I had been keeping it around 7.6 which gives me a number of .1 which apparently is enough to cause the scale? I did remove my SWG cell today and it looked very clean.


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[pooldv]

You know where all the scale in the SWG went. 0.1 should not cause scale.

 

[Lykly]

The link says to keep the index below .6, I have never even come close to that, is there anything else I could've done to cause scale? The CH in my water at 325, is that sufficient? I'm hoping I'm not pulling any calcium out of my new plaster. Also, is it normal for my SWG to be perfectly clear of scale? I just want to be sure I get a handle on this before I have big problems.


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[Lykly]

You know where all the scale in the SWG went. 0.1 should not cause scale.

What concerns me, my index never got much above.1 if at all. What else could be causing this? I appreciate your help.


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[pooldv]

My SWG has stayed clear and never needed cleaning and it is starting season 5. There were most likely times when the CSI was high. Keeping CSI slightly negative will definitely prevent scale and is good for your SWG and plaster in all cases.

 

[Lykly]

What is a good target for my TA? I see people have it all over the place with success. Mine seems to be hanging at 130, maybe be keeping my ph at 7.2 rather than 7.5 it will one down? Once it comes down I can have my ph at 7.5 and keep the index slightly negative. I know my TA should be lower than it is.


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[pooldv]

Any TA number is fine if your PH doesn't rise too quickly and your CSI is OK. TA will lower on its own through acid additions to lower PH until PH and TA reach equilibrium. It is different for all pools and regions. For our area TA between 60 and 80 and PH 7.6 to 7.8 seems typical. There is no need to actively lower TA unless your PH is quickly rising and you want to lower it to reduce PH rise or to reach a CSI number to keep the pool in balance.

The goal is to let TA and PH find equilibrium and no longer have to regularly add acid acid to maintain PH.

 

[Lykly]

My TA is at 130, and I have to add acid daily, but it does not seem to be lowering. But I've just been maintaining pH of around 7.5 - 7.6. Looks like I'll have to start maintaining it at 7.2, hopefully this will lower the TA, once that's lowered to about 100 it looks like I could maintain PH of around 7.5. I'm guessing since maintaining around 7.5 and the TA remaining the same is an indicator I need to be more aggressive on the pH to lower the TA? At any rate, no scale in the pool this morning so far, I will keep the pH lower. I am still a bit confused as I tested almost daily and the CSI rarely got positive maybe up to a .2 on occasion. Water chemistry doesn't lie, so apparently I must've let that index get high for a short period of time without knowing it. Live and learn. Appreciate you taking the time to discuss this with me, last question for now would be how low can I bring ph to lower alkalinity without being dangerous? Thx pooldv.


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[Mr Bruce]

You constantly rising pH is more to do with your new plaster than TA. You're going to have that fight all summer, I am sorry to say.

 

[Lykly]

You constantly rising pH is more to do with your new plaster than TA. You're going to have that fight all summer, I am sorry to say.

Thank you for reminding me of that, I still believe my TA is a bit high? Would you agree with that? Trying to figure out what would be a good target.


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[pooldv]

Good point Mr Bruce. It takes about a year for plaster to fully cure and stop contributing to PH rise. The high TA is also contributing. Also, any waterfalls, bubblers, etc will cause PH to rise. 7.2 is as low as you want to go. To actively lower your TA follow this process, Pool School - Lower Total Alkalinity

 

[Lykly]

10–4, thanks guys, I will let you know if I see more scale, following this advice I should be done with the dirty rat! Haha


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[Lykly]

Well I am at a loss, I come home from work today and I can see scale starting to appear again. My CSI is -.2.
My numbers look good, here they are:
CL-5
Cc-.5 if that
TA - 125
CH - 325
Ph -7.3
CYA - 65
Salt- 3100
Temp 86
CSI = -.2

I don't understand what can be causing this? I thought scale could not form with the CSI with a negative number?
Could this be scale that was still in the system, or should the water in its condition dissolve it? I don't want to let this get out of hand.




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[Lykly]

Can the RPM of my pump while the SWG is operating cause problems? I have it running around 2100 RPM so it can also feed water to my Polaris discharge cleaner. Maybe slowing the pump down will help? Not sure if that makes a difference or not.


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[pooldv]

No, it is not the pump speed. Scale formation and getting rid of it is not a day or week thing. It is weeks to months, even years, long to develop and will take at least days or weeks to end. Scale develops only because PH, TA and CH allow it. Scale doesn't develop if you manage the numbers to prevent it. What changing your CSI to slightly negative does is prevent scale from developing in the future. All existing scale is still there and will take time to brush away and dissolve.

 

[Lykly]

Well, that is a relief to hear. Should I clean my filter? I put in new filter elements when I had to re-plastered a few months ago, the pressure is staying where it always has around 10 pounds, do you think I should clean it? If I would have been thinking I would have vacuum to waste, I had that option. If I end up vacuuming again I will definitely vacuum to waste. I can't believe I didn't the first time, but that was my first time ever vacuuming, live and learn I guess.


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