Still Scaling with Negative CSI

[MWigs]

First time posting, so here goes. I did do some research and found a lot of great info (Thanks!), but not an answer to my specific questions/issues.

My pool has had high acid demand (up to 2 gallons per week) and scaling issues since it was new. Adding that much acid would crush my alkalinity, so it was a constant battle between low alkalinity and high pH. Originally I followed the Taylor kit recommendations for chemical levels, then was introduced to TFP in October. I have been using the TFP guidelines since roughly November, and my acid demand has gone down dramatically (but then so has my water temp). My pool builder gave me a sample dosage of a Natural Chemistry product called Foundation, which boosted my borates to 15 ppm. I would like to increase it to the TFP recommended 30-50ppm, but just haven't gotten around to it.

Here are my test results from Saturday 2-7-2015 (Taylor K-2005 + TFP FAS/DPD):

FC: 3.5
TC: 3.5
pH: 7.6
Alk: 60
CH: 310
Cyn: 90
Phos: 0
Borates: 15
Water Temp: 62F
Salt: 2900

When I plug these numbers into Pool Math, I get a CSI = -0.7. I have checked all of my chemical tests going back to December, and I am always on the negative side of the CSI scale, and yet I still see scale developing. Now I do have a black bottom pool, so it is definitely more visible. I just don't know why this keeps happening when I am close to being corrosive on the CSI scale.

I have drained and acid washed the pool once. My spa has been done twice, and I am told it can't be done again. My builder is suggesting we try the Jack's Magic before draining again.

What am I missing? Thanks in advance!

 

[Patrick_B]

Welcome to TFP.

If your numbers have looked like that since you started and you're having scale issues, I'm at a loss. They do not point to scaling tendency just looking at this snapshot. Is this similar to where you have been, and are you certain it's been scaling?

 

[JasonLion]

Welcome to TFP!

There are really only a few possibilities. You are experiencing something other than scaling, your test results are way off, or the water chemistry is varying dramatically and isn't always at the numbers you listed.

 

[MWigs]

When I started the pool in June 2013, I balanced the water using the Taylor book in my kit. The big difference with the TFP recommendations was Taylor uses lower stabilizer: 30-50. At that lower cyn level, and water temps in the 86-92 degree range, I was seeing an increase in pH levels of 0.2 per day. I would knock it down to 7.4, then it was 7.6 the next day, and so on. That is why I was using so much acid and crushing the alkalinity.

Since I have increased my stabilizer/cyn levels and am using the TFP suggested levels, my numbers have been in this range:

Water Temp: 60-82 degrees
FC: 2-6
Alk: 60-80
CH: 300-400
pH: 7.4-7.8
CYN: 80-100

One thought I had was that maybe the scale formed late summer when I wasn't using the TFP method, and is only showing up now with the colder water??? I'm not sure that makes sense, but I am definitely seeing more scale. Like I said, with a black bottom pool, it is easy for me to see. I am pretty certain that it is scale. When some light patches formed on my sun shelf recently, I poured acid on them through the 3-4" deep water and it bubbled off. I just wish it was that easy with the rest of the pool.

I was testing my water daily, and based on the pH rise, adding about a 1/8 gallon per day. When the water temps dropped, and I started using the TFP chemical levels (and after adding that Foundation product), I could go a few days between testing because the pH didn't rise as much. One thing I also notice, and is interesting to me, is that my pH doesn't want to stay in the low range (say 7.4) but doesn't go much above 7.8 if I ignore it for a week. In other words, it seems to jump pretty quickly from 7.4 to 7.6, then settle at 7.8. Probably because that is the output pH of the Aquapure SWG.

Here is a sample of test results from January: Acid = Muriatic Acid, PP = Pool Perfect + Phos free, Boost = Run SWG@100% for 12 hrs, Salt = 2700-3000 for all tests

1/17/2015 1/18/2015 1/20/2015 1/24/2015 1/27/2015 1/31/2015 2/3/2015 2/7/2015 2/8/2015
---------------- --------------- ------------- ------------ ------------ ------------ ----------- ----------- -----------
WT: 66 deg WT: 64 WT: 64 WT: 71 WT: 68 WT: 64 WT: 62 WT: 62 WT: 64
FC: 1.5 FC: 2.5 FC: 2 FC: 2.5 FC: 2.5 FC: 3.5 FC: 3.5 FC: 3.5 FC: 3.5
pH: 7.8 pH: 7.7 pH: 7.6 pH: 7.8 pH: 7.7 pH: 7.6 pH: 7.8 pH: 7.6 pH: 7.7
Alk: 70 Alk: 70 Alk: 70 Alk: 70 Alk: 70 Alk: 70 Alk: 70 Alk: 60 Alk: 60
CH: 330 CH: 340 CH: 350 CH: 310
CYN: 90 CYN: 90 Add 1/8gal acid CYN: 90 CYN: 90
Boost CL Set SWG = 25% Phos: 0
Add 1/8gal Acid Add 1/8gal acid Add 1/8g Acid Add 1/8g acid Borate: 15 Add 1/8g acid
Add 3 caps PP Add 3 caps PP Add 3 caps PP Add 3 caps PP

 

[JasonLion]

You are using a good test kit, and your logic is sound, but the results are not consistent with what is chemically possible.

Cold water will tend to have a lower CSI value than warmer water, assuming nothing else changes, making scaling even less likely.

Your PH is going up because of aeration provided by the SWG. The rate at which the PH goes up is higher when the PH is lower, and at higher PH levels can get so slow that the PH effectively stops going up. The PH is going up less now because raising your CYA level reduced the amount of time the SWG is running, which means less aeration.

Can you describe the scaling in more detail? What color is it? Is is smooth or rough compared to the rest of the pool surface?

 

[H-12 1/2 Mike]

My ph was rising like yours until I detected a leak and shut down my pump. I continued to test my water daily and noticed my ph was no longer rising. After repairing e the leak I determined the rise in ph was caused by the aeration caused by the spa overflow and waterfall. I programmed my jandy valves so that the spa overflow would only overflow 1 hr per day. Result: Instead of adding acid daily I only add 8 oz of acid once a week.

 

[JamesW]

Do you have any type of dust that gets in the pool on a continuous basis? Some types of dust can stick like scale. Dust from cut concrete, fine sand etc.

Your water temperature has been as high as 92 and the calcium has been as high as 400. With those numbers, it wouldn't take much of a pH rise to get you into scaling range. With new plaster, it can be easy for the pH to get too high.

I would recommend that you discontinue the phosfree.

Do you brush the pool on a regular basis?
Have you used dry acid or sequestrants? If yes, how much and how often?
Do you ever use sodium carbonate?
Have you ever added calcium chloride and bicarb on the same day?
Are you getting scale in your salt cell.
What is your filter pressure at various RPMs?

 

[Lux Man]

Does the scale appear anywhere other than the bottom surfaces? Is there any on vertical surfaces? BTW using Jack's Copper and scale can be a challenge because you need to be able to by-pass your heater. You need to drop the PH way down while it does it's thing and it's not cheap either. (takes several days) Not many pools are plumbed with a heater by-pass around here. We'd either re-plumb or use a portable pool-side filter. I've actually only used it once- the pool had CH over 800 and TDS of over 2000, no mystery it scaled.

BTW- you said your pool is black- what is the surface? Has it always been black? When did the scaling first become noticeable?

 

[Lux Man]

I'll explain where my last line of thinking was regarding my questions. Based on your previous remarks and those of others, could this be actually be leaching through rather than being from the water itself?

 

[Patrick_B]

I agree it's something else. These numbers just don't support scaling.

 

[pragmatic]

I'm fairly new as well and learning some of the terminology check out this thread: http://www.troublefreepool.com/threads/87968-White-scaling-on-my-new-waterfall-amp-disagreement-amount-chemical-levels Maybe the same type carbonate build-up from the mortar/cement.

 

[MWigs]

Thanks everyone. Sorry for the delay in response. We had internet issues at the house for a few days.

The pool finish is Pebble Tec Black Pearl. This is one color scale away from their darkest color (Jet Black, I believe). The scale looks like patches of grey dust on the pool surface. It is not rough. In fact, the scale seems to be only on the plaster media between the pebbles. Areas where the pebble is less exposed, and you see more of the plaster media, seem to attract more scale. The scale is all over: pool floor, walls, spa benches, and even the opening of the skimmers. I am pretty sure it is scale because I was able to remove it with my own acid wash in the shallow sunshelf. It bubbled up and dissolved away. It also currently looks just like it did the first time the pool scaled and was drained and acid washed professionally. The scale is even in some areas where it just looks like the pool finish is dull and not the vibrant black color it was when new; in other areas it is patchy and looks like grey dirt/dust.

In answer to JamesW, I do not brush the pool frequently. Once in a while. I do have a lot of bench seats and a sun shelf which I try to brush off each week to help the pool cleaner. I have not used dry acid or sequestrants, etc. I have tried "No Fume" sulfuric acid instead of Muriatic in an attempt to not reduce alkalinity as much, but that didn't seem to make much. The pool builder started the pool with Scale Free, and I continued the maintenance dosage until this year as it obviously wasn't working.

I switched from DE to Pearlite and had issues with the pressure rising and frequent backwashes. After consulting with a local pool store, I was told to use half as much (3 scoops). That seems to be working. although I have a variable speed pump, it runs at the upper rpm range to keep my spa runnels pouring correctly and not just running down the spa wall.

 

[Patrick_B]

More and more that just sounds like your plaster components/color and not scale. If you were scaling, I think you'd be leaving some on the pebbles too, not just on the base material in between them. Repeating what has been said...if your numbers have been like that in the past. Based on that, scaling would be very unlikely. Any chance you can post some pictures on the next bright day?

Your DE was doing it's job, and may have been picking up plaster dust from the new pool finish, acid wash/cleaning. You may or may not have enough media in the filter now, but you'll find out at some point before summer gets too far along. If you aren't cleaning the pool well enough with the filter, it will become evident. No big deal, you can always add more media or go back to DE and experiment to get the right amount if indeed you had too much in there.

 

[Lux Man]

Do you think the guidelines found here, http://www.troublefreepool.com/content/154-start-up-new-pool-plaster were followed when your pool was new during start-up? I don't think you mentioned the size of your pool or the turnover rate, but you may resolve the issue with brushing every day for a week, possibly more and running your pump/filter to catch the sediment.

 

[MWigs]

My pool builder did take care of the pool during break in, but I'm pretty sure that we did not follow the procedure outlined here (TFP). We were swimming pretty quickly after it was filled. I do know they waited a couple of weeks to add the salt.

The pool was acid washed in spring (March 2014) and the sunshelf was refinished (I wasn't happy with a seam). I wouldn't think that plaster dust would still be an issue 18 months later. My water quality is great, other than the scaling, so I am pretty sure that my filter is doing its job. The pump runs 8 hrs (winter) and 12 hours (summer) at about 3300 RPM. Like I said earlier, the pump has to run that fast to keep the spa runnels pouring properly. Does that sound like enough flow for a 22.5K gallon pool?

I tried uploading pictures, but it wouldn't work. Maybe the files are too large. There is what I believe to be scale on the lip of one of my skimmers. I poured muriatic acid on it and you can see the smoke-like look of the scale coming off. This procedure won't work where the water is deeper than a few inches. Would anything other than scale do this?

 

[Lux Man]

MWigs- I realize you stated what your chem readings were back in post #1 but if you don't mind could you test them again and tell us how you are testing them. It sure sounds like scale but how and why is a mystery.

 

[Divin Dave]

Hi Mwigs,
the best way to post pics is to put them in photobucket account. Then click on the pic you want to post and click the IMG button beside the pic. It will then be on your clipboard. Then paste the IMG code into your post. And viola, pics will appear.

 

[Patrick_B]

Good suggestion from Dave on posting the pics. What you describe reacting with acid sounds like scale, but yes other things will react with acid. Things like plaster, grout, cement. As when started, I am at a loss in telling you why you have scale based on the numbers you gave. It just doesn't add up with those parameters. I suspect at some point for some extended time you had numbers far outside those you have record of.

As for your pump run time (un related to anything scaling) you can likely cut down that run time a great deal. Sorry I'm not more help on the scale issue, but I can't offer more.

 

[MWigs]

Seems like a lot of hoops to post a few pics, but here goes:



Test results from today, Saturday 2-15-2015@11:15am:

Air Temp: 66
Pool Temp: 56
Salt: 2400 ppm (need to add two bags)
SWG: 20%
Filter: 20 psi

FC 4.5 (from TFP kit)
CC 0
pH 7.8; reduced to 7.6 w/ 1 drop of #5 Acid Demand reagent, and 7.4 w/ 2 drops of #5 Acid Demand reagent
Alk 60
CYN 80
CH 330

As for how I am testing, I follow the directions in the Taylor K-2005 kit. I tried to give a month's worth of test results a few posts ago, but the format didn't come out the same as it was typed.

- - - Updated - - -

OK, I think I have the picture thing down now. Here is my skimmer with scale.



- - - Updated - - -

Here is the scale melting away after I poured some muriatic acid on it:



- - - Updated - - -

Here is the skimmer after the "acid wash":



- - - Updated - - -

And finally, here is a close up of what I think is scale on one of my steps:



- - - Updated - - -

If you look closely at my "after" picture of the pool skimmer, you will see scale on the wall of the pool by the drain/pump inlet.

 

[Lux Man]

As stated above in post 11, I believe efflorescence may be the most likely cause. I have been doing my own research and talking with our trusted restoration company. He agrees that this is a strong possibility. If it were me I would contact the pool builder and ask him to come out and look at it for himself. If it is efflorescence, the root cause and remedy, could be difficult to nail down but he may be able to offer some counsel. He suggested the National Plasters Council site NPC would be a place to start. They will field questions from the public so I would give them a try too.