Calcium deposits

[guydot]

My pool was re-plastered last season. Throughout the season last year I fought with high PH levels and had to add A LOT of acid to bring it to range. When I opened the pool a few weeks ago, the walls were covered with white/crystal deposits, small white dots, which I am pretty sure are Calcium deposits. The calcium level last season was in range. The PH level when I opened the pool was very high.

I used 3 bottles of Leslie's Stain and Scale Remover (per the instructions and also kept the FC levels ) and it helped quite a bit but it is still there after about 10 days.

What should I do?

 

[Texas Splash]

What should I do?

Not knowing anything about your actual chemical history since the re-plaster, all you can do now is use the PoolMath tool to your advantage. Enter all of your test numbers and water temp into PoolMath and see what your CSI level is. If it's anything over 0 (nuetral), lower it between zero and negative 0.3. The 4 main players to your CSI are pH, water temp, CH, and TA. PH has the most immediate effect. If you have questions about any of this, you can post a full set of test results and let us compare.

 

[guydot]

I have been trying to keep PH levels low. The calcium crystals are slowly dissolving.
Pool guy added 2 qt of a product called Orenda SC-1000, which depleted the Chlorine, I have been adding CL every few hours.

FC: 0 - 0.5
PH: 7.2
TA: 40
CYA: 45
CH: 220
Water temp is 77

Since the crystals are slowly dissolving, I am not sure if I should adjust the TA?

 

[Texas Splash]

It may not be a bad idea to bring the TA up to at least 50-60 for now. 40 is a bit too low for comfort. Continue to manage that pH and I suspect you'll see more deposits slowly dissolve and/or break loose. Watch your FC as well. No need to use anymore of those Orenda products. The low CSI level will do the work for you.

 

[guydot]

I have seen dramatic improvement overnight. I must been doing something good... In may places the crystals are almost gone.

Not sure what to do in the future. The water here is soft. When I closed the pool, hardness was 220 and dropped to 160 over the winter. It is probably a good idea to close the pool with a much higher level of CH, say 350.

Also - PH levels continued to shoot up throughout last season and when I opened up. Before replastering I did not have this problem, so it must not be a result of the SWG.There is a section here that talks about over correction of LSI and PH shooting up after every time you add acid: What Causes a High pH in a Swimming Pool? However, I am not sure what the practical implication is (i.e. what I should do)

 

[Texas Splash]

Before replastering I did not have this problem,

Very typical of new plaster as it cures. The increased pH rise could continue for months. All you can do is monitor and adjust. It sounds like you're on the rigth track. Stick close to the PoolMath tool to monitor all your levels and CSI. Have a good weekend.

 

[guydot]

I continue to have issues with my pool. Here is the timeline:

Mid July - to remedy the calcium deposits, the installer did a "mild acid wash" or what I've seen hear called "zero alkalinity treatment" - he added a large amount of Muriatic Acid to the pool for 3-4 days and then brushed the walls. The pool looked GREAT after this. Right after the treatment, water was balanced with CH level at 320

Since then, the rising PH continued to be an issue and I needed to add acid on a daily basis. Probably a gallon a week. CH has been rising as well.

Now - end of August - I start to see calcium deposits forming again!!! CH level was 400 a couple of weeks ago and now 600!!! I added NO WATER to the pool. Only rain water. Current test:

FC: 1.5
PH: 7.6
TA: 70
CYA: 50
CH: 600!
Salt: 3300
Water temp 77

CSI = -0.03

I am totally lost here! So frustrating! I think that the CH is coming out of the plaster - where else would it come from? I have a gut feeling that the rising PH is a factor but I have no idea what to do. The pool was replastered last season... Could it be an issue with the materials used?

 

[duraleigh]

Sorry I didn't see your thread sooner.

It is probably a good idea to close the pool with a much higher level of CH, say 350.

No, that's not what you wanted to do. You wanted to bring CH to about 200-250 or so and then manage your pool to keep it there. For your CH to rise that quickly, you have been adding some on your own or chlorinating with Cal Hypo......right?

Please put your city and state in your sig.......it is important to the advice we give.

 

[guydot]

For your CH to rise that quickly, you have been adding some on your own or chlorinating with Cal Hypo......right?

That’s the thing - no. I have a salt pool, so chlorinated using the SWG. No tap water added. Just rain. Plaster installer is saying that the CH is still suspended in the water after his treatment but cannot explain why it’s been rising or the PH shooting up. He advised to add stain and scale and replace some of the water.

I have been adding acid almost every day just to bring the PH down. TA has been 70-80. I am in the Philly area. Added to my sig. thanks!

 

[duraleigh]

Your CH doesn't add up. PA generally has pretty soft water and your tests confirm that. Since your pool was replastered last year, it SHOULD NOT be throwing off calcium any longer.

Confirm this.....you started this season with a CH of 160 and now your CH is 600 without you adding any CH to the pool with Cal Hypo or any other chemistry......is that correct?

 

[guydot]

Confirm this.....you started this season with a CH of 160 and now your CH is 600 without you adding any CH to the pool with Cal Hypo or any other chemistry......is that correct?

Not exactly. Here is the timeline. My very water is soft but no water added this year other than refill to the tile when opened.

Timeline:
Summer 2018 - replaster. Fought with rising PH for the entire season. Closed pool with CH 220.
May 2019 - pool opened. CH = 160. Calcium deposits all over the walls. Small white dots sharp as heck.
May 2019 - July 2019 - I added CH to bring it up ~220 and then ~300. Leslie's stain and scale added + Orenda SC-1000. Made a difference but not enough. Still fighting with high PH, so added Acid a little more aggressively to reduce PH but never below PH 7.2. Kept Alkalinity 60-80.
Mid July 2019 - installer does acid treatment - adds 10 gallons of Acid, circulates for 3-4 days, brushes the walls, brings PH back up. Deposits fully removed. Measured CH right after = 320.
Mid July 2019 - Aug 2019 - only added Acid and Salt and Baking Soda to adjust Alkalinity to 70-80. CH was rising to 370 early Aug. Some signs of deposit.
End of Aug 2019 - I was away for a few days, did not add Acid. PH high, more deposits show. Measured CH = 600.

FC: 1.5
PH: 7.6
TA: 70
CYA: 50
CH: 600!
Salt: 3300
Water temp 77

CSI = -0.03

 

[duraleigh]

I get the timeline but that still doesn't make sense. How are you testing?

Calcium deposits are (simply put) when your pH goes too high and you don't reduce it. Obviously, you need to keep your pH down REGARDLESS of how much acid it takes.

The more CH you have in your water, the greater tendency for calcium deposits.

It's a little more complicated than that but keep those ideas in your mind. Do we know the CH of your fill water (I know you have used very little)

 

[guydot]

still doesn't make sense. How are you testing?

Agreed. I am going nuts over this. I use Taylor K-2006, as recommended here.

The more CH you have in your water, the greater tendency for calcium deposits

This article claims that low CH causes crystals. That's why I was hoping that CH of 300 would be helpful (Calcium Crystals vs. Scale).

The only other thing I added is Dry Acid to control PH. I don't think it raises CH?
I am on a business trip but will measure my tap water hardness on Friday. That being said, I did not add any water since the opening in May.

 

[mknauss]

Have you been using dry acid extensively?

 

[guydot]

About 10lb over the last month+

 

[mknauss]

Dry acid is sodium bisulfate. It leaves sulfates in the water. As they build up, they can corrode metals (SWCG) and cement (plaster).

You should not use dry acid in your pool.

Your scale issues may be calcium sulfate. I am not sure how that effects the CH test.

Let's ask @JoyfulNoise for his input.

 

[JoyfulNoise]

Calcium sulfate scale is not pH driven and can form at almost any pH if the individual calcium and sulfate levels are high enough. They will look needle-like in their structure. The spots could be sulfate crystals or carbonate. A newly plastered pool that is closed over winter and allowed to let its pH drift can easily go very high in pH and cause calcium carbonate scale. This is not an unusual event in cold winter climates with plaster pools. The only way to remove the scale is through maintaining a low saturation index water volume or by doing the zero alkalinity treatment. I would be careful with the zero alk treatment though - the pool should not go for more than a day or two with zero alkalinity or else you’ll start to seriously impact the plaster surface making it more rough and more susceptible to calcium scale and algae.

 

[guydot]

A newly plastered pool that is closed over winter and allowed to let its pH drift can easily go very high in pH and cause calcium carbonate scale. This is not an unusual event in cold winter climates with plaster pools.

How do I avoid the high PH in the winter? The pool has a cover. It would be difficult to add acid and circulate. New plaster looked nice but turned out to be a major pain!!!

 

[JoyfulNoise]

How do I avoid the high PH in the winter? The pool has a cover. It would be difficult to add acid and circulate. New plaster looked nice but turned out to be a major pain!!!

There is no easy solution here. All you can do is lower your CH, pH & TA prior to closing to achieve a negative CSI and then add a full dose of a sequestering agent like ScaleTec and hope for the best.

 

[guydot]

All you can do is lower your CH, pH & TA

How low should I go with the PH and TA?