White scale in fiberglass pool

PoolGuyNJ

TFP Expert
May 20, 2007
3,192
South Central NJ
Re: White scale in fibreglass pool

First, understand that this is not a defect in the pool. This was a defect in the way the pool was maintained. That falls under your responsibility, even if you hired someone to do it for you.

Second, the removal process will take some time and may impact the gel coat's original shine. There won't be any way around it. The calcium build up you have cannot be "buffed out" without losing the gel coat, or at least a substantial portion there of. In all likelihood, the factory shine is going to be a memory. That's not to say it won't shine but I think you get my drift.

To remove the calcium, you will need to give the pool a long acid bath. There are a number of differences from the procedures the manufacturer suggested from what I would do.

I would cover any and all metal. I hope you have a sump or drywell to remove water from under the pool. You may need to empty the pool to cover the screws with silicone. Don't forget the screws holding the drain covers.

If there is no sump or dry well, be absolutely certain that the water table won't rise up to the level of the pool's bottom or it could float like a boat. If you can't be certain, then you will need a few well points driven down, connected to a pump, and any water drawn out and discharged either into a storm sewer or 50 meters away and down hill from the pool.

If there is a light fixture, it will need to be brought to the surface and set on the deck. The cord will survive the bath just fine. If the niche is metal, it will need to be coated with silicone also. You're going to be dropping the pH down to about 4 and that would eat any metals, as well as the calcium. The screws behind the skimmer face plate that hold the skimmer to the wall should be safe as there is a gasket between the wall and the faceplate. I see no need to disturb those connections as long as the screws are protected.

You will need a small cheap pump with a long cord such as on might use to drain a solid pool cover. It will be cable tied to a pool pole with enough cord to let the pump dangle about 1/2 to 2/3 the depth of the pool, 1/2 way between the deepest point and the start of the slope from the shallow end. This will provide the circulation in the pool. Your pool equipment will be turned off during the bath. The pump, when turned on, will spin around and around, slowly moving the water.

You will need rubber gloves.

You will need a test capable of testing water with a pH of 4 or else you will be taking an educated guess based on where your pool's pH and alk level are now and adding the acid.

Once everything is in place, and the pool is full, add another couple centimeters to get the water level above the calcium line. Add the Muriatic acid, 500 ml per ten minute period, at a time, slowly pouring around the perimeter, avoiding the steps and sun shelf as these are low circulation spots and you don't want the acid to sit there waiting to be disbursed. Add enough acid to drop the pH to between 4 and 5.

Brush 2x a day. Rinse the pool brush and pole immediately after! Wear the rubber gloves. Test the pH daily. Keep the little pump on constantly.

You should see results within a couple days. You will know it's working when you see the dust coming off the walls. You will likely see, as you progress, more and more dust on floor.

After about 4 days, most, if not all the deposited calcium should be off the surface and either on the floor or in solution. Neutralize the acid with dense ash (pH Increaser) and dump a foot of water to inspect your results. I would suggest vacuuming to waste to get the dust out. Make sure the wasted water is sent well away and down hill from the pool. If the results are not to your needs, refill and drop the pH again for another few days of treatment.

When you get to where you are satisfied, neutralize the water to a pH of 7 and dump it all followed by removing the silicone blobs on the screws, cleaning off the light niche, resetting the light fixture, and a fresh refill.

Get a proper test kit so you don't have this happen again.

Scott
 

fleetz54

Member
Jul 1, 2010
13
Castro Valley CA
Re: White scale in fibreglass pool

Hi Scott,

Thanks for that.

I suppose it would have nice to have known about this from the get go and it could have been avoided. The pool manufacturer has been great in assisting me as they had not experienced the issue until mine happened about over a year ago. They must have had another few and further investigation with industrial chemist's provided the solution (and prevention) and hence the Tech Bulletin which was released about one week ago.

The pool manufacturer in consultation with their industrial chemist provided me (free of charge) Organophosphonate which also states on the container it is Acid 8 very corrosive. At the chemists instructions I applied 12 litres based on the 50,000L pool capacity for two weeks checking every few days to see if the scale would turn milky or return to solution. After three weeks it was evident that the scale was not going to alter. I did not test the pH level.

Thanks for your input.

Regards,

Paul
 

fleetz54

Member
Jul 1, 2010
13
Castro Valley CA
Re: White scale in fibreglass pool

bjennifer said:
posting some pictures, these show the pool drained a foot or so and a few areas buffed out, however you can see how terrible the white surface is.

Interested in finding out which way you went to get your scale resolved?

What did the buffing look like after they did the few test patches? Did they use any special cutting compounds?

Thanks and regards,

Fleetz
 

kalyn2887

New member
Jul 29, 2012
2
Re: White scale in fibreglass pool

We have a fiberglass pool with the exact same white scale buildup. What did you use to buff the white scale off with?

Thanks!!
 

nomad26

LifeTime Supporter
Sep 2, 2012
55
Re: White scale in fibreglass pool

I also have a fiberglass pool with the same scale build up as long as its wet it looks ok but if you drop the water line or drain half the pool its all white scale . The pool was originally blue color from Viking.
Has anyone tried the acid bath that Scott explains in the post above ?
Any other ideas on how to remove this scale ?
Mark
 

PoolGuyNJ

TFP Expert
May 20, 2007
3,192
South Central NJ
Re: White scale in fibreglass pool

When a F/G shell is limed up (calcium scale) like the one in the picture, it didn't get that way quickly and nor will the cure. It formed because calcium got in the pool and CSI was positive for a lengthy period of time.

If you have a heater, its best to take it out of the water loop.

Drop the pH to about a 5 or so and run it (no swimming!). This will slowly dissolve the calcium that coated the shell over a period of days. Normal pump run times are used.

Expect the CH level to rise.

Check the hardness of the fill water.

Dilute the pool as needed. Never exceed more than 50% at a time. If you have a high water table, don't exceed dropping more than 25% unless you have a dry well/sump and can pull any water out from behind the shell.

Try to get the CH level under 300 ppm. Target the CSI to be slightly negative and scale can't form. Recoonect the heater once the pool is rebalanced.

Scott
 

nomad26

LifeTime Supporter
Sep 2, 2012
55
Re: White scale in fibreglass pool

PoolGuyNJ said:
When a F/G shell is limed up (calcium scale) like the one in the picture, it didn't get that way quickly and nor will the cure. It formed because calcium got in the pool and CSI was positive for a lengthy period of time.

If you have a heater, its best to take it out of the water loop.

Drop the pH to about a 5 or so and run it (no swimming!). This will slowly dissolve the calcium that coated the shell over a period of days. Normal pump run times are used.

Expect the CH level to rise.

Check the hardness of the fill water.

Dilute the pool as needed. Never exceed more than 50% at a time. If you have a high water table, don't exceed dropping more than 25% unless you have a dry well/sump and can pull any water out from behind the shell.



Try to get the CH level under 300 ppm. Target the CSI to be slightly negative and scale can't form. Recoonect the heater once the pool is rebalanced.

Scott
Ok this I can try with my limited skills.
I can bypass my heater.
Drop the PH to 5%.
Run the pump on normal times.
I should expect the Calcium hardness to rise.
And here is where you start to lose me.

Check the hardness of the fill water ? That one confuses me . Am I filling the pool with fresh water ?
I am confused with diluting the pool as needed never exceed more then 50 percent at a time ?

I do not have a dry well / sump, I would guess my water levels are low in my area. I live in California in a warm valley, for 5 to 6 months we do not have any rain, when we dug the hole for the pool the soil was very hard clay.
I understand getting the Calcium Hardness level under 300 ppm,
The CSI I need to read up on not sure what that is.
My understanding is I am dropping the ph down to 5 and by pass the heater and circulate the water the other parts after that I am not clear on what exactly you want me to do.
This sounds like it's going to work and I want to try it.
I just want to have a better understanding of your instructions.
Also keep in mind I am new to this and a bit slow.
I do appreciate your help
Looking forward to hearing back from you.
Mark
 

LauraJ

Gold Supporter
May 23, 2012
16
Tuscaloosa, AL
Re: White scale in fibreglass pool

Nomad26, I'll be interested in hearing about your results. I have a fiberglass pool with the exact same problem. I'm quite confident the maintenance is what caused the problem. Since I'd tried everything to get get the scale off, I'd kind of decided instead of a deposit, I'd somehow managed to bleach or etch the surface. Once swimming season is over for good, I might try Scott's process. However, I'm afraid of the damage I could do to everything other than the scale.
 

nomad26

LifeTime Supporter
Sep 2, 2012
55
Re: White scale in fibreglass pool

LauraJ I will let you know what happens with the process. I was thinking of trying it on my hot tub spill over that has the same scale build up on it,
Before I try it on the larger pool .
I am also a bit afraid of the damage it might cause to the plastic jets and the fiber optic light that cannot be removed from the pool or the hot tub.
I really want to understand the process better before I try it . I am a bit confused still on exactly what the steps are.
Keep me posted as well
RIght now I need to drain all the water out of the pool to remove my high CYA levels.
I can live with the scale for now . I just thought I would try to kill two birds with one stone.
Its pretty heart braking when I lower the water level and see all the scale on my blue crystal pool that is now white.
OH and I agree with You and Scott that it is my lack of maintenance and knowledge that created this scale problem.
 

LauraJ

Gold Supporter
May 23, 2012
16
Tuscaloosa, AL
Re: White scale in fibreglass pool

This problem is the reason (well...one of several) I will never trust a pool store again. They had my pool entered in their computer as being 36,000gallons instead of 10,000. Whenever I'd take a water sample, they always sold me - and told me to use - 3 times the amount of "stuff" that I truly needed. When they couldn't explain to me why I had algae and cloudy water yet my chlorine level was in their "good" range. Their test results showed my CYA was 150+ and FC was 4ppm, but nobody ever said a word about it or mentioned that could be causing my problem. Instead they told me I must have mustard algea and sold me more stuff. that's when I begam researching on my own and found TFP. This site and my test kit have given me more relief and peace of mind than I'll ever be able to express.

I'm clearly no expert at all, so I'm cautious of giving any kind of explanation since I could be completely wrong. But the way I think of CSI is as an overall score to let you know how close to being balanced your water is, and if it's on the acidic or basic side. It's derived from a complicated formula using all the five chemical levels described in this article. pool-school/pool_water_chemistry My test kit has a wheel that I can use to give me the CSI, but now I also have a phone app that makes it much easier.

The good news for you is that you've found the right place to help you fix your current issues and to teach you how to keep others from occurring.
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,083
San Rafael, CA USA
Re: White scale in fibreglass pool

The Pool Calculator will calculate the CSI for you and also help with calculating dosages for individual chemicals and water parameters. The CSI just tells you if the water has a tendency to form scale (when the CSI is positive) or if the water has a tendency to dissolve plaster/grout (when the CSI is negative). You want it in the ballpark near 0, but it's a slow process so is not critical to change unless it's way out of range. If you are seeing scale, then the CSI is probably above +0.7 or so and most likely some combination of pH, Total Alkalinity (TA) and Calcium Hardness (CH) are too high and need to be lowered.
 

nomad26

LifeTime Supporter
Sep 2, 2012
55
Re: White scale in fibreglass pool

Thought I would post a few pictures of my scale to keep this thread alive.
I have read Scotts post a few times and I will read them a few more times again before I try the acid bath on the hot tub
I have been reading about the CSI and trying to let it sink in. Ran my numbers on the pool calculator with my old test kit
it appears I am 0.03 on CSI scale I take all this with a grain of salt because this old test kit is not reliable .
I guess its best to be in the 0 range on the CSI scale not sure I understand the numbers yet . I need to study a bit more.
As soon as the new test kit arrives I will drain the pool to lower the CYA levels
And then go on the Acid bath.
Mark
 

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kalyn2887

New member
Jul 29, 2012
2
Re: White scale in fibreglass pool

I appreciate all the feedback from everyone and the advice Scott. I've posted a picture of mine that shows the white scale buildup (even visible when wet). From what it sounds like, we're probably going to lose the gel coat quality regardless of what we do - buff or acid bath. (yes - I realize it was my own fault that our pool has the white scale) I'm wondering if anyone has experience with using either method and what the outcome was as far as overall fiberglass quality.

Is buffing better or is the acid bath better for the fiberglass coating?
 

Attachments

jjbl

New member
Oct 24, 2012
4
Re: White scale in fibreglass pool

I have been reading the streams concerning the white scale on the fiberglass pools. I too have this problem. My salt cell failed this summer when we had a lot of rain. When it would report that the salt was low, I would add it. In the last month I noticed something different. A white line at the top of the spa when the water would get a little lower from evaporation. I read what many have tried and what "Scott" has recommended. Has anyone tried his solution yet? My stream stopped on September 4th. There is no one within 100 miles of here that knows how to help so I have to make sure the person doing the "fix" knows what to do.
I have removed all the water, the light fixture and niche has been ruined and it covers the entire inside of the spa. I am afraid to leave it dry for fear that it will be worse. Somehow keeping it moist would help??
Scott's solution seems a bit drastic and I am not sure I can do it all. Maybe my only solution is to get rid of it. ;-((((
jjbl
 

nomad26

LifeTime Supporter
Sep 2, 2012
55
Re: White scale in fibreglass pool

jjbl said:
I have been reading the streams concerning the white scale on the fiberglass pools. I too have this problem. My salt cell failed this summer when we had a lot of rain. When it would report that the salt was low, I would add it. In the last month I noticed something different. A white line at the top of the spa when the water would get a little lower from evaporation. I read what many have tried and what "Scott" has recommended. Has anyone tried his solution yet? My stream stopped on September 4th. There is no one within 100 miles of here that knows how to help so I have to make sure the person doing the "fix" knows what to do.
I have removed all the water, the light fixture and niche has been ruined and it covers the entire inside of the spa. I am afraid to leave it dry for fear that it will be worse. Somehow keeping it moist would help??
Scott's solution seems a bit drastic and I am not sure I can do it all. Maybe my only solution is to get rid of it. ;-((((
jjbl
Let me know what you decide . I decided to wait on the process . Mine looks terrible when the pool is drained, with water in it no so bad. I am keeping my ph low and may add scale remover.
Keep me posted
 

UnderWaterVanya

TFP Expert
LifeTime Supporter
Jun 14, 2012
2,589
Mint Hill, NC
Re: White scale in fibreglass pool

nomad26 said:
And here is where you start to lose me.

Check the hardness of the fill water ? That one confuses me . Am I filling the pool with fresh water ?
Yes, as the CH rises (dissolves into the water from the walls) in order to keep the Calcium Scale Index (CSI) negative as the calcium hardness goes up you will need to add fresh water - if and only if - the fill water has a lower calcium hardness than your pool does at the time of the dilution.

nomad26 said:
I am confused with diluting the pool as needed never exceed more then 50 percent at a time ?

I do not have a dry well / sump, I would guess my water levels are low in my area. I live in California in a warm valley, for 5 to 6 months we do not have any rain, when we dug the hole for the pool the soil was very hard clay.
Beyond ground water I think there can be structural concerns.

nomad26 said:
I understand getting the Calcium Hardness level under 300 ppm,
The CSI I need to read up on not sure what that is.
Use www.poolcalculator.com plug in your pool's measured values and the CSI is computed for you. CSI essentially measures the potential for scale to form. If the CSI is 0.6 or higher scale is likely to form. On the other hand if the CSI is below -0.6 then the water is very calcium hungry and can damage tile grout and plaster finishes - or in your case remove scale from fiberglass.

Because the calcium is not destoyed it goes into the water changing the CSI which makes you drain some and refill to get the CSI back on target.

If the fill water has high CH you may have to explore other options.

-sent with Tapatalk 2
 

jjbl

New member
Oct 24, 2012
4
Re: White scale in fibreglass pool

How do you go about changing the CH? What do I add other than water? If I add my well water back to the pool, and do not run it through the "salt cell,"
will that make a difference? Is there a chemical that is available that lowers calcium?
 

UnderWaterVanya

TFP Expert
LifeTime Supporter
Jun 14, 2012
2,589
Mint Hill, NC
Re: White scale in fibreglass pool

jjbl said:
How do you go about changing the CH? What do I add other than water? If I add my well water back to the pool, and do not run it through the "salt cell,"
will that make a difference? Is there a chemical that is available that lowers calcium?
The answers I have seen here are:

Change some/all of the water.
Change some/all of the water.
Change some/all of the water.
(or if you live a very small part of the country - reverse osmosis - but this is often not cost effective compared with - you guessed it "change some/all of the water".)

No - Salt Cell isn't what is causing this. Calcium Hypochlorite (a powdered chlorine without CYA) can elevate these levels but given where you live (CA right?) it's probably in the fill water and as your water evaporates the concentration goes up. Several people have shared their strategies - dumping water periodically to waste to water the lawn, etc. Essentially if the fill water is high - the pool will be even higher unless you have not yet had any evaporation.