Calcium Removal from Pool Water to Address Water Line Scale

[Midnight]

UPDATE
Glad to report that the process worked out perfectly!

CH is down to my target 200 from about 600, somehow I nailed it maybe through dumb luck? I added enough PH up until it got below my target so maybe I can take some credit.
Tiles on the spillway already look way better even before doing any cleaning. It seems the lower CH water has dissolved away some of the excess calcium. A layer of hard baked on calcium remains though.
I was able to use a pool vaccum attached to the skimmer to suck out almost all of the CA precipitate.
I used a full bucket of PH increase which is 18 lbs.
Used 1.5 gal of Muratic Acid to get it back to 7.2PH
I did check the CH in the water after the CA settled and it was 125. After vacuuming some is left and so adding this back in when dissolving by decreasing PH brought it up 200. SO, best to get it a bit under your target before raising PH back up.
I did have to wash out my cartridge filter which had a decent amount of CA in it, but was not caked or clogged, pressure only went up about 5 PSI. But it was definitely enough to warrant a good cleaning instead of washing it all back into the pool.
See some updated pictures at the bottom of the thread.

__________

After fighting the past 3 years with calcium build up on the pool tiles at the water line, I decided to try and reduce the CH in the pool water.

Background
When I had a "professional" pool service doing my new pool for the first year, I noticed scale building up on the tiles. I checked the CH and it was 1275, way over the CSI limit. So I fired them and decided to learn what I needed to get the pool properly balanced. The next 2 years it has still had issues even after getting the CH lower.

Initially I did a drain and fill a few times and got CH down to around 600. But this didn't fix the calcium building up.

Recently I again tried doing a couple of 1/3 empty & refills on the pool which did help but only got the CH down to about 575, which is surprising as the tap water CH is only 125. I was expecting to get CH down to 300 or so. CH is generally around 600-700 most of the time. It is lower when I do a drain-fill, but never gets below 575, usually in the 650-675 range. Apparently this is within limits, however I still get a lot of calcium build up along the water line, so it seems not good enough. I'm not sure why it stays above 600 all the time, except maybe the CA is still leeching from the plaster. I thought after 3 years this would be mostly done with. So this whole thing may be a fruitless effort if CA leeching continues and the CH goes right back up to 600+. We will see.

The PH often goes over 8.2 which can increase CSI too high and cause scaling. While I try to add acid at least weekly, it is constantly going over the limit. It pobably goes up .2-.4 per day. It uses a LOT of acid for 8k-10k gallon pool. About 1/3-1/2 gallon per week of muratic acid. Not sure why this is. I have 120 TA so it seems it shouldn't bounce that much? I also have a rather large spa to pool spillway which I understand increases the PH with more air turbulence surface area.

I did a test on a glass of pool water. It worked great, getting CH down to 0-10 range, basically the test sample was blue immediately indicating no CA, didn't have to add any drops to measure it.

I have a large tile spillway from the spa which is in dire need of cleaning to get it back to pristine beautiful condition.

The Fix Attempt
I added about 5 lbs of PH increaser to the pool to increase the PH very high which makes the calcium precipitate and turn into a fine dust which can be (hopefully) vacuumed out of the pool. Not sure exactly how high the PH is, 9.5-11 maybe, can't measure it precisely that high.
I checked the CH and it only went down to 525 from 575. A bit surprised it is still that high with so much CA precipitated already. Possibly the PH is not high enough and there is still a lot of CA in the water.

To vacuum out the CA I'm going to attempt to use a sump pump I have on hand for flushing my hot water heater (coincidentally to also revmove CA scale).
If that doesn't work well enough I will use the pool pump with the pool vacuum attachment, however it goes straight to the filter and there's no backwash capability on my system so I may just have to leave the filter open and let the water drain wherever it goes, otherwise I think most of the CA will simply be pushed through the filter and back into the pool again. It is a very fine powder similar in consistency to Diatomaceous Earth, so I have to dump the water down the drain to get rid of it.

After removing the CA I will add gallons of acid back to bring the PH back to 7.4 and dissolve any remaining CA. In my test with a glass of water this worked out beautifully.

The next day the water level had dropped by 5" in the pool and 2" in the spa. Not sure why execept evaporation? Seems very odd.


Removing Waterline Scale
I have already tried a few options to remove the scale, so far nothing has worked very well.

• Scraping with a kitchen knife - worked pretty well, but took several hours just to do the spa only, and it was only 90% better.
• Using diluted muratic acid - didn't do much.
• Using full strength muratic acid - worked somewhat, but not completely and ate away grout, loosening tiles.
• Using some water line scale remover product - didn't do anything at all.
• Using muratic acid with a metal brush - didn't do much better than kitchen knife, scratched up the tiles some
• Using pumice stone - destroyed the glass tiles really bad. lol. I will replace them at some point.

Some things I'm going to try still

• Using a dremel and some various bits to see if any can remove the scale while leaving the glaze on my glass tile intact.
• Using a soda blaster - Gravity Feed Abrasive Blaster Gun with 20 oz. Hopper

Pool Details
10k gallon
Saltwater
Plaster (pebble tech)
Tap water is 450 TDS, 125 CH
CH avg 575-675
Glazed Glass tile

Pictures

Added PH increase.


Next day the water dropped 5-6". Why?


Water was at the tile line, now 5" lower. Also you can see the CA on the step. Don't worry it washed off easily.


The bane of my existence.




The spillway is a disaster. It looks much better when wet but you can see the obvious buildup that makes it look hazy even when wet.



I had already used Calcium release, vinegar and muratic acid on this section. It keeps coming back within 2 weeks.


Can see how milky the water is, CA precipitated



Here you can see the water line scale build up.



Can barely see the towel I used to plug up the water fill inlet.


Next day the water level dropped, but also water is much more clear.

 

[AQUA~HOLICS]

Two suggestions:
Glass beading to remove the calcium.
Pool Tile Restorer is pricey but it works.

 

[Rancho Cost-a-Lotta]

Check out the link below. Similar method you described:

Reducing High Calcium Levels in Pools

Many of us may have had the unfortunate experience of adding soda ash to raise the pH and turned the pool water a milky white… in fact, we refer to it as “milking” a pool. Why does that happen and what does that do to the water? Well, the soda ash (sodium carbonate) is normally very soluble in...

www.troublefreepool.com

The best way to reduce/eliminate calcium rise in a pool is to top-off using softened fill water. Do you have access to softened water in the home? If not, consider a smaller automated water softener dedicated to the pool, or a portable RV water softener (link in my sig).

 

[Rancho Cost-a-Lotta]

A few years ago, I paid for glass bead blasting to remove the waterline scale. At the time, cost was $4 per liner foot.

Waterline Scale Removal - Further Reading

www.troublefreepool.com

 

[Midnight]

A few years ago, I paid for glass bead blasting to remove the waterline scale. At the time, cost was $4 per liner foot.

Waterline Scale Removal - Further Reading

www.troublefreepool.com

I may look into a professional service. I have an air compressor already, so I might be able to do it myself with just a blaster unit such as this one for $22.


I need to add a bit of TA anyway to combat PH crazy swings (going to shoot for 150-170? from 110) so I was thinking to try bead blasting but using soda (aka baking soda) and some of it will fall in the pool and raise the TA while I work
Apparently it is prescribed for just this purpose. But, I do think soda may not be strong enough and need to go with glass beads. Won't hurt to try it first though.

This image from harbor freight tools indicates various bead blasting setups. As you can see cleaning pool tiles is listed under soda blasters.

 

[mknauss]

To lessen your pH rise, you need to lower TA to under 80.
I suggest you read Pool Care Basics

 

[Rancho Cost-a-Lotta]

I need to add a bit of TA anyway to combat PH crazy swings (going to shoot for 150-170? from 110) so I was thinking to try bead blasting but using soda (aka baking soda) and some of it will fall in the pool and raise the TA while I work

According to one of our experts, baking soda doesn't have the hardness necessary to remove calcium scale. Read this post, also included in the waterline scale article:

Waterline Scale Removal

After a recent drain and refill and dialing in my chemistry and CSI, I'm ready to have the waterline calcium scale removed. I now understand how to avoid calcium deposits so I'm ready for a nice clean start. As I start my search of local vendors, I thought I would seek input that may help me...

www.troublefreepool.com

The two most common types of media used are glass-beads and kieserite. Kieserite can add sulfates to the pool that can cause damage to metal and plaster surfaces. Glass beads are vacuumed up by the service provider after the process is complete.

 

[Midnight]

Two suggestions:
Glass beading to remove the calcium.
Pool Tile Restorer is pricey but it works.

I have that as well as their calcium release (which is what I think you meant to remove the scale?). It does work ok but needs multiple applications and scrubbing which I haven't really gotten into yet, I did try applying it 4x on a patch of tile and it did loosen up some but will need manual effort as well. Hoping to use that and the other products to maintain the tile and keep calcium from sticking as much.

 

[Midnight]

To lessen your pH rise, you need to lower TA to under 80.
I suggest you read Pool Care Basics

Thanks, Guess I had it backwards. I did have TA down around 70 for a while and I think PH still rose quite fast, but maybe it's worse now and I don't realize it.

 

[JoyfulNoise]

I suggest you stop creating milky water unless you want to wreck your pool surface. Intentionally precipitating calcium carbonate scale is dangerous to do in a plaster pool as you cannot control where the calcium will scale. Yes it will create some precipitates in the water volume but it will preferentially find other porous surfaces to grow on and your pool plaster is perfect for that. You also cannot soften water appreciably that way. Lime softening is a process that uses calcium hydroxide and sodium carbonate to create the pH necessary to create calcium scale Washing soda by itself is not alkaline enough to precipitate calcium carbonate. Most of the precipitate you are seeing is likely magnesium hydroxide as that is the first mineral precipitate to form at lower pH (around 10.5-11)

You can not lime soften pool water. The pH is too high and the neutralization with acid will cause the waters salinity to rise by quite a bit. The best way to reduce CH is through draining and refill. Your previous attempts at that should have worked and so there probably was some measurement errors in what you were seeing with the CH not dropping. A properly executed exchange-drain can easily reduce CH to the level of the fill water CH. Just doing blind draining and refill causes the law of successive dilutions to come into effect which reduces the efficiency of the CH reduction.

 

[Midnight]

Thanks, Guess I had it backwards. I did have TA down around 70 for a while and I think PH still rose quite fast, but maybe it's worse now and I don't realize it.

To lessen your pH rise, you need to lower TA to under 80.
I suggest you read Pool Care Basics

Hmm so actually per the pool test kit it says to raise TA to provide more stable PH, which is where I had that in my mind from.

 

[Midnight]

I suggest you stop creating milky water unless you want to wreck your pool surface. Intentionally precipitating calcium carbonate scale is dangerous to do in a plaster pool as you cannot control where the calcium will scale. Yes it will create some precipitates in the water volume but it will preferentially find other porous surfaces to grow on and your pool plaster is perfect for that. You also cannot soften water appreciably that way. Lime softening is a process that uses calcium hydroxide and sodium carbonate to create the pH necessary to create calcium scale Washing soda by itself is not alkaline enough to precipitate calcium carbonate. Most of the precipitate you are seeing is likely magnesium hydroxide as that is the first mineral precipitate to form at lower pH (around 10.5-11)

You can not lime soften pool water. The pH is too high and the neutralization with acid will cause the waters salinity to rise by quite a bit. The best way to reduce CH is through draining and refill. Your previous attempts at that should have worked and so there probably was some measurement errors in what you were seeing with the CH not dropping. A properly executed exchange-drain can easily reduce CH to the level of the fill water CH. Just doing blind draining and refill causes the law of successive dilutions to come into effect which reduces the efficiency of the CH reduction.

Interesting, thanks for the info. I read somewhere else on this site that magnesium precipitates out at higher PH so it's hard to get out of the water so have to use harsher calcium hydroxide to get the PH that high, otherwise with sodium carbonate you only get calcium to precipitate? I am not an expert on this so don't claim to know.

My "kitchen" testing showed that this approach worked well to remove calcium. Perhaps that level of sodium carbonate vs water was more concentrated so gives different results?

 

[Midnight]

Glad to report that the process worked out perfectly!

CH is down to my target 200 from about 600, somehow I nailed it maybe through dumb luck. Tiles on the spillway already look way better even before doing any cleaning. It seems the lower CH water has dissolved away some of the excess calcium. A layer of hard baked on calcium remains though.

I was able to use a pool vaccum attached to the skimmer to suck out almost all of the CA precipitate.

I used a full bucket of PH increase which is 18 lbs.
Used 1.5 gal of Muratic Acid to get it back to 7.2PH
I did check the CH in the water after the CA settled and it was 125. After vacuuming some is left and so adding this back in when dissolving by decreasing PH brought it up 200. SO, best to get it a bit under your target before raising PH back up.

I did have to wash out my cartridge filter which had a decent amount of CA in it, but was not caked or clogged, pressure only went up about 5 PSI. But it was definitely enough to warrant a good cleaning instead of washing it all back into the pool.

 

[Midnight]

 

[JoyfulNoise]

While I certainly would never attempt this process in my own pool (too much possibility in damaging expensive equipment), I’m glad it worked out for you in the end. Water is expensive here in Tucson but it’s a lot cheaper to drain and refill my pool (maybe $200 total), then to risk damaging thousands of dollars (pump, heater, SWG) in equipment or risk damaging my plaster.

I will note one thing though - you need to do a bucket test and check your pool for a leak. It appears from what you posted that you lost 5-6” in less than a day. That is not normal at all even when evaporation rates are high. Unless you can find a better explanation for that much water loss, I’d do a bucket test.

 

[Midnight]

While I certainly would never attempt this process in my own pool (too much possibility in damaging expensive equipment), I’m glad it worked out for you in the end. Water is expensive here in Tucson but it’s a lot cheaper to drain and refill my pool (maybe $200 total), then to risk damaging thousands of dollars (pump, heater, SWG) in equipment or risk damaging my plaster.

I will note one thing though - you need to do a bucket test and check your pool for a leak. It appears from what you posted that you lost 5-6” in less than a day. That is not normal at all even when evaporation rates are high. Unless you can find a better explanation for that much water loss, I’d do a bucket test.

It only did that on the first day. Not sure what happened, but I did accidentally leave the drain valve open on the pool equipment, however it is above the water level so can't figure out how it could have drained out. It only drains some water when the pump is on, and the pumps weren't running. But yes thanks for the tip. I may plug up the autofill again and make sure it's not draining, but I'm 99% sure it was a fluke of some kind.

 

[Midnight]

While I certainly would never attempt this process in my own pool (too much possibility in damaging expensive equipment), I’m glad it worked out for you in the end. Water is expensive here in Tucson but it’s a lot cheaper to drain and refill my pool (maybe $200 total), then to risk damaging thousands of dollars (pump, heater, SWG) in equipment or risk damaging my plaster.

I will note one thing though - you need to do a bucket test and check your pool for a leak. It appears from what you posted that you lost 5-6” in less than a day. That is not normal at all even when evaporation rates are high. Unless you can find a better explanation for that much water loss, I’d do a bucket test.

Also, do you know if it is ok to fully drain the pool then refill? I've been doing 1/3 refills because I read that draining it completely may cause it to pop up out of the dirt depending on something like maybe how wet the dirt is or just how it settled, they didn't explain it. Also any effect on the plaster being exposed for a couple days? I don't think so after it is cured.

 

[mgtfp]

Hmm so actually per the pool test kit it says to raise TA to provide more stable PH

Higher TA means more pH buffering against pH dropping from using acidic forms of chlorine such as Trichlor. The downside is, that by adding baking soda you oversaturate the water with CO2 which wants to outgass, increasing pH in the process. For non-acidic chlorination methods like liquid chlorine and SWGs, you don't need much buffering against pH dropping, and it is more beneficial to run a lower TA to minimise pH-rise by CO2 outgassing.

I used a full bucket of PH increase which is 18 lbs

You were very lucky that you didn't have metals in your water, or you could have ended up with a massive metal staining problem. Plus all the problems that Matt already pointed out.

I wouldn't recommend that method as a general cure, there is a high risk that it created more (and more expensive) problems than the initial problem. Glad it worked for you, though.

 

[AQUA~HOLICS]

Also, do you know if it is ok to fully drain the pool then refill? I've been doing 1/3 refills because I read that draining it completely may cause it to pop up out of the dirt depending on something like maybe how wet the dirt is or just how it settled, they didn't explain it. Also any effect on the plaster being exposed for a couple days? I don't think so after it is cured.

This pool was constructed during the winter of 2018 and SoCal received over 15” of rain that winter. Personally have never seen one first hand during construction process with a empty shell.
Keep the time to a minimum of air and sun exposure on the plaster. Most common side effects of over exposure is delamination between plaster coats/layers that may occur.

 

[Midnight]

Higher TA means more pH buffering against pH dropping from using acidic forms of chlorine such as Trichlor. The downside is, that by adding baking soda you oversaturate the water with CO2 which wants to outgass, increasing pH in the process. For non-acidic chlorination methods like liquid chlorine and SWGs, you don't need much buffering against pH dropping, and it is more beneficial to run a lower TA to minimise pH-rise by CO2 outgassing.


You were very lucky that you didn't have metals in your water, or you could have ended up with a massive metal staining problem. Plus all the problems that Matt already pointed out.

I wouldn't recommend that method as a general cure, there is a high risk that it created more (and more expensive) problems than the initial problem. Glad it worked for you, though.

I have a SWG. After this experiment the CL was at 0, so I ran the SWG for 8 hours and got the CL up to 7PPM. This also increased the PH from 7.4 to 8.4. Any idea why that is? I'm using about .4 gal of muratic acid a week to keep PH in check. TA is ~115

I'm considering to get a CO2 automated system to keep the PH at the right level. These PH swings make it very difficult to keep it in balance and avoid calcium deposits. I thought with a SWG I would have very little chemical maintenance needed, not the case. I'm probably spending more on MA than I would be just adding CL directly. (BTW, the price locally has gone from $11 to $17 for 2 gal recently)

Shouldn't the TA be going down over time given I'm dumping a gallon of acid in every 2 weeks?

Thx for your help.