Low pH /Scale Control Product

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spoonman

spoonman

Well-known member
Jun 16, 2016
431
Peoria, AZ
Hi folks

I’ve had some tile scale due to managing excessively high CH (1425 currently). As part of resolving this, I’m about to have RO done on my water soon to remove the calcium.

Before I do RO I want to tackle the water line ring. Today I added Bio-Dex Protect All, which is supposed to reduce or eliminate waterline scaling (or soften it for cleaning) within 48 hours.

Before adding Bio-Dex, my TA was 50 and pH 7.4. After adding my TA is 40 and pH looks to be around 6.7 (guessing as it is below 7.

I’m a bit concerned about the low pH, but think it may be OK for a day or two. Should I let this product run its course, or should I be concerned about the low pH?
 
Another update. I checked the pH this morning and it is already up to 7 overnight. I’m going to leave the pool alone and let it come back on it’s own. Knowing my pool it will be 7.2+ by this afternoon.
 
I feel a lot better about it with pH at 7.0 or higher. The problem with guessing at a pH when it is above or below the range is that it could be much higher or lower than the guess or what it "looks like". TA being 40 helps to know that pH is not very low. If TA had been lower it would have been a bigger concern that pH was also lower.

I have successfully removed a scale ring around the tile by lowering the CSI In the pool down to -0.6 to -0.8. Mine dissolved and goes awat on its own. PoolMath will calculate your CSI for you after you eneter all your test results, including water temp. With your CH being very high it is more important to look at your CSI and keep it between -0.6 and +0.6 to prevent scaling.

More here, Pool School - Calcium Scaling
 
How long did it take at -.6-.8 CSI to dissolve your calcium ring? I know it would be ideal to stay slightly negative all the time but that is a bit challenging with excessive CH levels. After the RO treatment (targeting around 200 down from 1425) life should get a bit easier.
 
Less than a week. Sometimes I would go around the pool and rub it with a nylon brush or my finger if I was bored in the pool. That was before I learned about CSI now I keep it around -0.3 and haven't had a ring in years. Yes, much more difficult to keep CSI negative with CH above 1000 or 1200. That's when most of the "high CH" folks give up and do a partial drain and refill. I would expect RO to power CH more than that. I've seen folks do RO and it seems like they had better results. Can't remember for sure though.
 
Using pool math, it is not feasible with a CH of 1425 to get to -0.6 or -0.8 CSI (level PoolDV used to remove scale) without taking the pH down to 6.8. Best I can do without destroying the pool is to hold the pH at ~7.2 (CSI of -0.28) to help reduce scale, though this seems futile as -0.28 CSI will likely not have a significant impact on scale within a week or two.

It may be best to remove the scale after RO is done on my pool. PoolMath says with a CH of 225 (my RO goal), TA of 50 and pH of 7.3, I can hit -0.77 CSI. Seems like my best course of action it to try another bottle of calcium remover + scrubbing before RO is performed. If I have any more calcium ring I can try to combat with low CSI after RO when I'm able to reach lower CSI values.

Any suggestions here?
 
With no heater and very high CH you aren't going break anything in your pool by running your pH down to 6.8 for a week or two.

Low pH, below 7.0, causes two main problems in pools.

First, pH below 7.0 is corrosive to metals. It will dissolve copper, such as in heat exchangers, over time.

Second low pH, below 7.0, can contribute to a condition called etching. Etching is when the water becomes aggressive and leeches calcium from the plaster. But your very high CH will offset any potential issues with etching. And etching is a long term problem over many months or more, not a couple of weeks.

What is in that calcium remover? It may just be some type of acid that lowers the pH anyway.

If you want to work directly on the ring you can dilute 1 part muriatic acid into 2 to 4 parts water in a spray bottle and spray the ring and brush it. Some people like to float around their pool and do that. :)

Gloves and eye protection recommended. Always add acid to water, never add water to acid.
 

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Good info DV. Thanks.

I should mention that I do have a pool ladder that is stainless steel. Not sure how big of a concern this will be. It can be removed though if needed.

Using diluted acid sounds like the way to go. Especially with a spray bottle. As an aside, I’ve been curious if there is a known recipe that may include mixing the acid with soap in order to make it more gelatinous and spreadable on the tile so it can sit for longer periods.

The scale remover is ~40% citric acid, plus unknown proprietary and trade secret ingredients. As of today (almost 72 hours) it appears to have done very little.
 
Yes, so they are using citric acid to lower the pH to help dissolve the scale. Using CSI to lower it is much more accurate. I haven't heard of using a thickener to help the acid stick to the tile. That's a pretty good idea! I wouldn't be too worried about the stainless steel ladder for a week or two, it is much more robust than copper.
 
Gotcha. Thinking I’ll stay the course on very low CSI for a few more days, then try cleaning by hand. I did raise up my waterline before starting this project. Hoping that will make scrubbing the scale easier once I drop back down to clean.

I should mention that the scale remover seems to be eating all of my chlorine. There is zero chlorine in the pool yesterday and today. Sample won’t turn pink.

Should I just keep dosing until I get the correct reading, or shock the pool?
 
Keep dosing. Maybe dose to halfway between target and shock level. I know ascorbic acid will use up FC but I don't know if citric acid does. I guess we know now that it does. Unless it is one of those secret sauce ingredients in there.
 
Citric acid is like ascorbic acid, they both neutralize chlorine. The BioDex product did mention this (albeit not in a very meaningful way). I would not add soap to MA, that could cause polymerization and hardening of the soap. You can try to use some of the BioDex tile cleaning products as they are similar to Lysol Advanced Toilet bowl cleaner (12% MA with thickeners). Some of those tile cleaning products contain phosphoric acid and hydrofluoric acid, so be very careful when using them (rubber gloves, eye protection).

Good luck with the RO. Let us know how far they get.
 
Must eat the chlorine up quickly too. I have a Stenner pump that doses about 18oz of chlorine daily and it doesn't even register. Before adding in the Bio-Dex, I was holding steady at around 6ppm FC. Makes me wonder how long the citric acid will have this effect. That's what I get for pouring junk into the pool. Worst case the RO will filter this out. I'm scheduled to have that done in 2 weeks.
 
spoonman said:
Must eat the chlorine up quickly too. I have a Stenner pump that doses about 18oz of chlorine daily and it doesn't even register. Before adding in the Bio-Dex, I was holding steady at around 6ppm FC. Makes me wonder how long the citric acid will have this effect. That's what I get for pouring junk into the pool. Worst case the RO will filter this out. I'm scheduled to have that done in 2 weeks.
Click to expand...

The reaction is practically instantaneous. The chlorine and citric acid neutralize one another so as soon as all of the citric acid is used up, the FC will begin to hold again. Careful to not let it sit at low FC for too long or else you'll get an algae bloom.
 
Good info. Sounds like I can chlorinate myself towards lower citric acid levels since they neutralize one another :goodjob:

Any idea why citric acid would be used instead of MA in a product like this? Perhaps citric acid is less reactive with the other ingredients, or holds pH lower, longer?

Edit: I recall that the Bio-Dex product is also supposed to help with "stains", which could be partly the reason for citric acid.
 
spoonman said:
Good info. Sounds like I can chlorinate myself towards lower citric acid levels since they neutralize one another :goodjob:

Any idea why citric acid would be used instead of MA in a product like this? Perhaps citric acid is less reactive with the other ingredients, or holds pH lower, longer?

Edit: I recall that the Bio-Dex product is also supposed to help with "stains", which could be partly the reason for citric acid.
Click to expand...

If it were just muriatic acid, they couldn't charge you the premium they do :deal: Also, citric acid is a lot safer than muriatic acid to ship and sell.

Citric acid is not nearly as acidic as MA but it does partially chelate metals so it can temporarily remove stains. It helps to make calcium more soluble in water BUT, once the chlorine destroys it, all of that chelating effect is lost. So, honestly speaking, it's not a very good product for scale removal or control in a chlorinated swimming pool.

Once your CH has been lowered, you can tackle waterline scale by raising the water level and lowering the CSI as Danny suggested. But do note - your CH will increase as calcium will be removed from ALL surfaces, not just the water line ring. Since you're up in Peoria, give Mark White at Arizona Bead Blasters a call or e-mail and ask him if he can soda blast your tiles before RO. He uses kierserite blasting (MaxxStrip is the product line) and it effectively removes calcium scale because it's hardness is exactly matched to that of calcium carbonate. It removes scale without any damage to the tile glaze. He did my pool about 4 years ago and it looked like it was brand new after he was done. Unfortunately he doesn't service Tucson anymore (not enough business to justify the drive down) so I'm out of luck but I would use his services again in a heartbeat.
 
Quick update. My pool is now holding chlorine again, so presumably the citric acid has been used up.

I still have a bit of a calcium ring, but I’m not sure it is bad enough for me to invest in professional cleaning...at this point anyway. Kiersite sounds like the way to go...just not the sealer from what I’ve heard.

Think I’m going to keep the CSI very low a few more days and give it a scrubbing before doing RO. Think I should get the bulk of it this way.
 

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