Continued Very Low Calcium Hardness Issues

by Deb
(North Dakota)

We have a fiberglass in-ground pool, total of 34,000 gallons. This year we had water trucked in as our fill water is high in iron. This was soft water, fill water had CH of 25. We have added a total of 150 pounds of calcium carbonate from the pool store over the past 2-1/2 weeks.


This morning, our calcium hardness is back down to 21. The highest it has reached is 61. I do add muriatic acid at least weekly to keep my pH at 7.2 due to adding fill water from our well after backwashing.

We have a clear pool, but am concerned why I keep losing the calcium I have added and am unable to get the CH level up to at least 150. Does muriatic acid or chlorine lower this level? Have had this pool for 13 years and this is the first time I have spent lots of money to have city water trucked in which has caused this new issue for us. Our fill water from our well has a CH level of 64.

Did I mention we live in North Dakota, so have a lot of rain issues this fall. Am currently not heating the pool at this point, so no issues with running the soft water through our heater. Use a sand filter.

Thanks for your thoughts on this question. We use a ColorQ test kit for all my levels.




Thanks for the question Deb

LaMotte ColorQ test kits are alright but I'd encourage you to look into the Taylor K-2006 kit. It's more accurate. A bit of getting used to but worth the investment.

Next is the use of calcium carbonate. This is added as a pH corrector and to maintain alkalinity. I think what you actually want is a product called calcium chloride or calcium chloride dihydrate. These will raise the hardness. Dow Peladow calcium chloride is good and relatively inexpensive at 38 cents per pound.

You don't need to be concerned with the hardness too much with a fiberglass pool. Hardness is mainly for plaster pools. This is because the water will pull the calcium carbonate from the plaster and cause pitting. Having a hardness level of 50 - 100ppm for a fiberglass pool is good enough.

To post a reply, or if you have a similar question, you can see your post on the Q&A page in the "Calcium Hardness" category.

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Hope this helps and have a great Summer.

Robert

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White Flakes From Pool Return Clogging SWG?

by Elle
(Modesto CA)

I have a aqua rite salt water generator. My pool is about 13,000 gallons with a raised spa. I have included as much info as possible. I don't know my calcium hardness but I can tell you that our water is very hard. I live in the Central Valley of California. Here is my situation:

6-13-14. Everything with SWG was working fine. Salt level was 3000
6-14-14 Had a pool service remove buildup from our tile line in both the pool and raised spa. This created a lot of cloudiness/debris for a couple days.
6-19-14 Same guy came out and cleaned the filter and cell.
6-19-14 to 7-3-14 Noticed a lot of white flakes coming out of pool returns.
7-5-14 Salt down to 2600 flashing low salt and check cell
7-5-14 I opened up the cell, a good amount of junk in there. Cleaned it and when I started up SWG again reading went back to 3000.
7-6-14 I turned my filter on manually and a TON of white flakes came out of pool return when the SWG started generating. Salt heading back down to 2800 even after I added about a third of a 40 lb. bag.

So... at first I thought the pool service guy did not clean the cell (but I've known him a while and he is a stand up guy so that didn't make sense.) I
My next suspicion is that all the calcium hardness that was scraped off my tile is now "swimming"around the pool and settling in the cell when the system shuts off. It seems to build quickly and make my cell go into shut down mode once it is sufficiently gunked up.

Has anyone had this happen? Am I on the right/wrong track? What is the solution?

My numbers yesterday were:
FC 4.0
TA 90
PH 7.8
CYA 110

Today my PH is down to 7.6 and FC is at 5.0.




Thanks for the question Elle

I'm going to try to break this down as best I can. First is your pH. It's a bit too high at 7.8. You want to try to keep it at 7.4 - 7.6. This will be more difficult with a CL generator as they tend to increase the pH at a slightly faster rate.

The white flakes that you're dealing with is more certainly the calcium carbonate after the cleaning. If your CL cell is reverse polarity then one side is being cleaned while the other side is producing CL. The flakes are then coming off into the water. Living in CA with hard water is something you can't get around unless you have pool water trucked in. Be sure you're not using granular chlorine (calcium hypo). This will not only raise the pH but add hardness to the water.

Next is your CYA. It's a bit high at 110ppm. Normal range is 30 - 50ppm. There's no way to reduce that but to do a partial/full drain and refill. You're running the risk of having a green pool with a CYA that high. But on the bright side you can have a slightly higher CYA with a salt pool when you allow the TA to come down to 70ppm and keep the CL between 4 - 5ppm.

You might want to consider adding borax to 50 ppm to your water. This acts as a secondary pH buffer and has been found useful with CL cells. It's 113 oz. of borax to raise the level 10ppm per 10k gallons. This is nothing more than 20 Mule Team Borax than can be found in the grocery store. The reason it's good with CL cells is because of the out-gassing that precipitates the pH rise with a CL cell.

You'll need to have muriatic acid on hand as adding borax does raise the pH in the pool but the borates remain as a buffer. If you choose to do this remember to make small adjustments rather than on large one. It's 20 oz. of acid to lower the pH 0.2 per 10k gallons. Remember that when you add the acid it will hit both the TA and pH. The CL cell will naturally increase the pH.

So to sum it up I'd reduce the TA to 60 - 70ppm. Normal range is 80 - 100ppm but a salt pool can get away with a slightly lower TA. Keep the pH 7.4 - 7.6 and no higher. Add enough borax to bring the level up to 50ppm, keep the CL generator clean and FILTER and BACKWASH when needed.

I hope this has answered your question to your satisfaction.

To post a reply, or if you have a similar question, you can see your post on the Q&A page in the "Calcium Hardness" category.

Check back to this post for updates or answers.

If you feel your situation is more complex and want immediate assistance (within 24 hrs) you can make a donation of your choice and I'll answer your questions by phone.

Have I helped you find a solution to your pool problems? Did this information help you? Please consider making a donation to help keep this site going. Thank you.









Have a great Summer.

Robert

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Salt and Hardness

How does salt contribute to total hardness? Is there a formula for subtracting salt as hardness?




Thanks for the question

Salt does contribute to the total hardness of the water. This is commonly known as TDS, or Total Dissolved Solids. My own personal feeling is TDS is essentially useless because it doesn't tell you what's in the water.

Here's a good post on that:

http://ppoa.org/pdfs/What%20is%20the%20Fuss%20Over%20Total%20Dissolved%20Solids.pdf

There could be hundreds, if not thousands, of different solids in the pool water and would be cost prohibitive to run a slew of tests to find EXACTLY what's in the water. It's the makeup of the TDS that is important, not the TDS itself. TDS is usually mostly salt due to pool owners using liquid chlorine (sodium hypochlorite) and baking soda (sodium carbonate and bicarbonate), calcium chloride, etc...

TDS is a useful measurement for determining the Calcium Saturation Index but that's about it.

I can tell you some of the main solids are:

  • Lead
  • Copper
  • Iron
  • Salt
  • Manganese
  • Calcium

    Virtually everything that goes or falls into the pool contributes to the TDS rising.

    I think the 2nd question has been answered, but again, I'm not aware of any specific formula that you can calculate the amount of TDA or hardness minus the salt.

    Most of the time pool stores will tell you to drain and refill the pool when the TDS gets about 1500ppm. I'd suggest looking at the post above and formulating your own opinion.

    To post a reply, or if you have a similar question, you can see your post on the Q&A page in the "Calcium Hardness" category.

    Check back to this post for updates or answers.

    If you need immediate assistance (within 24 hrs) or for emergency personal assistance, you can make a donation of your choice and I'll answer your questions by phone.

    Contact Me

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    Hope this helps.

    Robert

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    Our Pool Tested 0 On The Total Hardness Scale

    by Jake
    (Houston)

    Our kids went swimming before I tested the water and all 3 of them got sick (Stomach Aches) Could the low Total Hardness really be the cause of them getting sick?




    Hi Jake. First we need to define our terms. TDS or Total Dissolved Solids is the make-up of all the solids that that can be found in water. It's very difficult to determine what that make-up is. Calcium hardness one one of those factors. That is mostly for plaster pools to lessen pitting and etching of the plaster.

    There could be one or a combination of things to consider. The FC must be kept between 2 - 4ppm in order to kill the organic matter in the pool. If there's not enough chlorine and your kids swallow the water, there is a chance they can become sick. This is known as water-borne illness. I had to become very familiar with this when I was the pool operator for the YMCA.

    Next is simply swallowing too much water. This is also dangerous as it can cause "dry drowning". This occurs when one swallows too much pool water. The person can become lethargic and sleepy, vomits up the water and chokes.

    I would suspect it could be lack of chlorine and/or swallowing pool water, something that is never recommended. I would check the FC and adjust to 2 - 4ppm and advise your kids to never swallow any kind of pool water. If any symptoms get worse it's best to be checked out by your doctor.

    Please understand this is not meant to be medical advice. They're simply my experiences and for informational purposes only.

    Robert

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    Calcium Hardness Too Low

    by Elizabeth
    (Kilgore, Texas )

    We just recently installed a 18x48 Intex pool. We just added the salt and started the sand filter today but have NOT started the salt water system yet. My test strips are showing low calcium hardness as well as low free chlorine. Is this due to the salt water system not being hooked up yet? If not, what would be the solution to this problem? Also, it has been raining here all day! Thanks in advance!




    Hi Elizabeth. No chlorine would be a result of not having the chlorine cell up and running. It may take come time to dial it in correctly to your particular usage. Keep adjusting until you get it right for your pool. Be sure to get the CYA/stabilizer in there as well. Your salt pool can run the CYA around 50 - 60ppm.

    Hardness is more for plaster pools. The range is 150 - 250ppm but you always want to follow the manufacturer's instructions. I wouldn't go over 2500ppm due to the cell may calcify and compromise the chlorine output. If the CH is low you can add calcium chloride. Very easy to do.





    Robert

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