The next time you’re in your swimming pool reach down, grab a handful of water and squeeze your fingers together. Hard water will fall and break apart. It’s thin with no consistency but Soft water slides out, feels soft, silky and you can see and feel the difference. How do you make the water in your swimming pool soft, and silky smooth?
- By dropping levels of Calcium dissolved in the H2O using Muriatic Acid,
- Take Calcium out of solution by Raising pH & Alkalinity to 10 pH in warm temps.
- Add Flocculant
- Let pool Sit
- Vacuum floc to waste
- Lower Alkalinity, pH with Muriatic Acid
The terrible things that you read on the internet about how Hard or Soft water can ruin your swimming pool, all can be controlled by adjusting pH & Alkalinity. You can get that Satiny look and feel without taking your water out of your pool or your wallet out of your pocket. But Sorry guys, you got know how it works, first.
Hard Water in Pools
The ideal level for Calcium Carbonate Hardness is between 200-400 mg/l in a Cement or Concrete pool. 80 to 150 mg/l in a Vinyl pool or 150 to 250 in a Fiberglass pool. You can run it at higher levels while taking some precautions with minor adjustments so that scale formations won’t build up on the walls, and filtering system of the pool.
You can also run your pool at lower levels with the same precautions, making minor adjustments so that the pool’s structure is not damaged or pitted. The controls you use will be Alkalinity and pH
Hardness is a measure of Calcium and Manganese but in pool water, we are only interested in Calcium.
Hard Water with high calcium content gets cloudy unless the pH and or Alkalinity are low enough to compensate. The excess calcium carbonate will precipitate as crusty, grayish-white scale or staining on surfaces, piping, and equipment. It’s unsightly, can cause abrasions on swimmers, and makes a good anchor for microorganisms.
When it builds up in piping, the pressure will increase and clog up filters and their media. If the pool water is heated, Calcium can be a particular problem. With higher temperatures, less Calcium can stay dissolved, and cakes upon heating coils and other equipment. This causes more energy to heat the water and eventually make the pool heater fail. Other noticeable issues will be:
- Cloudy Water
- Rough Surfaces
- Clogged Filters
- Reduced Circulation through Piping
- Higher Pressure readings on the system
Soft Water with low Calcium content seeks more from contact with surfaces that contain it. In a pool, the surfaces that contain Calcium are plaster, grout, and concrete decking. Low Calcium in pool water is corrosive to the pool if the pH and the Alkalinity are not Balanced. Again it can be Controlled by Alkalinity & pH. Other Noticeable Issues will be:
- Pitting of concrete surfaces
- Etching of Plaster
- Dissolves Grout
- Pitting of Concrete Decking
Testing Your Pool Water For Calcium Hardness
Not all drinking water is considered hard. If you use a well you know pretty much for sure it is. That’s why it’s important to know how to test your Pool properly. Take a little time and discover how and why your pool water contains Calcium as Hardness and how much Hardness from Calcium is too much or too little. You do this by Testing.
The best reliable Test Kits for Swimming Pools will use titration methods. If you want reliable results then pay a few dollars more and throw away the Test Strips. Test Strips only measure Total Hardness and in color blocks with a wide range. You need to use test results of Hardness from Calcium that will result in smaller increments. This will give you more control as an Operator of your Pool.
The Titration method with fresh reagents will break the results down in as small as 10 ppm. This is more accurate and specific to what you need. To make your pool water the best and softest you need a reliable Test Kit. Why because without it none of this information will work. Take a Look at this one I personally recommend that’s available at Amazon called LaMotte ColorQ Pro 11 TesTabs Digital Pool & Spa Chemical Water Testing Kit
A Calcium Hardness Test Looks like this:
1. Fill the test cell with the sample water an 2. add the buffer and the indicator reagent and swirl to mix. The sample will turn red if Calcium Hardness is present 3. next add a Calcium Hardness reagent and count the drops, swirling the cell after each drop you add until it turns blue. 4. After the sample turns blue add one more drop of titrant to make sure that the sample doesn’t turn back or change back to red-then-subtract that drop from the count.
Sometimes when measuring Calcium you may get a fading endpoint that will result in a purple color. This interference is from metal ions in the pool water. To deal with this rinse out and re-take your sample and this time add five or six drops of Calcium Hardness Reagent to the sample before adding the buffer and indicator.
Langelier Saturation Index Formula
In swimming pool Calcium is dissolved in the water If it is too much it will fall out of saturation and can cloud the pool and create scaling and staining in the system. If there is not enough Calcium, the water is not balanced and you will develop problems that destroy the structure of your pool.
So to keep your pool water balanced and chemically controlled. Learn how to Use The Langelier Saturation Index or LSI that will give you (the Pool Operator) a ballpark way of seeing this Balance that dictates what can happen in your Pool if Calcium becomes too high or too low. The LSI Index will rely on:
This Ballpark measurement and is meant to be a generalization of preventing low Calcium content that can cause a negative corrosive action like pitching of the walls or a high Calcium content that can cause scale and cloudiness in the pool.
Saltwater pool operators include Total Dissolved Solids which includes the salt content of the water. Others use Cyanuric Acid in the equation that can also have a minimal effect but I feel complicates it so I left them out.
Your objective is to operate your swimming Pool the very best that it can be and save money while you do it. This Index is not an exact science so it doesn’t need to be further complicated. You want the Index to be close to 0. between < .03 and >.03. This is where your pool water is balanced between Hard and Soft water.
Anything less than 0 is considered corrosive and Soft even though you would tend to think that Soft water wouldn’t be corrossive, it acts this way.
Anything more than 0 is considered Hard which can cause minor problems if its not controld like scaling and cloudieness. So the operator is aiming for 0. It doesnt have to be 0 but you want that desirable range to keep it balanced. It won’t change fast so its not necessary to run the test on a schedule like Alkalinity.
I was a Lab Tech in a Certified State Licensed Lab that monitored effluent water after it was treated and let go into recieving streams. I learned that chemical formulas were based upon years of Standards and Practices that originated from years of testing by some pretty smart dudes.
As an Operator in water treatment just like a swimming pool operator, you can can keep it simple by knowing what, why and how and trust the rest to the dudes that write the Standard & Practices Manuals for the Industry. The LSI index works like this:
If the Total Alkalinity is 50 ppm; & the PH is 7.0; Calcium Hardness is at 200 ppm & the temperture of the water is 76 degrees then the Saturation Index or the LSI is equal to -0.9 which will indicate the pool water is somewhat corrossive and Soft. Here are some methods to raise and lower Calcium levels.
Add Calcium Chloride-To raise Calcium Levels – As calcium chloride readily dissolves in water, it is commonly used on winter roads as a de-icer. It is normally solid at room temperature, but if left in the open air, can gain moisture to the point it becomes partially a liquid. It should be easily calculated on how much to use but don’t pre-mix it. Broadcast the powder around the parimeter of the pool and watch out for it blowing in your eyes.
Calcium Chloride comes in 77% or 100% so the formula to raise the Hardness in your Pool water:
2 oz. of 77 % Calcium Chloride will raise a 10,000 gallon pool 1 ppm or mg/l
1.5 oz. of 100% Calcium Chloride will raise the hardness 1 ppm or mg/l in a 10,000 gallon pool.
The Solution is Dilution-To lower Calcium Levels
If your home is hooked to a well and in most cases is equipped with a water softening system, limestone filters that exchange calcium ions for sodium ions. But most outside hose bib spigots aren’t connected to the water softener system.
You can connect a hose to fill the pool with filtered, softened water by connecting a hose after the sediment tank or in the kitchen or laundry room. This way you can add soften water to your pool.
You may not want to fill continuously, but most whole House systems can handle 8-12 hrs per/day of filling the pool. Better yet fill some of the pool with the softened water. That should be enough to the dilute Calcium in the pool water.
Go Green with Water Filtration-To lower Calcium Levels
For most people around the country emptying your pool is not a viable solution economically or environmentally. There are companies that can come out and filter the water in your pool with RO filters(Reverse Osmosis) built into trailers and run the water from your pool through the trailer taking out Calcium or Magnesium that can change the Hardness level of the water.
Calcium Hardness is a big problem for fill water around the States but especially in the Southwest where because of water restrictions emptying your pool is not an option. Evaporation is a huge problem which could increase the mineral contents in concentration. So dilution is not as acceptable as where I am on the East Coast. Using Reverse Osmosis is a great idea for lowering Hardness from Calcium, Cyanuric Acid and Dissolved Solids that can all add to it.
The Trailer is set up in the driveway of the owners pool and a suction and return hose is assembled to the fitration unit and the pool. The filter is self contained and uses no electricity. You can even swim in the pool while its being filtered.
The effluent water after being filtered is cleaner than bottled water. The process can take about 8 hours for a 40,000 gallon pool. Price on the West coast is around $650.00 for a 25,000 gal. pool. You won’t ever need to empty and refill your pool again.
Muriatic Acid Treatment-To Lower Levels & Add A Silky Smoothness to the H2O
I used this in my pool in the “Dog Days Of Summer” when the pool water is the warmest:
High pH & Warm water temperatures will allow dissolving calcium carbonate to come out of solution and show itself so that you can see it cloud the pool. When you buy this product make sure you buy the Contractor’s Strength Muriatic Acid and use the calculation for your pool size and the strength of the Muriatic Acid on the label.
Remember Alkalinity and pH will change slow-so …………………….take your time. the Muriatic acid will scrub the pool water clean and add a silky smooth soft appearance that has consistency and beauty to it.
Test Calcium Hardness with the Titration Method explained above & use the LSI for formulating a result.
Before you start to add a little fill water:
- Add pH Plus and raise PH levels to 9 or10.
- Circulate the pool filter on the Multi-port handle adjustment so the pool water mixes well.
- Add a Flocculant at night- broadcast the precipitate around the pool-premixing is a good way of doing this in a 5-gallon bucket with some pool water and the chemical.
- Run the filter on Recirculate all night-8 hours or so.
- Shut the filter down and let the pool sit for 8 hours or so and Vacumn to Waste.
- Re-Adjust Alkalinity back to a normal range of 80 to 120 ppm
- Use Muriatic Acid to bring the PH back down to normal range which is 7.2-7.6
- Re-test Calcium Hardness it will be lower.
- If the water is still a little cloudy use a polisher or clarifier again and vacuum.
Operating a Pool With Hard or Soft Water-Deal With It!
I am totally on board with the fact that you should be able to control Hardness with your PH & Alkalinity. Lowering or draining your pool to dilute the hardness is not the way to go unless there is a crazy amount in the pool.
The water you used to fill the pool will still have the same levels of Calcium that will most likely start at lower levels at the beginning of the summer and end up higher in September.
So if your fill water is Borderline High in Calcium content deal with it. If you can’t, then make an adjustment with the fill water like the ones that I mentioned above in the article then use Muriatic Acid to lower pH and Alkalinity using them as controls for stopping scaling and stains in your pool.
If your pool water needs more Calcium in its diet switch over from pool tablets to Calcium Hypochlorite. Use the Granular chlorine as mentioned in earlier articles on MyWaterEarth&Sky called Granular Chlorine Vs Tablets? for bumping Chlorine levels and adding other different type controls for operating your pool and saving money while you do it.
Either way, money won’t be an issue. Muriatic Acid is very cheap and you can buy it almost anywhere. It also has numerous applications that can be used around the pool.
Use safety procedures whenever you use Muriatic Acid. Wear chemical-resistant gloves and safety goggles.
Never mix water into Acid instead Always mix Acid into the water. Raising Alkalinity and pH with Muriatic Acid is a slow process. Don’t overdo it. Test then add the Muriatic Acid then test again until it slowly returns to normal.
Muriatic Acid will dissolve and rids Calcium deposits and stains through the whole pool and filter. It will create a soft silky feel and appearance to the pool water that is very noticeable to people swimming in it.
The Pool Industry today seems to invent problems in order to confuse and complicate the maintenance of operating one. The solution for everything doesn’t come in a tub or bottle. Like the new Phosphorus dilemma that was invented last year along with a new Phosphorus solution that was available at the Pool Supply store at the same time. Be The Master of Your Pool!
Buy a reliable Test Kit, yes, educate yourselves on the basics, yes and you’ll have a beautiful pool all summer long and save money too!
How do I make my pool water crystal clear?
Administer Shock and Algaecide Weekly. Even if you maintain proper chlorine and pH levels in your pool, the water may need a little boost to keep it clear and sparkling. Once a week, you should shock or super-chlorinate your pool to kill any lingering bacteria or algae that may be growing.
Will baking soda clear up my cloudy pool?
Baking soda or Sodium bicarbonate raises the total alkalinity of the water. This affects the waters total balance naturally with The calcium hardness, pH and temperature. is a base and will increase the level of pH will have some alkalinity to the water in the pool.
How long does pool clarifier work?
If pool clarity problems began with an algae bloom, be sure to kill algae before Clarifier treatment. This requires 10-30 ppm of shock chlorine, with a suitably low pH of around 7.2. Operate the filter 24 hours per day by Recirculating during treatment to mix the pool then vacuum.
Reference: Hard Water Chemistry and Reducing Calcium in Pool Water
Jim has over 30 years in Water/Wastewater & Water Filtration Business. He has written over 200 articles on the Worldwide Water Situation.