Those of us in “hard water” areas of the U.S. know what’s it’s like to have gritty scale from water hardness at the bottom of a swimming pool. So the idea of filling swimming pools and hot tubs with soft water sounds fantastic.
Although there are pool owners who have successfully filled and maintained their pools with softened water, pool owners should understand that filling a pool with soft water is not simple. It involves a very delicate balance. In fact, maintaining the right levels of hardness AND softness is essential for a healthy pool.
The Fallout of Hard Water in Swimming Pools
Water described as “hard” usually has a high mineral content—generally calcium and magnesium. As more and more of these minerals dissolve in water, the mineral content levels increase, making the water harder. Excessively hard water can leave a coating of white, gray, or brownish deposits on pool walls and floor.
When pool water is too hard, a chelating agent can be added to render the calcium inactive and make the water “softer”. The agent actually bonds with the calcium ion, keeping it in solution and preventing it from plating out as scale (calcium carbonate).
“[Scale] is a combination of carbonate ions and calcium ions. “Hard” water can have high levels of calcium and magnesium. If these levels are too high, the water becomes saturated and will throw off excess particles (scale) out of solution which then seek to deposit themselves on almost any surface inside the pool. They can be attracted to ladders, lights and deposit themselves as very small crystalline clumps – all over the pool surfaces. Calcium Carbonate scale shows up as a “white-ish,” crystallized rough nodule.” (PoolCenter.com)
Yes, hard water can cause grief—so if you have a home water softener (and especially convenient if you’ve had a soft water exterior hose bib added) soft may seem like the obvious solutions. But hold on…
Soft Water Must be—Harder!
In the home, there are many benefits of soft water—from spot-free dishes to brighter laundry. But in a pool, some calcium hardness is a necessity.
The trouble in filling a swimming pool with softened water is that “soft water” may seek to balance itself by leeching calcium directly from pool walls—causing the pool’s plaster or tile grout to dissolve, corrode and eventually crumble. And anyone who’s had a pool replastered knows that it’s a huge expense.
“If the Calcium Hardness levels are too low, the water is under-saturated…[and] will become aggressive as it attempts to obtain the calcium it needs. Such “soft-water” will actually corrode surfaces inside the pool which contain calcium (like pool plaster) and other minerals to maintain its hardness demand.”
In addition, everything metal in the pool area such as heaters and railings can also gradually corrode from the soft water. This problem can be exacerbated if a pool owner allows the pool’s pH level to plummet and stay low for an extended period of time.
So while swimming in soft water may feel great, the soft water can greatly damage the pool.
Those who have successfully maintained pools with soft water generally increase their water hardness by adding calcium chloride or calcium chloride dehydrate found at pool supply store. Basically, all that wonderful soft water is now harder.
So, what is the right solution?
Regular Water Testing is the Key
Either way—whether you’re filling your pool with hard water or soft water—testing is essential.
Keeping water in balance is no easy task. Regular tests for pH, alkalinity and calcium hardness are essential. (The test for calcium hardness is not only the indicator of how “hard” your water is, but also how “soft” the water is).
Many pool supply stores offer a free water sample test and analysis, and home test kits can also be purchased to evaluate these properties. Check with a local pool expert to determine what level of softness/hardness you should have in your pool. By maintaining the correct water balance, the life of the pool equipment and pool itself can be extended.
Keep in Mind that filling a pool from a water softener can be time consuming. Most water softeners can only fill a pool with a certain number of gallons before needing to regenerate. Check with your local water treatment expert or consult your softener manual to determine how long you can fill your pool before stopping to allow time for the softener to backwash and regenerate.