Aquatic Technology Pool & Spa, "Creating Water as Art."™

Aquatic Technology Pool & Spa, "Creating Water as Art."™
Pools as an art form - the way it should be!

Wednesday, June 24, 2009

Managing your water chemistry... maintaining an even keel.

Maintaining the water chemistry in your vanishing edge pool, infinity edge pool, negative edge pool, perimeter overflow pool, flooded deck pool, or perimeter overflow pool, is all about consistent & even monitoring, automated chemical control, and dispensing of chemicals.


There are a number of factors that contribute to the "balance of the water." The most important are the pH and the alkalinity. The alkalinity is the ability of the water to buffer the pH (or buffer chemicals that may effect the pH). The alkalinity is like an auto-pilot or cruise-control for the pH.

If the alkalinity is out of the acceptable range, then any small factor will cause a wild swing in the pH. This is called "pH bounce." Because of this, the alkalinity is the first thing that should be brought into line when balancing the water.

An ideal range for the alkalinity is 100-120 ppm (though 80 - 140 ppm is acceptable).

pH 7.4-7.6

The pH of the water, determines if it is acidic or basic. Either extreme can have disastrous effects on the pool finish, equipment, or plumbing. When the pH is out of range, bathers may complain of eye discomfort or other ailments.

An acidic pH will cause the water to become aggressive. It will etch the plaster and cement finishes around the pool. Worse yet, it will dissolve the metallic components of the pool. The most expensive metallic component is the copper heat exchanger within the pool heater.

The ideal range for the pH is 7.4 - 7.6 (though 7.2 - 7.8 is acceptable).


After the alkalinity & pH are brought into range, the next adjustment is the sanitizer. Chlorine is the most common and least expensive of the available sanitizers. The acceptable range is 1.5 - 3 ppm, though 4 - 5 ppm is absolutely fine. A commercial spa should be maintained at much higher levels - 5 - 6 ppm.

A residential pool should be maintained at 3.0 ppm. The higher levels ( 4 - 5 ppm) should be established, prior to a large party or heat spell. Try not to allow the levels to drop below 3 ppm, as this will prevent the need to shock or take other corrective action after the party.

Total Dissolved Solids

Like it says, total dissolved solids (TDS), is the sum of all of the "junk" in the water. It includes dissolved minerals, salts, etc. We refer to this as the "junk in the trunk." When the TDS exceeds approximately 1500 - 1800 ppm above the initial starting point, then it is time to "dump some water." If the make-up water is "soft water," the dilution process will occur much faster (though the salt in the water will add some to the TDS).

Calcium Levels

Calcium is required to prevent the water from becoming aggressive. If there is not a sufficient amount in the water, it will seek an equilibrium and literally draw calcium from the plaster, tile grout, or other cementitious material.

A minimum of 200 ppm is required to prevent aggressive water. However, should the calcium level rise to 400 ppm or above, you can get scaling. Any drastic change in pH (like when adding liquid chlorine), and you can precipitate the calcium out of solution. It will attach to the plaster & cause a rough bumpy surface.

If the water begins to draw the calcium out of the plaster, the plaster surface will begin to feel like sandpaper.

Tile Scaling & Haze Build-up

A build-up of a white film or haze on the tile has nothing to do with the service company not scrubbing the tile... it is merely from the evaporation of water in the pool. As the water evaporates, calcium is left on the tile. Over time, it begins to cause what appears to be a haze.

It is actually calcium, like what is left on your drinking glasses in the dishwasher. To remove it is an additional cost, just like having your car detailed & waxed. Most pool service companies can remove the hazy build-up with specialty chemicals (high strength acids). These acids work by dissolve calcium, but they are "stupid" chemicals because they do not know the difference between the bad calcium (on the surface of the tile) and the good calcium (in the grout between the tiles). The use of these acids more than likely will damage the tile's grout.

An alternative is to hire a firm that utilizes "bead blasting." It is like sandblasting, but fine glass beads are used instead of aggressive sand. Various sizes of glass beads are available, down to very fine like talcum powder.

To prevent (or greatly reduce) the build-up of scale on the tile, a water softener on the fill line can remove all of the calcium from the water. You will have to monitor the calcium levels to maintain the 200 ppm minimum that is required.

But, it is much easier to add calcium, than to remove it. Though a water softener can cost $1000, living with the unsightly build up & the cost of removing it will quickly cost more than that (ROI).

Paolo Benedetti - Aquatic Artist
"Creating water as art."™
Aquatic Technology Pool & Spa