Why the BiCarb Pool Start-up is Best
December 5, 2011
Reprinted with permission from Kim Skinner of On Balance:
The following information on chemical start-ups is applicable to all newly plastered swimming pools, including quartz and pebble aggregate finishes.
The first step for a superior start-up is to wait at least six hours before turning on the water to fill the pool. This was common practice in the old days. If filled too early, some plaster material dissolves from the surface, mainly in the deep end, leaving it porous and susceptible to further erosion and staining.
The second step is to fill the pool with water that has sufficient calcium, or more importantly, a high alkalinity (TA) level. The best water for new plaster should have a positive Langelier Saturation Index (LSI). Even if the tap water is balanced, it is aggressive to new fresh plaster and will remove material from the surface and negatively affect the long-term durability due to increased porosity of the surface.
Those first two steps are, for the most part, what the Bicarb Start-up program is all about. It is not any more complicated than that. Other start-up procedures, such as the Traditional start-up, do not deal with these two important steps, which may allow filling the pool too soon, and with aggressive tap water. Only afterwards when the pool is full, when the damage has already occurred, is the water treated and balanced. Far more damage can occur to a new plaster surface during filling than over the following two weeks, even if not balanced.
The following is the science on how and why the Bicarb start-up method protects the plaster.
When water and pool plaster is mixed together before applying, most of the hardening plaster is comprised of calcium silicates and aluminates, and about 15 to 20 percent is calcium hydroxide. Calcium silicates and aluminates are the hardest components, but calcium hydroxide is softer, slightly soluble, and a weaker component of pool plaster. In fact, calcium hydroxide can be dissolved by typical balanced pool water. The LSI is applicable to calcium carbonate, not calcium hydroxide.
This is exactly why tap water that does not have a positive LSI is not suited for new fresh pool plaster. As much as 30 pounds of calcium hydroxide and other pool plaster material can be dissolved from the plaster surface of a 20,000 gallon pool, depending on the severity of the plastering and aggressive tap water conditions. The calcium hardness of the pool water can sometimes increase 100 to 200 ppm.
It is the dissolved calcium hydroxide that becomes “plaster dust” (in the pool) as much of it is transformed into insoluble calcium carbonate by the pool water. The amount of plaster dust formed can indicate how much material has been lost from the pool plaster surface. The more material that is lost, the more porous and rougher the plaster surface is (as seen under magnification), the less durable it is, and the more likely dirt, iron, and copper will stick to the surface as time passes. And months later, when the plaster surface looks aged, and dull, and discolored, no one will suspect it was due to the improper or ineffective start-up program the pool received. Whoever is maintaining the pool will be blamed for the negative change in appearance.
A Bicarb start-up prevents the loss of calcium hydroxide from the plaster, which preserves a dense (non-porous) surface, and no plaster dust forms. Instead, it converts calcium hydroxide WITHIN the plaster surface into calcium carbonate, creating a harder, denser, smoother, and more durable surface. And there is no increase of calcium hardness in the pool water.
The Bicarb start-up program helps prevent the pH from rising above 8.4, which generally happens in new plaster pools, and is a common battle to control the pH when filled with average tap water. It does this by adding sufficient alkalinity (TA) to the tap water before filling, so that it is not aggressive to new plaster. Low alkalinity water creates two problems; it can dissolve calcium hydroxide from the plaster, then the high pH (12.4) calcium hydroxide dominates the pH of the pool water causing it to rise very quickly and very high (sometimes as high as 10.5). A minimum of 200 ppm of TA is required for proper pH control and buffering, and a higher TA may be needed if the calcium content of the tap water is low.
The above pictured pool/spa combo, featuring black plaster, was set up as a Bicarb start-up. You can see the barrel and hoses in the background. When we came back, the pool was crystal clear, but the spa looked like it was full of milk (especially once we brushed it!). The homeowner had come home and decided to fill the spa using non-bicarbonate tap water. What a difference!
The Bicarb start-up allows for fewer visits to control the pH. There is a reduced need for intensive brushing. Because the plaster surface is smoother and more durable, it stands up better to future acid washes and dirt and mineral stains are easier to remove. Dark colored plaster stays darker and does not become blotchy or lighter in color. Long-term esthetics is definitely improved. Acid start-ups can be one reason for colored plaster and quartz finishes becoming blotchy and lighter in color.
Of course, many will assume that scale will develop because of the high alkalinity level (having a positive LSI). But if the Bicarb program is done correctly, scale doesn’t form. For over 10 years, many pool plasterers and service techs report having great success with the Bicarb start-up method. The entire pool plastering industry should adopt this start-up program to ensure quality and durable pool plaster.
For the specifics steps on the Bicarb start-up go to: https://www.poolhelp.com/handouts/oB_Bicarb%20Startup%20Method%20Handout.pdf
On Balance, December 2011
Mike the Poolman
Pool Service & Repair in Folsom, CA since 1995