Concrete products cure over their life time, getting harder and harder, but in the first 28 days they reach between 95% and 98% of their maximum hardness. This makes the first 28 days of your new pool finish the most vital. It is the job of a proper startup to make sure your pool plaster cures properly and is as strong and dense as possible.
Your pool chemistry is based on equalibrium- the new plaster and the pool water want to reach equalibrium chemically. The new curing plaster has a very high pH and the pool water does not, so high pH calcium will want to leach or migrate out of the new plaster and into the pool water to raise the pH of the water. Also the pool water with a lower pH wants to attack the new plaster (etch) to lower the plaster's pH. This process weakens and makes pourous the new pool finish.
Some in our industry accept this weakening as a norm and have named the calcium that migrates or gets etched out of the pool plaster "Plaster Dust." What it is is Calcium Hydroxide, and it represents a weakend new pool finish.
Bay Are Pool Service does not accept this as the norm nor do we consider it to be the proper way to Start Up a pool.
Calcium Hydroxide "plaster dust" can only exist at pH 8.4 and above. At pH 8.3 and below it will remain inside the plaster and form Calcium Carbonate during the pool plaster curing process adding more stregth to the final product.
So we should dump in a bunch of Acid to keep the pH low right? WRONG!
Again your new pool plaster is curing, it's realatively soft, it needs to be babied, acidic water will further attack the finish and create more etching porousity. Yes it is the flip side of leaching porosity but it is still bad. End result of too aggressive water is a weakend and pourous plaster finish. We can do better! Ask any potential Plastering Contractor how they start up pools and be wary of any who say they dump acid in the pool then they are done- leaving you alone after only a day or two.
The Bi Carb Start Up
Bay Area Pool Service uses the BI Carb Start Up method. Sodium Bi Carbonate is added to the pool water as soon as possible to increase the akalinity and peg the pH at 8.3, Bi Carb's pH. Bicarb acts as an anchor for the pH not allowing it to fluctuate during the curing process and by holding pH high but just below 8.4 calcium hydroxide can't form. This higher pH water chemistry slows the leaching process to a crawl since we are close to equilibrium already! The curing plaster and the water are both on the basic side so there is less chemical desire to leach.
Any calcium hydroxide that does leach hits the pH 8.3 water and converts to Calcium Carbonate. The leaching process quickly stops. All remaining calcium in the plaster forms calcium carbonate a strong part of the plaster finish. The end result is a stronger, less porous finish that will resist stains better and last longer than a similar finish started up with an aggressive startup, or a start up that allows plaster dust to form.
So why doesn't everyone do it? This is a long, slow and labourious process. We figure between 11-15 visits to each pool during the 28 day curing process. Most pool plastering companies are already at the lowest common denominator of competeing on price and are not prepared to tell you these things or do the work needed to make sure your new investment in a pool finish is protected. Remember to find out what start up procedure they provide and what your role will be in that process.
We believe in this method
The Bi Carb Start Up is included in all our full priced pool finish jobs and is an option on all our sale priced jobs. We also offer it to our clients who have had their pools refinished by another contractor at a price of $475.00.
When we do the Start Up we take care of all the trips, so you don't have to. That's the way we think it should be done. If your contractor is telling you they put chemicals in the first day and "then the pool is yours," give us a call before you start for a professional alternative.