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SU Series #1 - The "Bicarb Start-up"

Many of you have heard that onBalance uses an alternative chemical start-up method for new plaster pools, and have asked what it is, how it works, and why it is better than both the traditional method, and especially the acid start method.

In a nutshell, the “Bicarb Start-up” is a method which eliminates the formation of “plaster dust” and which results in denser, smoother, more durable plaster than other techniques.

How does it work? As you may know, when a new plaster pool is filled with water, it normal for a percentage of cement paste at the surface to dissolve into the water, and form a solid calcium carbonate precipitate – which we in the pool industry call plaster dust. This plaster dust is then brushed and filtered and brushed and filtered and so on, until it is gone.

When using the bicarb start-up method, the fill water is saturated with baking soda (sodium bicarbonate). This “fixes” or converts “in place” most of the calcium hydroxide in the surface by converting it to the more durable calcium carbonate. As a result, less calcium is released into the water, and the surface retains more of its original constituents resulting in a denser finish.

Since this is the subject we get the most questions about when we teach classes, in the next few emails we would like to tell you how this works.

Note – we are primarily interested in the chemical manipulation of the water, and its effects on the water balance and the plaster surface. Obviously, start-ups can also include “mechanical” issues (starting up pumps, filters, heaters, installing automatic cleaners, etc.), “maintenance” issues (brushing and filtering to remove the “plaster dust”), training the pool owner, etc. – but we are confining this discussion to the chemistry.

SU Series #2 – A pH Value & Calcium Solubility

Now, to understand start-up chemistry, there is a pH value to keep in mind – pH 8.3. Above 8.3, calcium carbonate, or scale may form, and the higher the pH rises above 8.3, the more carbonate scale is formed. So we call high pH levels (over 8.3) “scaling” pH levels.

Below pH 8.3, calcium tends to stay in a soluble “bicarbonate” form, constituting the calcium hardness in the water.

So in order to “force” all of the calcium in the water to remain in its soluble form, there is a simple method – keep the pH below 8.3!

The form of calcium that “bleeds off” into the water (calcium hydroxide) from the plaster surface has such a high pH (in the 10+ range) that under normal filling procedures (i.e., when the water is not pre-treated), the pH of the pool water jumps immediately and almost always exceeds 8.3 – which begins to convert the calcium in the water into scale. This is the “plaster dust” that we see for the first 3 weeks.

There are several methods to keep the pH of the water lower – but some are aggressive to new plaster (such as the acid start), and one is not. The one that isn’t aggressive is the bicarb method.

What is sodium bicarbonate? Baking soda! It is so safe, you could eat it! (In moderation, of course…) What is useful about baking soda? It has a pH of… 8.3! So water that has lots of baking soda in it (saturated) has a pH of 8.3.

Saturating fill water with baking soda not only helps keep the pH at 8.3 or below, but it also provides enough bicarbonate to impede and reduce the dissolution of calcium hydroxide from the plaster surface. It does this by reacting with and converting calcium hydroxide on the plaster surface into a protective layer of durable calcium carbonate, thereby creating a more dense and harder surface.

SU Series #3 – The Bicarb Start-up Method Sequence

We have prepared a “handout” for our classes that describes both the sequence of events for a bicarb start and the methods we use of accomplishing those steps. You can review that document at our website – www.poolhelp.com/oB-BicarbStartMethod.pdf

The main steps are:

1 – Pre-testing the Water

2 – Calculating the Chemical Dose

3 – Setting up the Delivery System

4 – pH Adjustment

5 – Determining Fill Delay, Turning On the Water

6 – Making Adjustments

7 – Monitoring the Progress

8 – Final Balancing

Feel free to print out a copy and give the method a whirl. If you need clarifications or questions answered, be sure to send us an email.

SU Series #4 – How the Bicarb Method Compares
The primary, immediate difference noticed when doing a bicarb start instead of a traditional start is that there is virtually no plaster dust. Over the long term, there is also better, more durable and smoother plaster.

While the acid start will also eliminate plaster dust, help colored plaster pools to retain their color, and dissolve white deposit; it also has a serious drawback to its method.

Acid start-ups, where a minimum of four gallons of acid is added soon after the pool is filled with water, will usually dissolve all plaster dust formed, but unfortunately also dissolves and etches the entire plaster surface at the same time. This process leaves the surface rougher (as seen under magnification), which in turn makes it less durable, easier to stain, and harder to clean in the long run.

Furthermore, once the acid start program is over, it can be tricky to raise the pH and alkalinity and balance the water without creating scale. In addition, it is often the case that the person who performs the acid start realizes the short-term benefit (a clear non-scaled pool), but the person who provides the subsequent maintenance suffers the long-term deficit (rougher plaster and worse staining).

The downside to the bicarb start is that it must be prepared ahead of time and requires the setting of a 55 gallon plastic drum at poolside during the filling. Quite a lot of benefit for relatively little fuss.

SU Series #5 - The Results

We know of several pool plasterers who had difficulties creating and maintaining consistent color on colored plaster, quartz aggregate pools, and with hydrazzo pools. These plasterers were using the acid start-up method trying to stop white scale from developing on these special pools.

These plastering companies began bicarb starting all of their colored cement pools – the color was darker and more consistent, and the white film deposits no longer formed! For them, the set-up and take-down of the barrel and hoses was a far better investment than adding acid/brushing/filtering and then more of the acid/rebalance routine if the first round wasn’t satisfactory.

In addition, over time, these bicarb started pools retain their superior finish much longer due to the smoothness and the additional density of the protective, carbonated surface.

Keep in mind, however, that pools which are filled too soon and/or have a high water-to-cement ratio make more plaster dust, increase the calcium content of the water, and result in less durable plaster (with higher porosity) than plaster with a low water-to-cement ratio and/or that is allowed to harden more before filling – even when using a superior chemical start-up method.