The following information 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 most importantly, a high alkalinity level. The best water for new plaster should have a positive Langelier Saturation Index (LSI). Even if the tap water is LSI balanced, it is aggressive to new plaster and will remove plaster 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 dirty or stained (gray mottling is a different issue), 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.
The Bicarb start-up prevents the pH from rising above 8.4 which generally happens, and is a common battle with most new plaster pools when filled with average tap water. The Bicarb start-up allows for fewer visits during the first month 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 do 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.
The Bicarb start-up program adds sufficient alkalinity to the tap water before filling, so that it is not aggressive to new plaster. A minimum of 200 ppm of alkalinity is required, but a higher amount may be needed if the calcium content of the tap water is low.
The above 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!
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:
Comments
Sounds like it's a traditional plaster finish with a color added to it-gray perhaps? If so, the swirls you see are from the trowel marks. Your plaster crew may have added calcium to speed up the curing which will give you the swirls and yes mottling too.
As been mentioned in this thread, the start up procedure is extremely important to hopefully prevent this discoloration with any material.
I do however state in my contracts that ANY plaster finish can have some color differences as their makeup is natural and man made.Try to upsell exposed finishes over traditional plaster material with dyes or colors added. Exposed finishes are a little lore consistent in their colors as they are made in batches at the manufacturing plants. Others are mixed on site and sometimes do not offer consistency mix to mix
Jared, severe plaster "mottling" is a gray discoloration (in blotchy or streaking patterns) of the white plaster material itself. It is not a stain or deposit on top of the plaster surface. Read my five past blog posts on "Gray Mottling Plaster Discoloration"
New plaster pools (the first three weeks) that have a lot of "plaster dust" means that plaster material is being removed from the plaster surface. The best program is to prevent plaster dust from forming, and not to have to deal with it at all.
I do not know what the "swirl stain" might be without knowing the color of it, and a picture would be very helpful.
What is the difference between plaster dust and molting ? How do you remove plaster dust ? I re-plastered a pool in May 2011 and about two months later started to noticed a swirl or vein looking stain.
Thanks so much for your response Kim! It is a big help, and I will keep this in mind for the future.
Patrick,
Because the tap water is LSI aggessive, a Bicarb startup would have been especially beneficial. Compounding the tap water before it enters the pool would have kept the plaster surface from being etched, and therefore, more dense. This would reduce the blotchy and/or lightening in color appearance. In my opinion, the plaster surface is now porous and slightly etched, so that is why the splotchiness in color.
Once a pool has aged and cured for a while, a Bicarb startup will not help as much for a refilling project. But it would help some if some bicarb was added during the filling process when the tap water is soft, such as yours. And of course, get the water balanced as soon as possible once refilled.
I found this post to be most interesting. I have a pool/spa that was refinished with DiamondBrite about 2 years ago. They were immediately filled with tap water. The typical readings for this water source is pH 7.3, TA 30, and CH 70. The surface has somewhat splotchy in color. There are rough areas and smooth areas also. They are typically drained for maintenance periods once or twice a year for 30+ days. Upon refilling with cold water (50 deg.) they have a constantly rising pH which is countered with dry acid. Typically, the CA test has a vague endpoint. When the heat is turned on several days or weeks later, everything seems to return to normal and the chemistry is stable.
Would a bicarb startup have mitigated/prevented the above problems? Would a bicarb startup help the next time they are drained for a maintenance period?
peaKim,
Yes very interesting,in my plaster which is 100% Quartz and to obtain the background color I add Colored Quartz I do not use any Oxides whatsoever to our White Portland Cement which is added at the site (not premixed
The size of the Colored Quartz provides a good color the finer the better to the Quartz the only additional additive we add is a Polymer to provide ease to work and as a bonding agent.
Because the Quartz is unaffected by Acid the only thing that ca be effected by poor water balance is the cement.
It is my belief that some of the Plasters being used or mixed are just the same old Marble with some Quartz added along with oxides them baged and given a fancy name.
To prove my point I get these products and put them into some acid, looks like creaming soda and it vanishes.
As another matter of interest Quartz used as a Filter Media is just the best from all the times I have used it.
On a recent pool that I designed and built in Shanghai the water was slightly yellow with rust in the water supply which with a blue glass tiled background gave me an instant green pool but after 16 hours of filtration the water was Crystal Clear and apon back washing out came what looked like black coffee.
We can all learn something every day.
Kim email me if you wish kiwipool@vodafone.net.nz
Norman, that is a very interesting question. According to the Portland Cement Association, adding sodium bicarbonate can either speed up or slow down the hydration of cement. They also suggest that the strength of such a high concentration might compromised the strength. So they don't provide a definitive result or answer.
By my calculations, it would require about 250 lbs. of bicarb (per average pool) to react with all of the calcium hydroxide formed in the cement and convert it into calcium carbonate.
It is known that certain pozzolans can be added to cement which will convert calcium hydroxide into the C-S-H gel (calcium silicate hydrate) which also improves strength. However, it is my understanding the this reaction can sometimes cause a discoloration issue in pool plaster.
Maybe an experiment can be conducted sometime to learn about this intriguing possibility.
Question Kim.
What is wrong with adding some Bicarb to the Plaster mixture. Any thoughts on that because it is only going to have an effect on the cement.
Kiwi www.poolquartz.co.nz
Thanks again Kim.
Most of my customer's have their own personal wells or the "city" water comes from artesian wells. It's generally high in minerals thus a higher pH value. Hard water. Some residents have water softeners and one must be careful not introduce softened water into fresh fills. Generally it's relegated to household water and not the typical hose spigot.
There are neighboring towns that have water service from a water company that gets their supply from a resevoir that essentially is "treated" before sent out to households.
I usually test that water before I fill as it actually varies from town to town even though it comes from the same water company. Sometimes a high iron content.
My customers with well water, I already know what to expect and treat accordingly.
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