Plaster Installation and Maintenance

Plaster Installation

In most cases the Pool Builder or "contractor" who you are hiring does not have the plaster crew working for him. He subcontracts the plaster work to a specialty contractor. So all your talk to your "contractor" about the quality work you want done is rarely passed to the actual crew who will do the work. There is no substitute for being on site when the plastering is done and watching closely that they follow the best practices described in our articles. Plastering is a custom manual process where decisions made on the job site affect the quality fo the work you get.

Get educated and get involved in watching over your project. Trusting a contractor and just writing checks is rolling the dice on getting a quality plaster job.

Ten Guidelines for Quality Pool Plaster There are proper steps to follow for the making of durable pool plaster. There are also improper practices that can lead to early deterioration, discoloration or other failures. Above is a ten-point checklist that will help achieve a lasting and discoloration-free plaster.

A Plastering 'Watch List' Taking control of the plastering process is within reach of any quality-oriented designer or builder, declares Kim Skinner. To help you on your way, he offers this step-by-step guide to managing what should happen on site before, during and after plaster application takes place.

Not All Color Pigments are Good for Pools It appears the plaster products that contain “organic” pigments become bleached (loss of color) over time when subjected to chlorine (an oxidizer). But products with “inorganic” pigments generally do not become bleached. Additionally, experiments which subjected both organic and inorganic pigments to LSI aggressive water showed that neither type of pigment lost their color from etching.

The Art of Good Pool Plaster Color An attractive plaster color (other than white) is often preferred by pool owners. However, it is very difficult for plasterers to produce a uniform and consistent color. The reality is that there will always be some minor shading (mottling) and variation in the color and can never be uniform looking like paint or fiberglass.

Why Acid Wash New Quartz Pool Finishes? It is understood that muriatic acid can dissolve and etch a plaster surface. Therefore, why, after a plastering finisher works hard to achieve a smooth, hard, brand-new, hand-crafted, quartz pool-finish, would anyone immediately perform an “acid wash or acid bath” on that pool and that plaster? Yes, doing so can increase the exposure of the quartz color; but isn’t that removing some plaster material and shortening the life of the plaster and leading to future problems?

New plaster on renovated pool- when to refill? Cement products need a certain amount of time to harden before being submerged in water, because it is very easy to dissolve the surface of fresh unhardened or uncured cement/plaster. I don’t see how anyone can disagree with that. In fact, the NPC's own plaster tests (Cal Poly-NPIRC) provided evidence and results of that fact. Therefore, shouldn’t homeowners try to request waiting a few hours before starting the water and reaching an agreement regarding the warranty?

Start-up Chemistry for Plaster Pools The effects of four different chemical startup procedures were studied.

• the “Acid” startup – where enough acid was added to lower the pH to 4.5 and alkalinity to zero - about 3 gals. of acid per 10,000 gallons of water
• the “pH-Neutral” startup – which equates to about one gallon of acid is added to about 10,000 gallons of water
• the “Traditional” startup - where the water is maintained with CSI balanced water; near zero or (0.0) CSI
• the "Bicarb" start-up - where the tap water is pre-treated with sodium bicarbonate to raise the TA to 300 ppm and the CSI is about +0.6 to +1.0

Pool Plaster Start-up Alternative Orenda Technologies has recently unveiled a new start-up program that is somewhat similar to the onBalance Bicarb start-up process. Instead of adding sodium bicarbonate, Orenda suggests adding calcium (calcium chloride) to low calcium tap water while filling brand-new plaster pools, which also like the Bicarb start-up, prevents the formation of plaster dust. We at onBalance have received numerous communications asking us if this calcium program is compatible with, or a viable alternative to the Bicarbonate Start-up Method that also prevents plaster dust. The answer is yes.

When Should Salt be Added? In our industry, there seems to be some consensus to wait 30 days before adding salt to new plaster pools, yet some say it is okay to add salt within a couple of days of filling the pool. Who is right? This thread describes why it appears that the recommendation to wait 30 days before adding any salt is appropriate for most plaster pools, including quartz and pebble pools.

Why no heater use for first 30 days? With new plaster there is a lot of plaster dust in the water and the pH is usually very high. When you heat water the potential for scale formation in the heater increases significantly. The actual timeframe for waiting to use the heater has no real merit. As long as the plaster dust is under control and the pH is in range there is no reason not to use it. Your risk of rushing to use the heater is scale clogging up the heater coil.

Installation Tips

• Take a sample from every batch of the plaster while it is being applied. Use plastic cups and write on the cup the date, time, address, and batch number. If there is a problem later, you can send the sample to the lab without having to take a core out of the pool.

• The CSI is not applicable to new plaster finishes under 30 days old. It is actually necessary, to achieve a smooth and dense surface, to have about a +0.5 CSI during the first 30 days. This is because the plaster (cement paste) surface contains about 20% calcium hydroxide, which is somewhat soluble in balanced and slightly positive CSI water and can be dissolved away. The plaster surface needs to be "carbonated" before the CSI should be lowered to the acceptable and balanced range. And that generally is achieved during the first month under balanced water.

• Pool owners can discuss these guidelines with their Builder or plastering sub-contractor and let them know that you understand some of these issues. When asking for bids, you can ask if they will follow the above guidelines. Some of them already do. The one that agrees should be the one you hire. You can watch them, make notes, film them, and even pay a little extra for them to slow down by not adding a high content of calcium chloride and adding water while troweling. It would well be worth the price. And one important thing I forgot to include in the above post, is to suggest to the pool owner to take two paper cups and scoop in two different plaster samples of a recently mixed and fresh plaster material (before it is applied to the pool and hardens) and keep for future analysis if something goes wrong.

• Pool owners can influence pool plasterers by simply telling them to not add more than 1 lb. of calcium chloride to 100 lbs. of cement, and telling them to not use excessive amounts of water while troweling towards to end of finishing. (They could sign a letter of statement for you). If plasterers time the troweling correctly and have enough personnel, they only need to lubriate their trowel slightly with some water, and perform the final troweling.

• On very hot and dry (non-humid) days, plasterers should place a tent or sun screen over the pool to slow down the hardening process, so that they don't need extra water to re-work the plaster.

• Tell your plasterer to make the plaster mix thick like oatmeal, and not soupy. Then take some pictures during the plastering process, then the plasterer will hopefully be extra careful to do the job correctly.

Plaster Start-Up Guides

See Plaster Start-Up Guides

Plaster Maintenance

The CSI is Reliable for Plaster-based Pools Using the Calcium Saturation Index (also known as the LSI in the pool industry) as a guide for maintaining proper pool water balance and to protect pool plaster, including quartz and pebble finishes, has become a mainstay in our industry for good reason.

All Plaster Finishes Should Last 20 Years All pool plaster finishes should last 20 years or more. However, some last only 5 to 7 years, and some less than a year before the plaster surface deteriorates, discolors, and looks terrible. Why the difference? Very often, plaster quality. Studies on pool plaster and cement/concrete flatwork have shown that poor workmanship practices have the greatest effect on durability, deterioration and discolorations. Various studies also confirm that water chemistry plays only a minor role.

Pool Water Balance is Not (Always) the Problem The Bottom Line - Maintaining slightly aggressive water (LSI or CSI of -0.1 to -0.5) is acceptable. It does not cause rapid plaster deterioration and discolorations problems on quality applied pool plaster. The plaster problems mentioned in the thread are prevented by following good workmanship standards. Right now, there are none.

Reducing High Calcium Levels in Pools By manipulating the water’s saturation chemistry, calcium can be removed via an ion exchange-style process of adding sodium to remove calcium, and then clear the water by filtration.

High CYA Levels Do Not Stain Plaster Contrary to some misinformation that has lately been floating around in the pool industry, high cyanuric acid (stabilizer) levels do not cause gray discoloration, or white spotting (“spot etching” as some incorrectly call it) in plaster swimming pools, no matter what. And there are several studies that have documented that.

The Zero Alkalinity Acid Treatment The concept of the “Zero Alkalinity” process (also known as a No drain Acid Wash) is to make pool water aggressive enough (by adding acid) to dissolve and remove stains or scale from cement-based plaster surfaces, including quartz and pebble swimming pools. Unfortunately, this process may remove some of the plaster surface material.

Plaster Problems

Being Blamed for Plaster Discolorations? Don't Get Hoodwinked Some newly plastered pools (including quartz and pebble finishes) may develop either white soft spotting (also called "spot etching" by some plasterers), streaking, calcium nodules, gray mottling discoloration, spalling (flaking), or severe craze (check) cracking within a few months after being plastered, and whoever has been maintaining the water is often incorrectly blamed for those plaster problems and defects.

Diagnosing Pool Plaster Problems

White Spotting of New Plaster Pools The problem of plaster spotting has been an ongoing puzzle and controversy in the swimming pool industry for over three decades. The generally round, smooth-yet-unsightly white soft spots in new plaster pools have long been a source of contention among pool plasterers, and pool chemical service firms or pool owners, each blaming the other for the phenomenon.

How White Pool Plaster Turns Blotchy This experiment below explains how white pool plaster can become blotchy gray, and also have white areas mixed into the gray areas.

How White Pool Plaster Can Turn Gray One would think that when mixing white cement with white limestone aggregate, the final pool plaster product would always be white. But that is not always the case. Unfortunately, white pool plaster sometimes turns gray (or grey) either immediately or a few months after the pool is filled with water. So what causes that to happen?

Calcium Nodules in pools What are calcium nodules? In swimming pools and spas, they are small mounds, bumps, deposits, or “slag” piles of calcium carbonate which are formed from material that has been released from the plaster. The small calcium nodules are rough to the touch, hard, and generally gritty. Nodules may form singularly (far apart or sporadically), or many and close together along a crack in the plaster surface.

Pool Plaster "Spalling" One of the arts or skills of the pool plastering trade is properly timing the troweling process. If troweling is performed when water is present on the surface of the plaster, forcing water back into the plaster paste causes excessively high water:cement ratios in the surface finish, weakening it.