Swimming Pool Blog
by Rob Cox, March 04, 2011
Ensure a properly applied, cured and cared for Plaster Surface
Inground pools can have many different types of surfaces. Fiberglass, Vinyl, Plaster or PebbleTec. Plaster is the most common interior finish for many inground pools, and there are many choices of colors available. Colorants or Quartz additives can be added to the plaster mix to create interesting hues, and a more durable surface than the normal marble-based plaster mix. Additives also have the advantage of helping to hide minor imperfections or staining of your pool surface. Whichever pool plaster surface you choose, there are some tips to ensure a properly applied, cured and cared for plaster pool surface.
1. Plaster during the Cool Months: Plastering the pool in August, or whatever the hottest months in your area are, can cause the plaster to dry out prematurely, before it's filled with water. Check crazing or small cracks in the surface can occur as the air sucks the moisture out of the newly troweled plaster. Conversely, if a pool is plastered in very cold months, the plastering company will likely add a good bit of calcium, to create what's known as a "Hot Mix". This speeds up the cure of the pool plaster, and can cause some strength problems with your new plaster, creating soft spots. The best time of year would have temperatures in the 50-75 degree range, with higher levels of humidity in the air.
2. Fill the pool without stopping: If you can afford it, the best way to fill a newly plastered pool is from a truck or fire hydrant. Your new pool plaster will cure underwater, and it's important to fill quickly. Borrow a hose from the neighbor perhaps to accelerate the filling time. If the filling is stopped for even a few hours, you risk having a demarcation line, or a dirt line at that level.
3. Keep the pool clean: During the filling of a newly plastered pool, and for several weeks thereafter, do your best to keep the pool clean. Windblown dirt and leaves can leave stains on a fresh plaster job. With new plaster however, you are cautioned to not use a manual or automatic pool cleaner for several weeks. These can leave wheel marks on your new plaster - so, get out the pool brush and brush your pool daily, or twice a day if you can manage. Also make use of your pool skimmer net to keep the pool clean.
4. Acid Start the Pool: The "Acid Start" procedure is a method of lowering the Total Alkalinity level in the pool to near 0.0, so that the water will absorb the plaster dust. It also helps to cure the plaster fast. My process for this is to add 1 gallon of Muriatic Acid for every 5,000 gallons of water. You can add the acid as the pool fills, just be sure to wait until you have at least 5,000 gals in the pool, and be careful not to splash any acid directly on the plaster walls or floor. When full, check the Total Alkalinity levels to ensure at -0-, and then add Soda Ash, at a rate of 1lb per 5,000 gals, to bring the alkalinity level (and the pH level) back up. The process will take 1-2 days to complete. Brush the pool after each chemical addition.
5. Balance the pool water: And keep it balanced. New plaster will create a high pH condition, so you will need to add a pH reducer regularly during the first year, which means you will also need to adjust the Total Alkalinity just as regularly. Calcium Hardness levels should be maintained in the 200-400ppm range, to prevent your water from becoming agressive and trying to pull calcium out of your pool plaster. Low pH and alkalinity levels (after start-up) will also create agressive water, which can etch and pit your new pool plaster.