Pool Info: Plaster Pools - Page 2
Plaster Pools (cont.)
Want to increase the life of your plaster?
Barring problems in the mixing, application and curing processes, the pool owner, or service company controls its condition and life span. Keeping your water chemistry in balance and most importantly, preventing corrosive water environments of low pH and low alkalinity will reduce wear and tear.
Maintain your pH levels at between 7.4 - 7.8.
Heavy metals cause stains.
Metallic salts cause scale. These salts are primarily forms of calcium and magnesium which can deposit on your plaster, pipes and equipment. They may arise from the use of calcium based sanitizers or the fill water may have high calcium hardness levels.
Keep your calcium hardness levels between 200 - 400 ppm.
A level that is above this may find it easy to precipitate out of solution. This is known as a scaling condition. Conversely, water with low levels of hardness will produce an aggressive condition. In aggressive conditions (soft water), the water will take the calcium it wants directly out of your plaster, resulting in plaster breakdown and bond failure.
Pool plaster is pitted or etched?
If your plaster has surface irregularities, which may take on a beige hue, you have what's commonly called etching. This etching can be caused by low pH or alkalinity; an acidic condition. It may begin within the plaster, from the original mix on application, or etching may start from the gunite side of the plaster and work itself from the outside in.
Pool plaster has large, dark areas?
You may be seeing the gunite or shotcrete beneath the plaster beginning to show through. You better start budgeting for that re-plaster.
Pool plaster has small cracks?
Known as crazing or checking, the tiny, barely visible cracks are usually caused by extreme temperature variations, especially during initial curing. These are not actually cracks, and pose no structural hazard or danger of leaking. Acid washing could remove the crazed layer. Larger cracks should be cut out in a butterfly or dovetail fashion with a 4" or 7" grinder, and filled with a plaster patch mix or a flexible sealant can be used where further movement is suspected.
Plaster has delaminated?
Known as bond failure, this will occur as areas where the plaster has popped off. Usually seen on re-plaster jobs, where the plaster to plaster bond may never be as strong as the original plaster to concrete bond. This is repaired with a plaster patch. Plaster normally does not delaminate from the gunite; this bond failure can more easily occur, plaster to plaster. Chip away any loose material around the edge of the delaminated area. This will sometimes make the patch much bigger than the hole is to begin with. Chip & chisel to break up and rough up the surface, clean and brush on a bonding additive. Then pour in premixed white Portland cement and marble dust; 2:1. Use bonding additive (like Acryl 60) to mix the plaster with. Trowel smooth with a round ended trowel. Keep the patch from drying too quickly by doing this repair in the evening and covering with moist towels or burlap.
Plaster patching: The delaminated area is chipped outwards until good bond is found. The surface is roughened and plastered is troweled in place by hand. Cost depends on the size and location of the patch. Plaster patching material can be purchased at most pool stores. It is a mixture of white Portland cement and marble dust. A bonding additive such as Acryl 60 should be used when applying.
Re-plastering: The pool is drained and acid etched several times. Chipping and cutting around all fittings and under the tile allows the new coat to be feathered. A scratch coat is applied first, followed by a finish coat. The pool is filled immediately; the plaster cures underwater. The surface must then be brushed twice daily, with vacuuming and continuous filtering to remove the plaster dust. Cost for a re-plaster is based on surface square footage. Expect $2,500 - $4,000.
Once upon a time, plasterers would plaster a pool in any color, as long as it was white. Black or gray plaster is now becoming more common, and other colored additives can produce varied color effects. Any colored plaster will show more mottling than white pools, however. If you plaster in any color other than white, expect streaking and uneven hues. Don't expect flat black color, for example.
Pool painting: Before plastering became popular, pool shells were painted. These were low grade paints that barely lasted one season. The annual drain & paint was gladly given up when plaster became popular. The underwater epoxies used today offer a 7 year life span for about half the cost of re-plastering. Paint adheres very well to properly prepped plaster, and offers a wide variety of colors and graphic capabilities. Pool painting is a second class choice to re-plastering. It may be half the cost, but will last only half as long (at best). If you start painting, you keep painting, unless you sandblast it off to allow re-plastering. We tend to discourage our customers from painting a pool. A few dollars saved in the short run will cost more in the long run.
Pool painting: The pool is drained and degreased. It is then acid etched and degreased again. After drying, a primer coat is applied, followed by two coats of the chosen color(s). Again with the drying, and the pool is filled. Price will vary according to size and prep factors. Expect $1,900 - $2,800. Pool artwork varies.
Want to Re-plaster the pool yourself?
I would discourage this. Plastering is nothing short of an art and science. Experienced.... (continued.....)