Concrete Pool Maintenance Tips
Concrete pools are generally finished with plaster,
an age old process of finishing many structures. Used
underwater it provides the watertight seal that the
more porous shotcrete beneath it cannot. Plaster finishes
provide twenty years of service under ideal conditions,
however ours is rarely an ideal world. The plaster surface
is meant to degrade slowly, eventually requiring a fresh
coat.
Barring problems in the mixing, application and curing
processes, the pool owner 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
Alkalinity should be kept between 80 - 120 ppm.
Lower levels may etch your plaster, which provides a
safe harbor for dirt and algae to grow, isn't attractive
and is rough to the touch.
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.
Common Concrete Pool Problems
Pool plaster is pitted or
etched (see picture below)
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 concrete 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.
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