Some newly plastered pools (including quartz and pebble finishes) may develop either white spotting and 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.
Generally, it will be claimed that the pool water has been “aggressive” at some point in time, even if the water has never been aggressive. But more importantly, aggressive water does not cause the above plaster problems, and cement and plaster studies have actually determined that improper workmanship practices lead to those problems developing.
So why are these unfair accusations happening? One main reason is because the National Plasterers Council (NPC) doesn’t do anything to stop it, and in some ways, enables it to happen.
Let’s examine this issue. The NPC and some plaster inspectors define “balanced” pool water within very narrow parameters and limits, but without any supporting science to back it up. The NPC states that water parameters (pH, TA, CH) must be maintained within industry “Ideal” ranges to be considered balanced, and disregard the “minimum and maximum” standards.
For example, NPC literature essentially suggests that pool water with an alkalinity of 70 ppm is considered to be out of balance and aggressive, even if the other water parameters make the CSI balanced, the NPC still considers that water “aggressive” and able to cause plaster problems.
So if the water chemistry is being blamed as causing one of the above plaster problems, and a NPC inspector or plasterer gives you a copy of the NPC Technical Manual, or a report by Arch Chemical or Cal Poly (NPIRC), or APSP and other literature, and suggests that it proves whatever it is they are claiming; don’t be hoodwinked or intimidated. Those reports don’t prove that out-of-balanced water causes those problems. In fact, they mostly prove just the opposite.
Also, if the chemical start-up process is questioned by the plasterer because the tap (or fill) water was aggressive, we suggest that it is the plasterer’s responsibility to see that the tap water is balanced before it used to fill the pool. The vast majority of the damage (uniform etching) that is caused by aggressive tap water occurs while the pool is filling; and before someone shows up at poolside (after it is full) to balance the water.
Today, some plasterers (sadly) advertise that plaster only lasts 5 to 10 years. But not long ago, plaster used to be promoted as lasting 20 years. In reality, it still can and does last 20 years when quality workmanship is performed. It’s not difficult to figure out who benefits and who is harmed when plaster finishes don’t last very long.
It is unfortunate that poor quality plasterers are being helped to avoid being held responsible for bad plastering work and results. That needs to change for the betterment of the swimming pool industry.