Are you aware that the National Plasterers Council (NPC) has rejected APSP’s long-time Saturation Index (SI) standard of -0.3 to +0.5 for water balance? The NPC decreed in 2008 that pool water must be maintained within a Saturation Index (SI) range of 0.0 and +0.3. Negative index values are not allowed.
Interestingly, the NPC claims that they include other industry groups for input and consensus, yet, as far as we know, the NPC did not receive agreement from the APSP Recreational Water Quality committee (RWQ), APSP’s Technical committee, APSP’s Service Council, or pool service associations such as IPSSA and the UPA.
The NPC has also stated that they would “abide by the results obtained” from the research performed by the NPIRC at Cal Poly before policy changes are made. Yet, the NPIRC studies have not proven this new position of the NPC.
This type of thing also happened in 2003 when the NPC made changes to their Technical Manual, blaming improper water chemistry for several different plaster defects. Several pool industry members (including IPSSA) asked the NPC for supporting evidence for the Tech manual changes. The NPC did not provide any documentation.
When balancing water, is it not reasonable to allow for occasional negative indices to offset maintaining pool water with a positive SI? Is it not reasonable to allow for occasional negative indices in hard water areas of the country, or where calcium hypochlorite or bleach is used for sanitizing? Where is the proof that an occasional and slightly negative Saturation Index is detrimental to pool plaster?
In addition to their decree on the SI standard, the NPC narrowed other water balance parameters for service techs to follow. Instead of adopting APSP’s minimum and maximum values, the NPC wants to restrict all pool chemistry to only the ideal ranges – so instead of a calcium hardness standard of 150 to 1000 ppm, the NPC claims that 200 to 400 ppm of calcium hardness must be maintained. Instead of APSP’s total alkalinity standard of 60 to 180 ppm, the NPC requires that alkalinity of 80 to 120 ppm be maintained, and it must be “carbonate” alkalinity rather than “total alkalinity” as established by the APSP, making it even more restrictive. Also the pH is limited to a maximum of 7.6 instead of 7.8, and cyanuric acid is limited to 50 ppm instead of the maximum of 100 ppm.
So why has the NPC narrowed the chemistry parameters to a point where it is nearly impossible to maintain pool water within that standard, and to never allow for a negative SI? This especially coming from a trade association that stonewalls establishing standards for their own product… be it water:cement ratios, calcium chloride content, incompatible admixtures, etc. etc.
Consider this: NPC consultants are often called in to inspect a pool when a plastering job has developed some plaster problems, and the pool customer is complaining about it. The focus will likely be on water balance, and not on possible improper plastering workmanship issues.
Often, a water pool test (and also a tap water test) is performed and compared only with APSP’s National “Ideal” water balance standard as the required parameters to maintain, completely disregarding APSP’s “minimum and maximum” guidelines. If any water balance parameter is found to be outside the “Ideal” range, then consultants have been known to suggest that the “improper” water balance must have led to the plaster problem.
And in a stark contradiction, following the NPC’s official chemical startup procedure results in making new pool water aggressive (from -0.2 to -0.6 LSI according to their Start-up Card) during the first few weeks after initial fill… the most vulnerable time period for new plaster. This puts service techs in an awkward position.
More and more, it has recently come to our attention that pool plaster inspectors are (incorrectly) associating aggressive water (which, to them, means any negative SI, or any single low parameter) with plaster defects such as gray mottling discoloration, white streaking, soft spots, spalling or flaking, craze cracking, calcium nodules, delamination/bond failure, and even rebar rust stains. There are no plaster studies that support these claims. And this is not without consequence – pool owners and/or service techs are being made liable for replastering pools that the plastering company itself ruined!
Is it possible that the NPC adopted this new standard specifically to enable plaster consultants to blame “out-of-balance” water chemistry for various plaster defects, which then provides “cover” for their plastering members? Is this how the NPC “solves plaster issues?”
Comments
This stance from the NPC will make it particularly difficult for pools with saltwater chlorine generators since they often need to be run at a slightly negative saturation index to help avoid scaling in the salt cell. The use of 50 ppm Borates also helps with that, but having the saturation index at or above 0 will often lead to scaling since the pH at the hydrogen gas generation plate is much higher than the bulk pool water. Polarity reversal helps reduce the scale buildup, but does not eliminate it.
I wrote about the saturation index and some theoretical considerations in this post in the thread "Is the Saturation Index always Reliable?" where at first glance a saturation index of -0.3 looks scary since it implies a calcium carbonate product of concentrations that is half that of saturation and implies that the dissolving rate for plaster will be at half its maximum rate at that pH (maximum rate being with 0 calcium or carbonate). In practice, the actual rate may be influenced strongly by pH, circulation, and pH buffering (ironically where stronger buffering can be worse).
Brian, thank you for your comment. The NPC seems defiant to listen, discuss, or consider evidence that is contrary to what they want to believe. It has been nearly three years and they haven't provided any study to support or prove their positions on many water chemistry and plaster issues, and at least have a debate.
You may want to read my recent blog post titled "Salt Pool Blamed for Plaster Cracking and Nodules."
I have a propensity to agree with the conclusion of the article. The fact that my company is a standing member of both organizations has over the years given me perspective of the personality of each organization. When asking the NPC for assistance in determining root cause on plaster problems, they do not want to take a stand against poor pool plasterers. To have a tighter stand on chemical balance than what the standard that has been adopted, reinforces their member protection stance.