I would like to get some input as to an issue that occured with a neighbor's pool. The pool is standard freshwater with a DE filter, raised wall with flagstone in rear and flagstone around waterline. They contracted a reputable company to remove the calcium buildup on the stone and to acid wash pool. The crew did a great job on the stone using red garnet and afterwards did an acid wash on the quartzscape. When the contractor finished and was putting CYA in skimmer, apparently it came back out via the returns. The filter is a Pentair FNS with obvious openings in the grids or manifold.
Questions is, is there anyway for the stone cleaning and acid wash process to blame for damage to the filter grids? The contractor did use a deck pump to get most of the red garnet out, however there was some in the filter when it was opened. A trash pump was used to drain the water/acid out. The neighbor is blaming the contractor and asking them to pay for the new grids which their pool maintenance company is telling the neighbor everything was fine before the stone cleaning.