Acid Wash

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Acid washing the swimming pool’s plaster surface is a maintenance procedure that may be needed periodically throughout the life of a swimming pool.  However, since this procedure involves draining the swimming pool and applying chemicals to the plaster, there are certain risks involved which are not within the control of the acid wash applicator performing the acid wash.  The purpose of this statement is to provide you, the customer, with additional information about these procedures and inform you of some of the risks involved.

Normally, removal of water from a swimming pool causes no problems.  Listed below are a few things that can happen which you should be aware of.

  1. Hydrostatic pressure may cause the pool to rise out of the ground. Pools should not be left empty for more than 24 hours without relieving the hydrostatic pressure.
  2. Once exposed  to the air, tile may fall off the pool side walls.
  3. The plaster can shrink, expand, crack, blister, flake or pop off.

These problems do not normally occur, and are beyond the control of the person who has simply drained the water.  However, the possibility of these problems occurring is mitigated by not draining the pool after hard or prolonged rains nor leaving the pool empty for more than 4 hours.

The decision to use an acid washing procedure to remove stains from a pool’s plaster surface should be very carefully considered.  Under most circumstances staining takes many months or years to accumulate.  While acid washing is recognized as a safe procedure for removing stains, there are problems that may occur.

  1. Applying acid to plaster surfaces may cause the surface to etch, become rough or expose the aggregate in the plaster mix. To what degree this occurs depends on the concentration of acid, the temperament of the stain being removed, and the quality and condition of the plaster itself.  In some cases cracking, thinning or delamination of the plaster could be a preexisting condition and is beyond the control of the acid wash applicator.  Consideration should be given to our experience and if you have any doubts, seek a second opinion and/or additional information.
  2. An evenly colored, smooth texture after an acid procedure is a totally unrealistic expectation. The stains most likely took a long period of time to develop, and could be embedded deeply into the plaster material.  At best the customer can expect the pool’s appearance to look “brighter” than before, with some stains remaining.

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