A very low pH (below 7.0) means the water is too acidic.  Acidic water commonly causes corrosion of pool equipment, rapid exhaustion of chlorine, and eye and skin irritation.

It’s common for pool water with low pH to appear crystal clear; however, the pool may now be very susceptible to staining.  This dramatically increases on vinyl or fiberglass pools.  In fact, fiberglass pools have an inherent attraction for metallic staining.


Staining and Low pH

You will need to ultimately adjust the pH, along with related Total Alkalinity.  However, before doing anything, the potential of staining must be addressed.  Acidic water can dissolve metals from your underwater light, pump, valves, heater, and other components.  A tiny amount of metal in the water is a staining problem.

As the pH rises into its proper range, metals in the water tend to precipitate out in the form of cloudy water and/or a uniform stain (plating) on the pool’s surface.  Even trace amounts of metals in the water can cause staining on some surfaces such as fiberglass.

There are no absolute solutions regarding staining.  The more iron or copper in the water, the more likely staining will occur as the pH is increased.  It is essential the pH be adjusted into its proper range of 7.3-7.7. 

In general, stains are often prevented as follows:

1.  Add 1 oz. of Pool Baron's Super Metal-X for each 1,000 gal of water.  For example, add 25 oz. for a 25,000 gal pool.

2.  Do not superchlorinate or shock the pool until the pH has been back in proper range for at least 48 hours.  Afterwards, we suggest shocking only with Pool Baron's White Lightnin' non-chlorine shock.

3.  Adjust the Total Alkalinity to 80-120 ppm.  Add no more than 8 lb of Pool Baron's Alkalinity Increaser every 6 hours.  This process will also slightly raise the pH.

4.  Test the pH and slowly raise it into range.  Add 1-2 lb of Pool Baron's pH Up every 6 hours, and check pH until you achieve a pH of 7.3-7.7.

5.  After pH is in its proper range, add METAL-X PLUS according to instructions or Pool Baron's Natural Clarifier to remove the metals if more than 0.4 ppm of iron or copper still remains in the water.

Most stains can be removed, but it may require time and some investment in chemicals.


Related Articles:

Understanding Metal Stains

Removing Metal Stains

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