A friend tells me "mercury free bleach" is a must...

[anderson110]

Otherwise mercury will accumulate in the pool.

Is there any credibility to this?

 

[Isaac-1]

It may have some credibility, however bleach is made through multiple industrial processes, and a quick google search showed that as of 7 years ago only 10% of bleach was still made with the mercury process (not sure if that was US or Worldwide though).

Ike

 

[JasonLion]

The entire industry has been in the process of phasing out the mercury production process for a long time. Clorox has been completely mercury free for over a decade.

 

[chem geek]

According to this article in 2007, there were only 4 chlorine plants left that used mercury while 115 do not.