The muriatic acid lowered the pH into a range where small amounts of chlorine is too much. How much of the chlorine in the water that is in it's active state is dependent on the pH.
For example, at a pH of 8 only 20% of the chlorine in the water is in the "killing form" as it is often called. At a pH of around 6.5, 100 % of the chlorine is in the killing form. When they told you to add a gallon of muriatic it lowered your pH enough to cause your chlorine to react to the iron.
One of the reasons I suggested raising your pH right away was to prevent your chlorine level from continuing to react with the iron. The other reason is that a pH below 7 is acidic and will react with any metal in your system especially the pool heater if you have one.
I believe I suggested raising to 7.2. Having thought about it I would continue to raise it to about 7.8. Once the reaction between chlorine and iron stops the pool will clear sooner.
On a side note, you already have iron in the water so the last thing you need is to add algaecides containing metals (copper).
I was hoping someone else with experience with brown water would chime in here. I've never dealt with turning a brown pool clear but I do understand the chemistry that brings it on.
Follow the directions on the sequestering agent you used. Small weekly doses are often called for.
Chris B wrote:I did not add the gallon of chlorine until after the water had turned brown. My chlorine level was at 1.2, ph was 7.8 and alk was 178 thats when the Watsons clown said to add all the muriatic acid. Thats when the water turned brown. I added the remaining 16oz of the sequestering agent this morning. It seems like the water lightened up a bit over night but not much.
How much is too much when it comes to adding additional sequestering agents? how long should I wait now since I added the second 16oz of the sequestering agent at about 6:00a.m. this morning?
Thanks for continuing to write back by the way, I really appreciate your time and help.