I'm posting this in the Just Getting Started forum since most of the questions I've seen re problems with brown water in the pool and yellow water in a well that feeds it seem to be here.
I'm a newbie to TFP and certainly no chemist, but I have considerable experience with well water since that's all that I have (for both house and pool). If you are using well water and your pool water starts turning brown (and you haven't had a recent mudslide!), this may help.
The typical problem starts with the pool water turning brown (but not turbid), often after adding a heavy dose of chlorine. If your well water is faintly cloudy or yellowish, it's likely caused by dissolved iron, and mechanical filtering (like your pool's) can't remove it. There are only two ways to get the iron out: with an aeration system (expensive) and with aluminum sulfate (cheap). I've used aluminum sulfate for years with no problems.
When I first heard of the aluminum sulfate method, my first concern, of course, was safety. Can you really drink that stuff? It turns out that most municipal water treatment plants use aluminum sulfate, to remove dissolved material, so if it isn't safe, millions of people around the world are in trouble.
While the proper dosage depends on the concentration of iron (determined with readily-available test kits for well water), I've never needed more than 100ml (or about 1/2 cup) per 5000 liters of water. The chemical is sold in fine granular form and is added to the pool as follows:
- turn the filter on
- in a bucket, mix the aluminum sulfate with some pool water until it dissolves. (There will be a little residual grit that doesn't dissolve - no problem.)
- add the mixture thru the skimmer or in front of a return
- after a 1/2 hour, turn the filter off and leave it off for 12 hours. (This 'calm' time is very important.)
- when you come back, the bottom of your pool will be as brown as the water was. That's the iron that was pulled out by the chemical and sank to the bottom
- carefully vacuum out the iron
I think it's a good idea to do this treatment any time you add significant amounts of well water with iron in it, rather than letting it build to the point that the pool water turns brown.