Quote Originally Posted by JimK View Post
I would like to check my water to see if I still have metals and still need the sequestrant (I've been using The Purple Stuff for several years now), but according to Ben, it's seems sequestrants may interfere with the test results. So I guess the only way to find out if I still have metals (likely if the source is the salt as I suspect) is to stop using the sequestrant and see if staining returns. However, I really don't want to do that as getting rid of the stains is a royal pain and expense.
You can do a bucket test.

1. Take a CLEAN white 5 gallon plastic bucket with a lid
2. Add 4 gallons of pool water.
3. Add 1/4 cup of plain 6% Clorox bleach (~200 ppm chlorine)
4. Mix, cover and wait 24 hours.
5. Uncover, and check for sediment.
6. Add 1/8 cup washing soda (sodium carbonate)
7. Mix, cover and wait 24 hours.
8. Inspect for sediment and stains.

The high chlorine should break down the phosphonates, and may drop out any metals. If not, the high pH (washing soda) should finish the job. Perfectly still water should allow it to settle. It take very little iron (less than 0.5 ppm) to make visible sediment. The clean white plastic should make any stains or sediment very visible. Use Clorox, since cheap bleach may have some iron or other metals. I know Clorox filters to prevent this; I think the others do, but using Clorox lets you be fairly sure.

Also, I'm going to ask Sean, of AutoPilot to take a look at this thread.

Meanwhile, can you add full pool info to your signature pump / filter / SWCG make and model? Link in MY signature to the settings menu.