Iron in water source

[BigDave]

I agree with PoolDoc. That's algae.
It seems like you can put a lot of chlorine in the water with those cal-hypo tabs. I'd use them and bleach to get the FC to 10-15 and keep it there until the green turns blue.

[PoolDoc]

What he said . . .

[CarlD]

As I've gone back and read this thread two things pop out at me:
1) Ben said bring pH down to 7.0 yet BD and FBU kept insisting it should be between 7.8 and 8.0 so it precipitates. Yet I thought the point of the cal-hypo was to get the dissolved metal to stick to the calcium and be captured in the filter. I'm confused by this.
2) It's no surprise that when you use large amounts of Polyquat your FC drops like a stone. A quart in a roughly 20k pool will drop FC from shock levels to very low levels, 1-2ppm in 48 hours. It's always something to be aware of.

BTW, that's the "ugly" green of algae, not the "pretty" green of metals.

Ben, Lisa recently found the old thread of a couple who invented a filter gadget that does the same thing as the auxiliary Intex pool....a filter system of lots of quilting batting that sucked the metal right up! I THINK it was using a five gallon bucket with a lid, a submersible pump and some hose.

[BigDave]

@CarlD: I'm pretty sure that dropping the pH is for starting the metal removal process and get and precipitated metals into solution. Next step is holding them in solution with HEDP. Then remove metals with CuLater or using cal-hypo in the skimmer to encourage metals to come out on the filter by creating a high chlorine / high pH zone before he filter.

[CarlD]

@CarlD: I'm pretty sure that dropping the pH is for starting the metal removal process and get and precipitated metals into solution. Next step is holding them in solution with HEDP. Then remove metals with CuLater or using cal-hypo in the skimmer to encourage metals to come out on the filter by creating a high chlorine / high pH zone before he filter.

That's what I thought, but I thought the high FC/pH was to be local to the skimmer, not the whole pool.

[stcohen]

During the process actually backwashed a total of 4 times that produced what looked like rust. Pool was improving then turned dense green. Did not think algae with the high FC and polquat. Did notice a pH drop day after using polyquat-just brought it back up with cal-hypo. Today
pH 7.6
FC 14
Still green, maybe a little less dense. Placed a Culator in trap in case residual Fe.

[CarlD]

Polyquat isn't acidic, as far as I know. It WILL drop FC. However, if FC is very high, it causes a false high pH reading--we warn against this all the time. When Polyquat brought the FC far down, the apparent lowering of pH would simple be a true reading.

[PoolDoc]

I didn't go back and re-read, so I'm not sure what I said.

But normally, you'd want to manage metal removal by STARTING at low pH, with HEDP present, and then gradually allowing pH to move upwards as cal hypo is used.

The goal is to FIRST get the metal dissolved (Vit. C with no chlorine), SECOND to keep it dissolved (low pH + HEDP), and then THIRD to gradually remove it on the filter, while avoiding sudden changes in pH or FC that could re-stain the pool (gradually increasing pH & FC + cal hypo upstream of the filter).