Iron contamination - about to drain & refill, what about the sand in my filter ?

[Bubba]

Somehow a steel rod spent the winter in my pool .
Pool is algae free (OCLT test) and still very green (can't see the bottom).
I've confirmed the presence of iron with asorbic acid on the brown stains on my white steps but I can't see how much of the rest of the pool has stains.

Safe choice seems to be treat the pool with Asorbic Acid (I'm using 2lbs for 24k gallons), run on recirculate overnight and then drain/refill.
FC will be close to 0 by the time I add Asorbic Acid.

My fill water is iron free.

Questions I have:
1) Since I can't see the bottom or sides of the pool I can't tell if/when everything is stain free.
Is there anything I can do to ensure any stains are gone before I drain? Run pool cleaner ? Brush sides ? Run on recirculate for longer? Use more Asorbic Acid? ..???

2) Should I also replace the sand in my filter to ensure no iron gets back into the pool ?

TIA

 

[Texas Splash]

Normally the rule is treat for algae first, iron second. This also helps when the staining is wide-spread requiring the AA treatment as opposed to spot treatments for isolated areas. For an AA treatment, you want a good visual of the pool surfaces to know how the AA treatment is progressing. It's a bit unfortunate you have to use chlorine to perform the SLAM since you plan on doing a major exchange anyway, but I don't see any other way to do a wide-spread iron staining treatment other than having the pool full for the AA, then draining. Having clear water to perform the AA is an unfortunate necessity I'm thinking.

Oh, and I wouldn't worry about the sand.

 

[Bubba]

I already slammed the pool, no signs of algae in skimmer sock or pool cleaner, over night FC test shows nothing growing, still can't see the bottom of pool.

 

[Texas Splash]

over night FC test shows nothing growing

Okay. Normally if someone passes the Overnight Chlorine Loss Test I wouldn't worry too much, but it's odd your water is still cloudy. How old is that filter? Have you opened it up lately to check see if the sand could use a deep clean? Did you happen to test your CC level? Since passing the SLAM requires passing the OCLT, CC of 0.5 or less, and clear water, I would be inclined to continue the SLAM until you see better results and pass all 3 SLAM criteria.

 

[Bubba]

I did a 30min deep clean on the filter, CC is barely 0.5.
Are you saying that there's no chance that the iron would make the pool water green and cloudy?

 

[Texas Splash]

Green, it could depending on the pool color. Cloudy - no.

 

[Mdragger88]

Green maybe but not likely keeping it cloudy.
The polyfill trick only works on oxidized iron which is what occurs when chlorine is added to the water so raising fc to slam level is part of the polyfill filtering method.
The slam & polyfill can be done at the same time.
If you don’t ensure you’re algae free & have to slam after you refill you may cause more stains. So its best to complete the
SLAM Process now.

Got any pics of the current condition?
What are your latest test results?

 

[Bubba]

FC is steady at 4.0 (with salt water generator running)
CYA 10
TA 10
PH 6.8

I added 2 lbs Asorbic Acid which cleaned up my steps beautifully, can't see bottom of the pool to verify what that looks like.
CYA, TA and PH are low because of rain and backwashing during slam (PH possibly also due to asorbic acid). Have not raised them since I'm still expecting to drain the pool - pending advice here.
Overnight test was steady at 4.0 FC, 0.5 CC (salt water gen off).

 

[Texas Splash]

Well, even though you are planning to drain, I wouldn't leave the pH that low nor would I want the CYA that low. You not only have no FC protection from the sun, but the chlorine is less buffered and more intense in the water which could aggravate the iron more. Cloudy water is always a concern (algae). The steps on this one treatment plan have been a bit unconventional, so use your own judgement as to when you wish to do the drain and refill. The sooner the better I suspect as the cloudiness may get worse unless you back into a full-blown SLAM again.

 

[Darin]

How many days have your been filtering? Just because you don't have algae alive does not mean that the water will be clear. During opening my water is cloudy for 4-5 days before the sand filter collects all of the dead algae and this is after i pass the overnite test.

As far as the iron rod in the pool, it will not oxidize enough to make your entire pool off color. As far as the iron stain. put a half cup of powdered iron out in an old sock and rub the stain. It will come right out.

 

[Darin]

2) Should I also replace the sand in my filter to ensure no iron gets back into the pool ?

NO. sand has nothing to do with it.

 

[Bubba]

How many days have your been filtering? Just because you don't have algae alive does not mean that the water will be clear. During opening my water is cloudy for 4-5 days before the sand filter collects all of the dead algae and this is after i pass the overnite test.

As far as the iron rod in the pool, it will not oxidize enough to make your entire pool off color. As far as the iron stain. put a half cup of powdered iron out in an old sock and rub the stain. It will come right out.

Been filtering for about 2 weeks as well as running pool cleaner and skimmer sock. No visible signs of dead algae in pool cleaner or skimmer sock.

 

[Darin]

When you backwash your filter, is it brownish in color? That is dead algae.

 

[Darin]

skimmer sock.

sock wont do anything to collect dead algae. It is the filter that does the work after the chlorine kills it.
How long have you run it since you completed the SLAM? Your CYA is too low. You really need to follow the SLAM regime.

 

[Bubba]

Definitely not brown, not green either. looks the same as the pool water, cloudy.

I disconnected salt water generator and the water in there (post filter) looks exactly the same.
No visible particles in suspension.
I filtered the water through a kitchen paper towel (multiple times), looks the same.
I took water straight out of the pool and compared to filtered water above, looks the same (see pic)

 

[Bubba]

I'm thinking that either the filter is not working properly or there is nothing in suspension.
The filter was definitely catching algae during the SLAM so it's doing something.

 

[Bubba]

Unless it's normal for filter output to not be totally clear ?

 

[Darin]

If SLAM'ed properly it will filter to clear. It sometimes takes awhile.. I backwash 2 to 3 times a day as well as manual vac every day until clear. Might take 7 days, this year 6 days.

 

[Bubba]

Ok, I'm going to raise my CYA etc. and do another slam to be sure.

 

[Bubba]

So I slammed it again.
Easily passed overnight drop test on the first night and every time since (FC & CC) but pool is still not clear.
Backwash water appears to be clear, even after 2 days running 24/7.

CYA 30
TA 60
pH 7.2
FC 13
CC < 0.5

Do we still think it's algae?

I did a deep clean on filter and checked the spider gasket. Should I replace sand? add DE ? Replace the water? Something else ?