Interesting Solution to Iron Problem - need advise

[tlhwxman]

Hello all,

I have been posting my woes regarding iron staining for a few months now (http://www.troublefreepool.com/yellow-brown-staining-problem-t43712.html). So far, TFP has been a huge resource. I have tried everything that was suggested on this site and more. After all this effort I am 99% positive of two things. #1 - I have a high level of dissolved (ferrous) iron in my pool. #2 - All efforts to sequester this iron for longer than 4 days has failed.

An interesting solution has been suggested to me by the pool company that originally installed the pool (and does repairs for us now and then). They have no "skin in the game" so to speak as they do not sell chemicals. They seem sincere and knowledgeable. Anyway, here was their solution.

1) Drop CYA to 40-50
2) Keep FC between 1.0 - 1.5

They state this is acceptable to sanitize the pool and will keep the FC low enough to prevent the iron from precipitating out. The FC numbers seem to come close to the Chlorine/CYA Chart by Chemgeek

What say you all??? I would like to have the thoughts of folks on this forum about this particular solution. Fire away.

Thanks in advance
Todd

 

[tlhwxman]

BTW, Just to be clear:
The solution in my original post was a meant to be permanent, meaning I would keep those numbers there forever (i.e. CYA 40-50, FC 1.0-1.5).

Just wanted to clarify

 

[jblizzle]

Anyway, here was their solution.

1) Drop CYA to 40-50
2) Keep FC between 1.0 - 1.5

That may prevent you from getting metal staining, but your pool will likely turn green instead due to algae.

They state this is acceptable to sanitize the pool and will keep the FC low enough to prevent the iron from precipitating out. The FC numbers seem to come close to the Chlorine/CYA Chart by Chemgeek

Those numbers do not look very close to me to the Chart ... the minimum FC level for a 40ppm CYA is 3.0ppm ... double to triple what the pool builder suggested. {EDIT2: I missed the mention of the SWG ... and can see the logic of trying to interpolate below the SWG table levels. I still think that FC recommendation is too low, at best you would be on the razor line of the minimum ... and are you sure your SWG could keep up with the FC losses to the sun if the CYA were lowered?}


EDIT: What pH are you maintaining?

 

[UnderWaterVanya]

#1 - I have a high level of dissolved (ferrous) iron in my pool. #2 - All efforts to sequester this iron for longer than 4 days has failed.

An interesting solution has been suggested to me by the pool company that originally installed the pool (and does repairs for us now and then).

1) Drop CYA to 40-50
2) Keep FC between 1.0 - 1.5

They state this is acceptable to sanitize the pool and will keep the FC low enough to prevent the iron from precipitating out. The FC numbers seem to come close to the Chlorine/CYA Chart by Chemgeek

I have no special knowledge so please bear with me.

How does 1-1.5 seem close to the CYA chart?

40ppm w/o SWG = Minimum 3, with Target of 5.
50ppm w/o SWG = Min 4, Target 6
60ppm w/o SWG = Min 5, Target 7

The SWG chart starts at 60ppm:
60ppm w/SWG = Min 3, Target 4
70ppm w/SWG = Min 4, Target 5

Let's assume just for grins that the minimm/target FC requirement dropped 1 point for 15 points of CYA. It looks more complicated but that's just a swag:

at 45ppm w/SWG = Min 2, Target 3 which is about 100% of the FC that your being told to use. PLUS the SWG will be working overtime to keep up due to the lower than recommended CYA.

 

[UnderWaterVanya]

If someone wiser would comment maybe you could get by with that setup and Polyquat 60. It's not something I have any experience with - just thought you might want to explore that with ChemGeek or someone if the tradtional options for metal have failed for you.

 

[tlhwxman]

@Jason (jblizzle) - yes, I have a SWG so I adjusted for the numbers in the CYA/FC chart. My pH is kept between 6.8 and 7.2 (to try and control the iron - doesn't work). I should also add that I have followed the Iron treatment process to the letter. Over the last few months I have done the suggested AA treatment (multiple times). I also have a Sequestering Test kit and have maintained all the way to ~200% of the recommended maintenance dose (~16ppm). Even at that level of sequesterant, I was adding 1 - 32 oz bottle a week! I was using Jack's purple if you were wondering.

1 bottle of Jacks Purple a week tells me something is wrong. There is something else in play here. Which is why I am willing to try something different at this point. The suggested FC levels made me suspicious, which is why I am here.

The people that own the pool company swear that they keep these levels in their own pool. But I can't see how that is possible without an Algaecide.

Todd