Pool stain / Fertilizer with Iron, Manganese, and Nitrogen

Stains on the pool surfaces, pool equipment
or on the swimmers, or off-color swimming pool
water. Discolored but clear pool water.

Pool stain / Fertilizer with Iron, Manganese, and Nitrogen

Postby SixFeetUnder » Thu 03 Sep, 2009 17:02

Hi all,

So for the most part my knowledge of chemistry and my major in it helps me with maintaining a pool, though I cannot say I know all the intricacies of pool chemicals/topic debates about what kills algae the best.

Recently, something freaking horrible happened while I was gardening. I was being a complete loon and some of the "VIGORO Ultra Turf Fertilizer" went into the pool. :thumbdown: We're talking just..... about 1/4 of a cup max around the edges, etc.

As soon as this happened, black black stains took over. Very very bad. : ( Clearly there is no mystery. Metals are in the pool. I decided to brush it off on the day, but I was sweaty and exhausted as is.... Brushing only settled the fertilizer granules in the center of the pool, whilst oxidizing the metals to flow out in a goo of major 'fucktastrophe,' as I like to call it. :thumbup:

I decided, after vacuuming to shock the pool the next day.


pH: 7.4
Alk: 120 ppm
FC: 2.0 (err....I just put trichlor tabs in my skimmer---as the box label allows for that and we don't want a floater in the pool as it doesn't exactly go in the skimmer).

The water cleared up genuinely, but there is still a problem of slightly murky water/cloudy while there are some stains...primarily yellowish/greenish stains. More yellow/brown than green to be honest...but I believe these are IRON stains. :wtf:

I know that Manganese are black so they can't be these yellow stains. Using vitamin C tab against them did absolutely nothing, same with chlorine against them. I'm in all honestly clueless what to do.

I'm thinking of getting Metal Free sequestering agent to chelate the pool. Along with this, probably a flocculent. But my main question is....exactly how do I get these stains out in specific (2 stains with small stains near the steps edges...small dot-like stains...). I will definitely use Metal free I suppose....but I need help from people here on these forums which I JUST found out about today...



APSI pools

Pool stain / Fertilizer with Iron, Manganese, and Nitrogen

Postby APSI pools » Fri 04 Sep, 2009 13:59

"I'm thinking of getting Metal Free sequestering agent to chelate the pool." That must be done first, a good sequestering agent would bring all solids including metals into solution. a metal removing chemical could help as it needs to be removed physically via filter. I would also test for Phosphates as it appears you accidently added phosphates via fertilizer. Vitamin C can work for wide spread staining, acid spot treatments might be needed. I would first try super shocking water with liquid chlorine and maintain 15-20 ppm free available chlorine for 7-10 days. This chlorine treatment is least intrusive and could oxidize stains before you try more entrusive chemical treatments. if you chose chlorine treatment first do not swim during treatment and then use Thiosulphate to reduce chlorine before swimming.

Pool stain / Fertilizer with Iron, Manganese, and Nitrogen

Postby SixFeetUnder » Fri 04 Sep, 2009 17:18

Thank you so much for your reply.

I actually got phosphate free fertilizer..or I'd be in big trouble with algae by now. Luckily no algae...I forgot to mention I had manually vacummed the pool the next day when this happened and used calcium hypochlorite to shock the pool, to kill off any food source, whilst brushing.

Luckily this would have taken care of any outbreak. I am more than likely going to add the agent for safe-keeping. I don't believe I will use a focculent as I said because quite frankly these are a rip off unless extreme circumstances bring me there. I use the B-B-B method as well...so I have liquid chlorine ready. I will probably raise it to 14 ppm (5 gallons at 6.0% FAC). That should take care of anything...hopefully these small dot-like polkadot stains go away... if not...I think I will just go with sandpaper than an acid wash....

Without PVC an acid wash is difficult...not to mention risky even with one. I personally don't like acid washes :thumbup:

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