Brown Rust spots?

COrtiz

New member
Jul 4, 2018
3
CYPRESS
Hi! First time posting hoping to get some help. Our pool/spa is 11 months old. 15k gallons, chlorine, Hayward cartridge filter, in Houston, TX, pebble tec. We've been using TFP since start up and have had zero problems I'm happy to report, only add liquid chlorine and acid (we have lots of water features that creep our pH up) on a regular basis. About one week ago we noticed a few brown spots. When we first opened the pool last year, we had a similar rust spot but noticed that there was actually a tiny shred of iron from the re bar that was poking through. Pool company came back and repaired that. So we suspected maybe it was similar, but there were more this time. Well today we notice that there are a lot more of them. I've attached a couple pictures, they're all on the deeper end and I tried brushing them away and they're not going anywhere. Water is crystal clear. I tested the water and went to Leslies just to verify my results. They're as follows:
My results using TF-100
FC 5
TA 70
pH 7.6
CH 300
CYA 40
results from Leslies:
FC 4
CH 230
CYA 40
TA 80
pH 7.5
Copper .2
Iron 0
Total dissolved solids 800
Phosphates 500

The lady said my metals were too high and recommended "Metal Free". My question is what could be causing these brownish rust spots and will Metal Free help. I don't want to start adding anything that is going to mess with my otherwise crystal clear, trouble free pool. Any suggestions would be greatly appreciated.
 

Attachments

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,231
Tucson, AZ
:wave: Welcome to TFP!!!

And grass nearby that was fertilized? Looks like little pieces of iron might have gotten into the pool. That is not likely copper staining and it is so localized, that using "Metal Free" or similar should not be needed. And forget about the phosphates.

Try putting a piece of Vitamin C on the slots and see if they go away to confirm iron.

I wonder if there might have been some contaminates in the plaster when it was installed?
Put on some goggles and get down there for a closer look.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
15,678
Tucson, AZ
Vitamin C to test for metals. Then a trichlor puck, quickly, maybe let it sit for 5 mins. If the trichlor gets it, then it could be black algae as that is how black algae starts. As Jason pointed out, someone slinging granular fertilizer around your pool could cause that pattern too.
 

COrtiz

New member
Jul 4, 2018
3
CYPRESS
As a matter of fact my husband does add all sorts of stuff to our grass often. He has a "tfp" like regime for lawns that he follows. I thought about it being the plaster, but the pool is almost a year old? I would think if it was the plaster it would have presented itself sooner. I did go down with goggles on Sunday when we noticed just 3 or 4 spots, and tried to scrub them out with the pool brush and got no where, definitely a reddish brown rust color. I sort of panicked today when I took a look and saw that they had spread. We've never had any algae at all, I never let the FC get below 3. So if I use vitamin C if it is iron, should that fix it (as long as the hubby doesn't spread anymore fertilizer in the pool)? I was just reading about an ascorbic acid treatment that seemed more involved. Thanks for the suggestions!!
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,231
Tucson, AZ
Correct. I don't think that is algae. Looks very much like he was careless and got some fertilizer in the pool.
The Vitamin C should pull the stain right off. You could crush a few in a sock and move the sock around to the various spots. Or swim down with the tablet in your hand and rub the spots.

Find out specifically what he just added to the grass and report back ... for curiosity sake. I wish someone would take care of my little patch of grass with TFP-like care.
 

COrtiz

New member
Jul 4, 2018
3
CYPRESS
Ha ha! The problem is, it's not as cheap as bleach and acid to take care of the lawn! He said he used Milorganite and it does indeed have iron in it. Mystery solved. Thanks so much for your help!