Brown stains appearing on bottom of new pool?

[deelowe]

Not sure which forum to post this in.

I'm starting to get these brown spots all over the bottom of my pool. They are more prominent around the perimeter. For reference, the pool was installed in February and is on city water. There are no metal objects in the pool as the deep end has a step out and there aren't any hand rails. The pool is professionally cleaned weekly by the company who did the installation and we've been diligent about not letting leaves or other organics sit in the pool. The stains will sort of come up with a hard scrubbing, but not completely in most cases. At first we just had a few, but they appear to be growing in number. Again, mostly around the perimeter, near where the wall meets the base, but the spa and sun shelf have some on the bottom as well.

I apologize for the quality of the pics. The spots are much more obvious in person. Here's a link to an album with several photos: 12 new photos by dlow

These are my most recent maintenance reports according to the company we're using:

10/05/2020
5 ppm chlorine
8.0 pH
100 ppm alkalinity
240 ppm calcium
3400 ppm salt
1 gal muriatic acid

9/21/2020
5 ppm chlorine
7.6 pH
80 ppm alkalinity
280 ppm calcium
3000 ppm salt
40 % sanitizer output%

9/17/2020
5 ppm chlorine
8.0 pH
70 ppm alkalinity
250 ppm calcium
3000 ppm salt
18 filter psi

09/08/2020

5 ppm chlorine
8.0 pH
80 ppm alkalinity
230 ppm calcium
3600 ppm salt
60 % santizer output%
1 gal muratic acid

 

[mknauss]

Take some Vitamin C tablets, crush them up in a thin sock, and set on the brown stain. See if it disappears -- if so, it is iron. If not, find out if the pool service is adding any algaecides or other potions.

Your test data does not show a CYA level and it is obvious they do not have a proper test method to measure FC. We would strongly suggest you get your own proper test kit. Relying on a once a week 10 minute visit to manage your pool water chemistry and plaster longevity is not a good idea.

 

[deelowe]

Thank you for your help. I'll start learning how to do the pool chemistry myself. We were hesitant to do this initially b/c we didn't want the installer to blame us if there were any warranty claims. That said, we've had a lot of issues with this company's maintenance crew, so maybe it's time to start doing it ourselves.

Based on the evidence thus far, if it is iron, where could it come from? We're on city water.

 

[mknauss]

City water can have iron. It is not an EPA registered contanimant so your local water authority does not have to report it. It can build up. Also, do you have any lawn or bushes near by that could have been fertilized recently? Most fertilizers have iron in them.

 

[mknauss]

Also - call the pool builder. Since you felt you needed to use a maintanance company to satisfy the builder, then put it on them why you are getting staining.

 

[deelowe]

I have recently started a lawn treatment program. The timing seems relevant. Would the issue be that they are somehow spraying chemicals into the pool?

 

[mknauss]

Its possible. Solid product make more sense but enough liquid product may cause it too.

High pH and elevated FC can exacerbate iron staining.

 

[deelowe]

Thanks a ton. I'll start working on it and see what I come up with.

 

[JamesW]

Looks like iron from particles. Try the vitamin C.

What products are being broadcast near the pool?

 

[deelowe]

No idea. I'll call the weed treatment company and find out.

 

[JamesW]

Are you seeing any fertilizer product (dust/granules) on the deck?

 

[deelowe]

I've not noticed granules on the deck. We have seen some on the driveway, so I know they use some sort of solid fertilizer.

 

[JamesW]

Possibly getting in pool.

Maybe they blow off the deck with a leaf blower after broadcasting the fertilizer?

Are the granules on the driveway causing stains?

 

[Homebrewale]

Some fertilizers contain iron.

 

[deelowe]

Confirmed that their product doesn't have iron in it. Trying vit c tonight to see if it helps.

 

[deelowe]

Vitamin C works! Stains disappeared immediately. Now to figure out where the iron is coming from. Could it be something the pool company is doing?

 

[mknauss]

Not likely. With how the picture looked, I would say it is fertilizer. Regardless what the company said.

 

[deelowe]

Interesting. We'll see if it goes away now that the treatments are done for the year. At least I know how to fix it.