Brown/Black Stains

[Wrobert]

This is our first year with our new pool and we already have some stains. I took the mesh cover off after winter and saw the rock and plaster had these stains on them. What is it and how can I prevent it? Is it something leaching out of the stone or mold/mildew/algae growing or what? The pictures don't show it but the stain in the pool runs directly under the stone. (The dark spots near the waters edge is just water drops)

Also, on a slightly different note and possibly should be a different thread: The pools been open for a little over a month now; I have a couple of small stains forming below the waterline blackish/browish very light, won't scrub off with pool brush. My FC dropped to 1-.5 a couple of times when I was trying to get my CYA under control (slowly bringing it up, 25-30 right now), but I've been on top of it lately with my FC 2 or higher and my CC never above .5 if they register at all. I've done a OCLT a few times and it shows no chlorine being used. Possibly algae? Should I slam to be sure? When the pool was originally plastered and filled, within a few day a streaking brown stain formed at the bottom of the deep end. The installers came out and took a hose and acid washed it away. I'm now seeing it has slightly returned. Is something pushing its way through the plaster and the small stains at the waterline the same thing?? Help.

 

[Casey]

Hello Wrobert!

Can you please post a full set of test results?

 

[Wrobert]

Here are the last test results I did this morning:
FC 4.5
CC <.5
TA 110
CH 250
CYA 25-30
pH 7.8

Thanks

 

[Casey]

I would see if a vit c tablet held onto the stain lifts them.

Also, your pH is high and needs brought down.

 

[Wrobert]

Just got the vit c tablets... They took the stain off.... Wow! I just reached over the side and rubbed the tabs like an eraser and they just erased the stains. I couldn't believe it came off so easy.

Adjusted the pH also after, down to about 7.4-7.5

Thanks!!

 

[duraleigh]

That vitamin C test pretty much confirms those are metal stains......almost surely iron.

It would be a good idea to have your water tested for iron at a pool store or do so yourself with the Taylor K-1716. (It's pricey)

Are you filling from a well?

 

[Wrobert]

I'll see about getting the water tested for iron.

It was originally filled last fall by a water truck that got the water from a city water hydrant. I ended up having to put in about 1000 gallons from our well this spring.