Rust stains

[anuoldman]

I've got about a dozen minor rust stains.... small curling lines in shape... my area / pool has high CH around 400 ...

I used a masonry finishing stone to rub one of them out, which worked but now there is a area of diamond brite that is a couple of shades whiter than the rest of the pool... it's drained right now anyway... should I?

a- rub down the whole pool with something to take off what I assume are the hard water coating throughout? if so, use what to sand such a large area consistently?
b- rub out just the rust stains and live with the lighter spots... it's too much trouble and I most likely won't notice when I refill the pool anyway...
c- some other choice I'm not thinking of

 

[Bama Rambler]

How about a vitamin C tablet on the stains while wet? See if that works for you.

 

[anuoldman]

thanks... ill try that....

you mean wet the area in question and put a vitamin C tablet on it directly?
is it a good idea to just sand the entire pool to brighten its appearance or not?
what would I use?

 

[Bama Rambler]

Yes, just wet the area and put the tablet right on it.
Sanding is something you'll have to decide if you want to do. That's a lot of work.

 

[JasonLion]

Vitamin C is definitely easier for iron stains than sanding/grinding. If it works locally you can either to all the other spots individually or treat the entire pool with ascorbic acid.

For calcium scaling in limited areas sanding/grinding is a reasonable choice. If the calium (hard water) stain/scale is extensive then you might want to do an acid wash instead of sanding.

 

[anuoldman]

any downsides to using abrasives on the surface? will removing the upper layer cause accelerated decay? do special considerations about water chemistry come into play? etc

 

[dmanb2b]

Plaster is semi-pourous and there is no telling how deep the stain is. If you can lift the metal stains with acid treatment, it is far more preferable than sanding down the surface and possibly not being able to remove the stain, or just have it re-appear in the same spot.

 

[JasonLion]

Any plaster you sand off shortens the life of the plaster. Calcium scale makes the surface thicker, so sanding scale off doesn't necessarily have much effect on the plaster, though it will almost always have some effect.

Plaster is usually applied reasonably thick, so taking off 1/16th of an inch isn't an immediate problem, but you can't do that very many times over the life of the plaster, and anything you do take off will shorten the life at least a little.