At wit's end about this particular staining issue

[cflannagan]

This is my 2nd swimming season following Trouble Free Pool practices. Last season, other than metallic staining which was not a significant issue (identified with help of people here in this forum), I had no trouble maintaining pool at all - it always looked great to swim in (I also added borates to our pool and maintained it at 50ppm).

So far this swimming season it has been off to a horrible start and I don't know what I could be doing wrong.

Per suggestions on this forum (you can see it in my post history), I started with ascorbic acid treatment of our pool when our chlorine level was 0.

The metallic staining that I had before seem to have gotten much better.

I then shocked pool for a week as per normal pool opening practices.

Yellowish-brown staining began to develop ALL over the pool. Because this happened shortly after my ascorbic acid treatment, I thought it was a side effect - probably metals being lifted off surfaces and then settling back down, this time, more scattered - but I also quickly got concerned, because it seems like staining was ALL over the pool, rather than "here and there spots". I added metal sequeserents for 2 weeks, but to no avail.

Basically, I sort of gave up on this staining issue (at this point I'm still thinking it's metallic), because we are eventually going to resurface the pool anyway with darker color. However, I still want to ensure I understand what is going on with our pool so we don't have the same issue - even if we're not going to notice it as much with a darker color surface.

Now we're at 2 months, and it seems yellow-brownish staining is still getting worse. This is all with my usual pool maintenance - numbers seem to indicate my pool is correctly balanced. I'm not getting it.

My wife thinks it's yellow mustard algae, but my chemical kit numbers does not seem to indicate anything- the "CC" numbers was 0.5 or lower. Plus, I took an overnight test once and it did not drop more than 0.5 overnight, so I don't think there is anything "alive" in my pool (which I think I would notice if there's algae).

However, after looking up symptoms of yellow mustard algae (which I understand is very frequently misdiagnosed), I'm not so sure anymore.

I have tried to re-identify whether or not what I have now is even metallic staining as I originally thought. I threw 4 Airborne tablets into pool and they sat on bottom of pool, fizzing away, but when they're gone, I don't think I noticed any real difference (no clean spots under where the tablet was).

Wondering if it's algae, I "reshocked" pool for a couple of days (high chlorine), but it doesn't seem to improve much.

What is complicating my ability to identify this is that I think I might be having combination of both issues: yellow mustard algae, and metallic staining as well.

I observed that some yellow-brownish areas was easy to brush off (they form on walls and bottom of pool), but there was also other yellow-brownish areas that I cannot brush off at all. I'm utterly confused now.

Latest pool numbers:

FC: 2.5 (will be pouring in more chlorine shortly, after giving muratric acid sufficient time to circulate thru pool - about 4 hours)
CC: 0.5
TC: 3.0
TA: 130
CH: 330
CYA: 35
pH: 7.8 (just poured some muratic acid in to resolve this)

Also attached pixs - apologies about the reflections, making it harder to see the issues. I might take nighttime pixs with pool lights on if I think it will help.

Help me identify this please! For the first time in a while, I don't know what I'm supposed to do next regarding our pool

 

[cflannagan]

more pixs.

The last pix in this post, is example of yellow-brownish areas building up on walls - it is easy to brush away, but not as easy as the areas shown in first pix of this post.

 

[JasonLion]

Mustard algae will always brush off, though it sometimes takes vigorous brushing. Metal stains will never brush off. From your description it sounds like you might have some of both.

An ascorbic acid treatment removes metal stains from the pool surface and puts the metals back in the water. You then need to use sequestrant to hold the metals in solution and keep them from redepositing as stains. Sequestrant breaks down slowly, so you need to add more regularly.

One good test for metal stains is to hold a vitamin C tablet against a stained area for 30 seconds to a minute. If the stain vanishes in that area then it is a metal stain, most likely iron. There are some kinds of metal stains that are not affected by vitamin c, but the yellow brown color you describe is almost always iron, which vitamin c does work on.

 

[cflannagan]

As mentioned in the original post, we used vitamin C Airborne tablets. We didn't notice any real difference (not as pronounced like the test I did last year to identify metal stains for the first time). But that might be because there's all algae under it.

I need some more definitive steps in resolving this growing issue. We have been brushing some of this stuff off, but if it were algae, is it just going to disappear from pool on its own?

I guess one possible approach is to try to remove all algae from pool (if I in fact have some of that) before seeing what's left (metallic staining) and try to handle it at that time.

I just don't understand why the stains we're able to brush off, if it's algae, seems to persist in our pool, even if our TFT100 kit does not seem to indicate organic issue with our pool (CC's never goes over 0.5, is usually 0)

 

[duraleigh]

It is possible to have live algae growth and have 0 cc's. It is a fairly common notion that the two (cc's and algae) must both be present if one is but that's not the case.

 

[JasonLion]

Take a look at the fighting mustard algae article in Pool School.

 

[cflannagan]

Good news, the algae problem is gone, at least for now. Indeed, I was having combination of two problems, the metallic staining, and the algae, thus complicating our attempts to identify it.

Continuing to "shock" the pool mustard algae level for a bit more (3rd day now), will probably taper off in one more day.

Will focus on the metallic staining later, it's not as urgent as the algae issue.

 

[duraleigh]

Just a note for the future....when you redo the plaster, I would take whatever steps necessary to bring in good water to fill your pool (without iron).

Iron stains on the pool surfaces is a very common problem here on the forum and can be VERY hard to solve. You end up being stuck with a lifetime of sequestrant dosing which costs more than to have good water trucked in.