Brownish-gray stains in vinyl IG pool

[gumbeaux71]

Hi all,
Has anyone dealt with brownish-gray staining in their vinyl-lined pools? (See attached photo.)

Opened the pool and had a minor mustard algae problem and lots of staining at the bottom of the pool.

I quickly resolved the algae problem with one dose of Yellow Out, but my first shock attempt did not resolve the staining problem.

Pool is vinyl, IG and has no heater. Put some Ph Down in a sock and rubbed onto the stain, which seemed to get some of it up, though very gradually and not enough to actually see the color of the liner underneath. I lowered PH to 6.8 and let chlorine go to 0 in anticipation of using some ascorbic acid on the stains. However, I just tested the ascorbic acid and that didn't seem to remove the staining.

I'm not sure where to turn and what to try next! HELP!

Thanks,
Erica

[gumbeaux71]

Hello again. Can anyone give me advice on my staining problem? Other things to know are that my TA is 90 and that my calcium does run high.

Thanks in advance!
Erica

[DavidD]

Erica,

In my opinion, those do not appear to be metal stains. As far as I know, Ascorbic acid is generally only used for metal stains and sometimes calcium deposits. I believe this may be black algae or some residue from algae. You say you lowered the PH to 6.8, Why? That is a dangerous thing to do since most testers only test down to 6.8 so your PH may in fact be lower which is not good for your liner.

Also, post some additional numbers for FC (free chlorine), CC (combined chlorine), CYA , along with PH & ALK. and let's see if you have any thing that is chewing up the chlorine. I'll bet someone here more familiar with vinyl liners has seen this before.

Dave

[JohnT]

My first thought on seeing the picture is they are marks made by leaves laying on the bottom.

[gumbeaux71]

Thanks all for your input. Those stains could indeed have been caused by leaves as the pool basically sat during the winter months. It was covered, but there was still some debris in the water when we uncovered. Also, I was just seeing the beginnings of mustard algae, so I used some Yellow Treat, brushed, shocked, and ran filter appropriately.

My pool's PH generally stays around 7.4 - 7.6. However, I read in a couple of places that the PH should be lowered and chlorine discharged (used up) before using ascorbic acid. At the time of my post, I really thought this was some kind of stain caused by metal, but trying the ascorbic acid didn't help. That's when I figured it was a non-metal stain. However, I am pretty certain it's not black algae, as I had dealt with a few spots of that in my spa a few years ago.

To make a long story longer, I shocked last night and the stains seemed much, much lighter this a.m. I'll continue that route, I guess.

I will post my numbers when I get home and test the water. I'm still puzzled as to what caused such bad staining. I guess it could have been leaves...

[gumbeaux71]

Hi Dave,
Here are my numbers from this evening:
FC .5
CC 0
TA 90
CYA 40
Ph 7.2

I shocked to 10ppm last night. You are right that something is eating up my chlorine!

[smallpooldad]

Dave,

I had the same problem. My pool is gunite - 9,000 gals.

The ascorbic acid ( 1 lb in my pool) treatment outlined by Maria (Mbar) in one of her posts only worked when I got my ph down to 6.0. Use Ben's program to see what your acid needs are for your size pool. No damage was done to the pool, but boy did it look great after the treatment.

Make sure your chlorine is at zero before you start or all you will be doing with the ascorbic acid is useing it up to eat the chlorine and not cleaning the pool.

As ascorbic acid puts the iron/calcium into to solution and does not precipitate it is important that you use an agent such as metal out ( 3 quarts in my pool ) to get it out to your filter. If you have a sand filter (mine is 300 lbs), then put in 1/3 lb to 1/2 lb of DE to help it get trapped. I use the blue stuff it helps precipitate the metals.

If your filter clogs run the backwash for a minute, no longer, as you want to keep the filter heavy on the DE to trap the metals. The best solution would be to completely drain the pool after 24 to 48 hours as this would take out all the solution.

Hope this helps.

[smallpooldad]

Dave,

Sorry forgot one thing. Ascorbic acid eats up the chlorine and if you are not emptying your pool you will need to add A LOT of chlorine, before it takes. If you used Algaeside 60 you might get a false reading stating you have no chlorine when in fact you do, this will go away after 24 to 48 hours.

Aloha

[waterbear]

Hi all,


Opened the pool and had a minor mustard algae problem and lots of staining at the bottom of the pool.

I quickly resolved the algae problem with one dose of Yellow Out, but my first shock attempt did not resolve the staining problem.





I shocked to 10ppm last night. You are right that something is eating up my chlorine!


Check out this thread. might also help explain your low chlorine levels
http://www.poolforum.com/pf2/showthread.php?p=7384#post7384

[DavidD]

smallpooldad,

You brought your PH down to 6.0? That is way too low to be suggesting anyone ever do in my opinion. I think you misunderstood Marie if you thought that was what she was suggesting or you meant to say 7.0. As far as I can recall, no one here has ever recommended anybody lower their PH below 7.0.
I've done the "ascorbic acid treatment" multiple times with great success. I have never lowered my PH below 7.2 prior to using since it will in itself lower PH. Erica (the original poster) does not have a metal stain after all. It is most likely leaf stains as John surmised or possibly algae. As Evan pointed out, her chlorine demand most likely stems from the Yellow out.

Erica,
You seam to be right on track now. I would suggest you only use Yellow out or these other products only as a LAST resort. Ben has stated in the past that "Using either Yellow-Out or Mustard Master will temporarily eliminate ALL free chlorine, replacing it with a chloramine, monochloramine. OTO will show a high chlorine level, DPD will show none at all" so it seams to me that if this wee to happen again, keep the "shock" levels up for a few days and brush to get rid of it. Also, heed my warnings and never let your PH dip below 7.0 in the future.

Dave

[gumbeaux71]

Thanks Dave and everyone else.
You are right that no one on this site recommended lowering my PH so drastically. The "helpful" woman at the pool store did. LOL. I've actually been lurking around this site (previously under gumbogal) for a long time. I use the BBB system except, I got lazy this season. I need help from hubby to take off the pool cover for testing/maintenance and I was lazy about asking to him to do it. (He totally would have had I just *asked*. :( )

So, when we opened the pool and saw the staining, I asked at the local pool store about it because I wanted to get right on it and couldn't remember my password here to ask for advice! The lady there had me convinced it was metal, but I knew something had to be up when the Vit. C didn't work. ARGH.

Oh, and BTW, I get nada when I test using the DPD test (I have the PS233 kit). I only applied one dose of YellowOut, but I guess it's still eating my chlorine. I'm going to follow your advice of keeping the Cl up and brushing. Thanks! :D

[gumbeaux71]

Waterbear,
Thanks for the link to Ben's post. I actually read that many moons ago when I first became a pool owner, but before I knew just what "adventures in poolcare" awaited me!

Makes a lot of sense now!

[smallpooldad]

David,

I cannot speak for vinyl liners only gunite/plaster.

Yes for my 9000 gal pool here in Honolulu I first got rid of all the chlorine. Then lowered, using Ben's calculator, the ph to 6 -6.2. Then added 1 quart of Algaeside 60 as a a preventative measure as we have lots of sun and I did not want an algae bloom

This was immediately followed by 1lb of ascorbic acid POWDER (not the crystals as these are non-acid and would not work). Then added 3 quarts of metal out to take the metal out of solution. Ran it through the filter for 48 hours non-stop adding 1/3 lb of DE to trap smaller particles. The 300 lb sand filter clogged-up pretty good after 24 hours so I back washed it for 1 minute only; leaving much of the remaining DE in the filter. At 48 hours it was pretty clogged so I backwashed it until it was clean.

The pool had never been treated for 10 years and as Hawaii's soil is mostly volcanic, "Red Dirt" as it is known, it contains a good amount of Ferric Oxide or if you like rust. The pool prior to this treament was dark brown to orange in other words terrible. After the treatment it looked nearly like new. Some light spots remain which I suppose are due to the stain being deeply imbedded in the plaster. No damage whatsover was done to the pool, pump, or filter. I did bypass the heater. I drained the entire pool to flush out the remaining iron in solution.

The ph of ascorbic acid I believe is 6.0 (MSDS sheet information) so I would guess no matter what ph you start with below 7.6 it would in any event take it down to 6.0 depending on the amount of ascorbic acid powder. So adding 6.0 to 6.0 would it really make any difference in few minutes time? I measured the acidity using a fish tank test kit about $10 which measures down to 6.0. Mine got as low as 6.2.

It might be that as I had so much ferric oxide in the pool this is why it did no damage, but I did it once again to see if I could get rid of the remaining stains. It helped a little but again no damage was done to the pool. I know that when the pool was built we had one of the best concrete persons in the state do the building. I got lucky that might be why the walls held up so well. The second time I did not drain it.

Finally being a little nuts and reading a white paper on agriculture put out by about seven state universities it suggested using Sulfuric acid to precipitate out iron versus ascorbic, in irrigation systems, which puts it into solution and therefore harder to remove unless you drain. So I followed their instructions and lowered the ph to 5.0. It quickly rose after 24 hours to 7. Did it help initially not a lot, but two days later it seems to have really worked wonders on those faint stains. I did use 1 quart of metal out, it only affected the alkalinity by lowering it from 90 to 60. No effect on calcium, CL or CYA, and contrary to popular believe the TDS was hardly affected. And certainly no damage to the pool at all, in fact to the contrary it looks better than ever.

I am no expert but this is my experience. Ignorance can be a blessing. Not having completely understood what I read on this web site may have been a blessing in disguise. Had I fully understood things may not have worked out so well. Many years ago when I was young I was selling my first little home in an enviroment of 15-17% mortgage rates. I assumed it was the realtors duty to show my home close to 24/7 not knowing this was not how it was done I harrased her and her boss constantly. The house sold at the asking price three days later. Some years later I had a realtor friend who explained to me how things worked. My next home took 1 1/2 years. I was carrying two mortgages, I wished I had remained ignorant.

I love this website and have learnt a tremendous amount especially from Mbar (Marie) and I enjoy the constant difference of opinions as it makes me think that much harder. But I do think you may indeed be correct with some concrete pools where the quality of the mix is in question. I tried to tell a good friend of mine that when pouring foundations for his home he should have a concrete engineer specify the mix and be on site to test it during the pour. He did neither, his foundations cracked, they had to be removed and re-poured, this cost him $60,000 plus.

[ksturge]

I have the same problem - yellow stains at the bottom of my vinyl liner from leaves that sat at the bottom all winter. After reading the previous threads, I'm not sure that an answer has been posted. I have not added any yellow out - my water is perfect, but I can't get the stains out. Any suggestions on how to get rid of the leaf stains?

[smallpooldad]

I believe that before this forum lost all of its messages that a post was made that stated shocking it at very high levels with liquid chlorine and keeping it at that high sustained level for 48 to 72 hours would go a long way to removing these stains. They are caused by the tannin in leaves and the chlorine helps to dissolve the tannin.

I have done the same and it did help, although some minor stains do still remain. They are slowly (three months) going away as I keep it on the higher end of Ben's CYA calculator for the normal chlorination measure. I have many leaves falling into my pool.

Hope this helps.

Good Luck

[ksturge]

Thanks, that advice seems to be working. Lighter and lighter every day.