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/showthr...=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