Looks like algae on vinyl liner but will not brush off!

cmyoch

Member
Jun 21, 2007
20
Hi everyone,
This is my first time to the forum. I found this site last night and I must say I've already learned a ton with regard to water chemistry. Here is my dilemma.
I opened my pool a month ago to a swamp. I managed to get the water crystal clear and the chemistry correct within a week or so of hard work. My liner is completely covered with stains that look like algae on the floor and walls. The stain is not completely solid and seems to be in the pattern of the water flow in my round pool. The center of the pool has about a 2-3 foot radius where the stain is lighter. I thought at first that when the water was circulating and killing the algae, some of it settled and stained the liner. I've pushed my chlorine level off the chart trying to knock it out that way. No luck. I contacted Bio-Labs and was told I had metal stains. $75 later after adding their "Stain Remover" product, no luck. The water is clear, the liner looks horrible. Anyone walking up to the pool thinks I have a algae problem. Everything I read regarding algae states that it can be brushed off. Not this stuff. I can scrape it off with my finger nail but at that rate, I'd never get it clean. I brush, brush, brush one spot and it lightens somewhat but not much. Also, I put the white ladder in later on and no stains on it all which leads me to believe the "swamp" had something to do with this. Can anyone help me? I'm embarrassed to have anyone over to enjoy our pool. :oops:
 

mbar

LifeTime Supporter
Apr 24, 2007
257
Ashland PA
You may have some dirt encapsulated scale. You will have to post a full set of numbers so we can better help you. Especially calcium, alkalinity and ph.
 

JohnT

Admin
Mod Squad
TFP Expert
Apr 4, 2007
9,610
SW Indiana
Welcome to the forum.

I saw a pool that had been left closed for a season that had serious scaling and then algae for a year, and looked and felt something like you describe. Essentially it had algae and leaf stained calcium deposits on the liner. The first step is a good set of test results. You really need pH, CH and TA plus you'll probably want to get a pool store to test for metal in the water as well. Organic stains usually respond to chlorine. Metal stains respond to acid. You can check the stains for metal yourself by rubbing a small area with a vitamin C tablet. This will lighten a metal stain pretty quickly.

You mention the light area in the center. Is the water deeper there? Makes me think maybe chlorine has settled there and bleached the stain.

Let us know what you find out.
 

cmyoch

Member
Jun 21, 2007
20
I did have my water tested initially and it showed no metal. I don't always trust their tests though because I always seem to be walking out of there with $100 worth of chemicals. I'll go today and purchase some Vitamin c tabs to test it though. Last night's test (with test strips) shown PH at 7.2, Alk at 120, and Stab at 150. I don't have a calcium test. is this a test that comes in a liquid test kit or do I have to have the pool supply store test it for me?

As for depth, the pool is the same level throughout. I wondered if the circular pattern of water flow gathered a higher concentration of chlorine at the center. If that can happen?

Also, I need to mention that at the opening of the pool this year, all levels (PH, Alk, Chlorine) except for CYA were practically nill. Stabilizer level was higher which still is.

Thanks for all your help!

Craig
 

Rangeball

Well-known member
May 25, 2007
785
Craig, generally test strips aren't reliable, and you'd be better off with the 6 way drop kit from Walmart, best off with the TFP 100 kit from Dave :)

If by everything but stabilizer being nil you mean they didn't register on your test strip, remeber a low PH can damage a vinyl liner. It's possible low PH somewhat etched your liner, making it more porous and allowing the algae a better footing to take hold in. I'm confident this is the issue with my Dad's pool.

If you CYA is really 150, you need to run a very high chlorine level to get killing activity. If your stains are from algae, as I suspect they are (my dad's pool was in a similar situation, and his staining is lightening over time now that we have his bleach up to match his CYA), you probably won't get anywhere until you address your FC ppm based on the best guess chart.
 

JohnT

Admin
Mod Squad
TFP Expert
Apr 4, 2007
9,610
SW Indiana
cmyoch said:
I did have my water tested initially and it showed no metal. I don't always trust their tests though because I always seem to be walking out of there with $100 worth of chemicals. I'll go today and purchase some Vitamin c tabs to test it though. Last night's test (with test strips) shown PH at 7.2, Alk at 120, and Stab at 150. I don't have a calcium test. is this a test that comes in a liquid test kit or do I have to have the pool supply store test it for me?
The calcium hardness test is available in all but the most basic liquid reagent test kits. You can probably trust the pool store to get close on it, but don't listen to their advice. They'll want you to increase it when you don't need to.

I have to wonder with that high CYA if you just aren't getting enough free chlorine to do the job.
 

Rob

Well-known member
May 23, 2007
165
I suppose this isn't a good time to admit that I have a policy of "if it doesn't scrub off with a brush, I'm not going to worry about it, since it's probably inert anyways"

:)
 

cmyoch

Member
Jun 21, 2007
20
Thanks guys for all the valuable advice. What is the difference between TC and FC? 2 weeks ago, I triple shocked and the chlorine level was off the chart (based on a test strip) I thought that would take care of it. Maybe I didn't have enough in. With CYA at 150, what ppm should I be at and for how long? I'm doing 2 things this weekend, taking a Vitamin c tab to the liner to test and going out to buy a liquid test kit.

I wish I would have joined this forum long ago!!
 

Rangeball

Well-known member
May 25, 2007
785
TC= total chlorine, all that is present in the water which includes used up combined chlorine (CC) and chlorine still free to sanitize, free chlorine (FC).

This is the chart-

Stabilizer . . . . . . Min. FC . . . . Max FC . . . 'Shock' FC
0 ppm . . . . ... . . 1 ppm . . . . . 3 ppm . . . . 10 ppm
10 - 20 ppm . .. . . 2 ppm . . . . . 5 ppm . . . . 12 ppm
30 - 50 ppm . .. . . 3 ppm . . . . . 6 ppm . . . . 15 ppm
60 - 90 ppm . . .. . 5 ppm . . . . . 10 ppm . . .. 20 ppm
100 - 200 ppm ... . 8 ppm . . . . . 15 ppm . . .. 25 ppm

At high stabilizer/CYA, you need to run a high level to get the sanitizing effectiveness as a much lower level of chlorine with no CYA at all.
 

waste

TFP Expert
LifeTime Supporter
Mar 29, 2007
4,160
Coastalish 'down easter'
Rangeball, not to be too anal, but the 'Best Guess Chart' is for outdoor pools only -- we wouldn't want some indoor pool owner 'overdosing' their pool :angel:

cmyoch, hang with us and we'll get you through this better than most pool stores, and at a fraction of the cost :wink:
 

cmyoch

Member
Jun 21, 2007
20
Definately sticking with you guys. I have a few cases of liquid shock. I'll start working to get it up there and see what happens. I'll push the 20-25 ppm range. Hopefully this will knock it out. Please keep your fingers crossed!
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,083
San Rafael, CA USA
Because CYA reduces chlorine's effectiveness, it is actually useful to have some CYA in an indoor pool. Otherwise, even 1-2 ppm FC in an indoor pool is MUCH more corrosive. 2 ppm FC with no CYA is equivalent to 20.5 ppm FC with 30 ppm CYA and is higher than even the shock level we recommend for yellow/mustard algae, but is there ALL THE TIME. My wife's swimsuits degrade over a single winter of use in the indoor pool at our local community center with 2 ppm FC average (I finally got around to measuring it) with no CYA while in our own pool over the summer with 3-4 ppm FC and 30 ppm CYA there is no degradation whatsoever. Also, the higher disinfecting chlorine level in an indoor pool with no CYA most likely results in far higher concentrations of disinfection by-products (DPBs) since all reaction rates with 20 times the amount of disinfecting chlorine are around 20 times higher. Combine that with poor ventilation and no sunlight to break them down and it's an unhealthy situation. ALL incidents of asthma and respiratory problems with competitive swimmers and small children have been with pools with no CYA (indoor pools).

I've contacted some organizations that deal with competitive swimming (coaches associations, etc.) but they are all told by their pool operators from chemical manufacturers that CYA doesn't matter with regard to sanitation or preventing algae -- only FC levels matter -- and that CYA is not needed in indoor pools because there is no sunlight. So who are they gonna believe -- me, or the manufacturers?

Richard
 

cmyoch

Member
Jun 21, 2007
20
Okay guys, I was told to do one of two tests to determine what kind of stain I have. I set a chlorine tab on the stain and it didn't budge. I then set a Vitamin C tablet on it and it went away almost immediately! So this is supposedly a metal stain, not a organic stain. Any thoughts now on how to treat this without breaking the bank?? I have a 25 ft round pool, 48 in deep which I believe is 15,000 gallons. Any advice would be greatly appreciated.

I feel a sense of relief now definately knowing what kind of problem I now have!

Craig
 

The Mermaid Queen

TFP Expert
LifeTime Supporter
Mar 28, 2007
2,522
Northern KY
Mbar is our resident stain expert... she will be along to help you out!

Is your water 48", or your wall? If it is the wall, your pool volume is 12900. Also I have never heard of a 25' round... 24 is the closest...
24'x3.5' (water depth) = 11900
24'x4' = 13600
 

cmyoch

Member
Jun 21, 2007
20
I've never measured the pool. The prior owner said 25 foot. It was installed in the mid 1980's. Would there have been odd sizes then? I can make a point to measure and post the accurate measurement later.
 

The Mermaid Queen

TFP Expert
LifeTime Supporter
Mar 28, 2007
2,522
Northern KY
well, considering you should always go a bit light on the chems, because you can always add more, a thousand gallons or so won't make that much difference. But if you are talking 20% smaller, that could be trouble.

I would measure it, then you can use the tool in either the BleachCalc or Jason's Pool Calculator (links found in my signature) to calculate a more exact volume. For your depth measurement, use the depth of the water, not the height of the wall. (In case I didn't make that clear in my other post! :wink: )

ETA Here is MBar's stain treatment!
 

cmyoch

Member
Jun 21, 2007
20
13,000 gallons. I measured wall to wall and the width is 25 feet. Like I said before, the pool is at least 20 years old. Maybe they made 25 foot rounds then. BTW, I just had to explain to my wife why I was in the pool in the rain with a tape measure :oops: . Luckily, no lightning. Anyway, I read MBar's post on Absorbic Acid to remove stains. Is this a hardware store item or exclusively through a pool dealer?