Algae stains

[dford8583]

I have a lined pool. I have been keeping up with chemicals and feel decent with my balance. Ph has hovered around 7-8 all winter. I have been checking chlorine and dosing to 7.0 ppm. No combined chlorine has been registered but free chlorine has gotten down to 0.6 ppm at its lowest.
I notice there are what appears to be algae stains on the liner at locations. I have shocked my pool to bring to 13 ppm as recommended by the trouble free pool app. I was expecting to see the stains clear up but after a day the stains are still there. I am thinking I will scrub this evening and checking in the morning. Any thoughts on what is going on here?

 

[Texas Splash]

Let's first confirm the type of stain. Try these two tests:
- Rub a vitamin c tablet across the stain for a few seconds - iron.
- Rub a chlorine tablet on the stain (keep moving) - organic

The only other item is copper and you shouldn't have that unless you added a copper-based product.

 

[dford8583]

Let's first confirm the type of stain. Try these two tests:
- Rub a vitamin c tablet across the stain for a few seconds - iron.
- Rub a chlorine tablet on the stain (keep moving) - organic

The only other item is copper and you shouldn't have that unless you added a copper-based product.

What kind of vitamin c tablets? I know that’s probably a silly question lol..

 

[mknauss]

What kind of vitamin c tablets?

Basic, cheap, Vitamin C tablets. Crush them up a bit after putting them in a sock.

I see a Nature 2 device in your signature. Do you use the mineral pack in that?

 

[dford8583]

Basic, cheap, Vitamin C tablets. Crush them up a bit after putting them in a sock.

I see a Nature 2 device in your signature. Do you use the mineral pack in that?

thanks for the insight.
yes you are correct on the nature 2 device. We bought this house Jan 2020 and the nature 2 did have the cart in there. I removed the cartridge using guidance on this site.
Is it possible that metals could show up as stains a year later?

Last night, I checked my cya level (30), scrubbed the pool, vacuumed, and dosed with cal hypo to bring fc to 13. Been running pump non stop. Checked fc this morning and it was sitting at like 11.5 ppm.

 

[mknauss]

Is it possible that metals could show up as stains a year later?

Not likely in your climate as you get rain and I suspect some overflow from your pool. Good job on removing the cartridge.

Last night, I checked my cya level (30), scrubbed the pool, vacuumed, and dosed with cal hypo to bring fc to 13. Been running pump non stop. Checked fc this morning and it was sitting at like 11.5 ppm.

Sounds good. Algae rarely leaves a 'stain'. It should brush off easily.

 

[dford8583]

Basic, cheap, Vitamin C tablets. Crush them up a bit after putting them in a sock.

I see a Nature 2 device in your signature. Do you use the mineral pack in that?

I have these chewable tablets. Are these ok?

 

[mknauss]

Sure.

I have these chewable tablets. Are these ok?

 

[dford8583]

Sure.

Awesome, I’ll see what those do.
also curious if some existing staining on steps is copper. What should I do to test for copper? Is dry acid appropriate for vinyl liner and steps?

 

[Newdude]

Hey Dford !! Quick question.... although you have been keeping up with the water chemistry all winter, have you been brushing too ? If not it’s probably just long overdue and normal after sitting. Aglae grows a biofilm over to protect itself and your winter pool chores probably weren’t as rigorous as your swim season ones so a little growth isn’t out of the question.

Now that you’re back in the swing of things it might fix itself. If not perform an Overnight Chlorine Loss Test to see if you need a mini SLAM Process to help it back to normal.

 

[mknauss]

What should I do to test for copper?

The same Vitamin C will turn the stain darker if copper.

To remove copper stains is much more involved, and less successful.

 

[dford8583]

Hey Dford !! Quick question.... although you have been keeping up with the water chemistry all winter, have you been brushing too ? If not it’s probably just long overdue and normal after sitting. Aglae grows a biofilm over to protect itself and your winter pool chores probably weren’t as rigorous as your swim season ones so a little growth isn’t out of the question.

Now that you’re back in the swing of things it might fix itself. If not perform an Overnight Chlorine Loss Test to see if you need a mini SLAM Process to help it back to normal.

Not as well as i could have in all honesty. I did an overnight test last night at 11 ppm fc. it remained the same when I checked before daylight. I think the pool is clean. I have scrubbed and vacuumed the last 2 nights and have run the pump non stop. The stains don’t appear to be improving. I have not been able to get the stains at the bottom of the pool to do spot testing. Any suggestions guys on how to get to a stain at the bottom. Water is still pretty cold to jump in rub chlorine tab and c tabs on the stain lol

 

[mknauss]

Put the vitamin C in a sock, crush them up a bit, and use your pool brush to the sock in place on the stain.

 

[Newdude]

. I did an overnight test last night at 11 ppm fc. it remained the same when I checked before daylight. I think the pool is clean. I have scrubbed and vacuumed the last 2 nights and have run the pump non stop. The stains don’t appear to be improving

Ok so you ruled out algae and they are stain-stains.

 

[dford8583]

I suppose so lol. We do have some trees in the yard and over winter there were leaves that fell in. Someone mentioned tannic acid or something like that from the tree leaves

 

[Texas Splash]

If you rule-out iron and copper, then they could be tannin stains from leaves, acorns, bark, etc. They may not contribute to an algae bloom, hence the stable FC levels overnight, but they could have transferred the tannin to the pool's surface. They can be a bit stubborn. An elevated FC level for a few days (maybe longer), coupled with consistent brushing should help.