Dose acid or chlorine?

[tmarcoux]

I have a SWG system that has very fast pH drift. I use poolmath nearly every day and add about 20oz of MA daily. I target a pH of 7.4-7.5, but 3 days of not adding MA and it's 7.8-8.2. The plaster is seeing the effect.

I just purchased a stenner pump, plumbed in the T and I'm ready to set it all up, when of course I started thinking.... Should I just dose bleach and deal with small amounts of acid manually, or continue with my plan of dosing acid?

I can always switch what I'm dosing (assuming a good cleaning).

Thoughts?

PH 7.6
TA 70
CYA 70
CA 275
FC/TC 5.0
Salt 2900
Borates 40

One last thought - the pool was originally filled with tap water, but the auto fill system fills with softened water (no other option). Could the soft water be contributing to the discoloration/scale?

 

[JasonLion]

You have several different things going on, which is confusing things a little.

Let's start with the PH drift. If you lower TA to 50 you should see much less PH drift. The only exception would be if you have fairly new plaster (which always has PH drift).

Nothing about your current numbers suggest you would get scaling. Could you describe your "discoloration/scale" in more detail? Perhaps a photo?

 

[tmarcoux]

I just tested again this morning and TA=60 - so I'm close there.

Here is the first picture.

View attachment 32257

- - - Updated - - -

I'm having difficulty with uploading the second picture. Something on this site or my browser is not working properly as I'm getting file size errors on 58k files...

Nonetheless, this is the landing and it's by far the worse part. But traces like this continue to grow. i had an acid wash done recently and it just comes back. I am not sure if it's buildup or leaching?

 

[JasonLion]

Try placing a vitamin c tablet on one of the stained areas and see if that has any effect.

 

[tmarcoux]

I'll do that. I have to get one first! But I'm curious as well.

FWIW - the stenner is all connected and working properly (dosing straight pool water right now).

 

[tmarcoux]

Ok. I went to the store and bought a small bottle of vitamin C tablets, and placed four of them on the step. Here's the results after an hour or so.

View attachment 32295

It appears as if it cleared some of it away - or at least there's a change. What does this indicate?

 

[Divin Dave]

It indicates the staining is due to metals in the water.

The acid in the vitamin c tab will lift metal stains caused by iron, copper, or whatever.

Teh first thing to do is try and determine where the metal came from and remedy that.
Most common sources are fill water which contains iron or an algaecide which most of them contain copper.

The metals may be able to be contained temporarily by using a metal sequestrant, but the ultimate remedy is to replace the water. If water replacement is elected, then do an acid wash to all of the plaster.

If replacing the water isnt elected, and the metals are sequestered, then the most common way to treat metal stainins is to do an ascorbic acid treatment. ascorbic acid is basically powereded vitamin c and can be gotten at health food stores, large pharmacies and the like.

Instructs for doing ascorbic acid treatment are in the How To's of pool school.

 

[tmarcoux]

The pool was drained, acid washed and refilled this spring. I was told it was scale from the solids in the water, not metals. However, as you can tell, it came back very quickly and my water has been balanced the entire time.

I've been reading a lot about AA treatments. My only concern at this point is will the Polquat 60 be sufficient to keep algae down in the texas 100 degree heat? Would it be better for me to add sequestering solution (Jacks Purple seems correct) to stop further staining, and treat what's there in Oct/Nov when the temperatures are down? Or will the polyquat 60 do an effective job of controlling everything for a couple of days?

 

[Divin Dave]

Hi,
Those are some good questions your are asking. Im not an expert with the poly 60. I live in texas too and would have the same concerns.

the sequestering should contain it and prevent it from getting any worse. If it were me, I know that I would wait until the temps cool down some.

Even if the staining does get a bit worse between now and whenever, the AA should take care of it.

Any idea where the metal may have came from? Any algecides used? or iron in your fill water?
As much as I hate to say it, testing for metals can usually be done at a pool store. As to the accuracy of any levels I would question, but it might confirm if its there or not.

Would not surprise me either if whoever did the start up put some algecide in it... ?

I saw your other post and the reply from Jason.... etc.