Ascorbic versus Oxalic Acid / CYA pre-dilution

[mbar]

How is your pool doing now? What was your ph when you refilled your pool? I have been trying to figure out stains for a while now - and am interested in results from those of us who do battle! This is my opinion on what works. I have only used ascorbic acid, so I can't give you any info on the Oxalic. First let me say that if you use pucks in your feeder, your cya will go up from the stabilizer in the pucks. The reason your chlorine was being used up is that the stain treatment uses chlorine - that is why they tell you to lower your chlorine before doing the treatment - otherwise you are only using up the treatment with the chlorine that is already there. When trying to get rid of the stains, you should always have a sequestering agent in the water too, something like metal free or sequasol. The stain treatment is lifting the stain from the surface of the pool and puting the metal back into solution. You need the sequestering agent to bind onto the metal so that the metal will be filtered out. I always keep my filter running 24/7 when doing a stain treatment. I use polyquat as a preventative till I can get my chlorine back up. Your chlorine will be used up while it is filtering out the metals - you may even get cloudy water if there is a lot of metal in solution that has to be filtered out. Keep your ph no higher then 7.2. You will notice that doing the treatment will also bring down the ph. It isn't necessary to drain your water. You just want to make sure that there is enough sequestering agent to keep the metals suspended until they are filtered out. It is a good idea to put a chlorine puck in the skimmer so that the stain will come off on the filter. Raise the chlorine in the pool slowly - when you notice that the chlorine is lasting, then you can start to bring it up to (with a cya of 25 - 30, you only need your chlorine at 2 to 3. Do not shock for at least 2 weeks, keeping the filter running 24/7. If you see stain starting to come back, lower your ph, back to 6.8, add sequestering agent and see if they lighten up. It means that there is still some metal in the pool. Keep the filter running and keep a chlorine puck in the skimmer. Low cya means you don't need high chlorine. There is no need to shock if there is no algae. Keeping up with the water is the best bet. Keep your ph at about 7.4 - higher ph combined with high chlorine will make any metals stain the pool. I hope this helps you, if you have any questions feel free to ask. You can look in the metals forum for more discussions on stains. Welcome to the forum!

[smallpooldad]

Thank you for your reply.

The pool is much better although there are some stains reappearing. The pool water was 7.8 when I refilled it and I am now maintaining it at 7.5, which seems to just stay there as long as the alkalinity is maintained at 100 not allowing for the CYA adjustment. The CYA is now 33 is this too high?

The cl is between 4 and 6 is this too high?

I did add metal out and a polyquat when I refilled.

Next time I'll try holding it 7.2 for two weeks and putting pucks in the skimmer

[mbar]

Your cya is good. Your chlorine level is fine - you can keep it closer to 4 - here is the best guess 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

As you can see with a cya of around 30 you can keep it on the low side around 3-4. I would run my ph around 7.2 to 7.4. You may want to add some more metal out, if the stains are coming back you don't have the metal in the water staying in solution. - and run your pump 24/7 for a couple of more days. Don't shock the pool for at least 2 weeks, I only shock if I have combined chlorine. Remember the pucks will add cya, and also bring down your ph because they are acidic, so I would keep the puck in the skimmer for a couple of days, if you have either a DE or sand filter.

[duraleigh]

Hi, Paul,

I can't comment on the stain issue...wish I knew more.

Your CYA of 33 (is that a pool store reading?) and Cl of 4-6ppm are just fine. Your CYA will slowly rise if you continue using pucks. You might want to think about an alternate source of Cl.

Dave S.

[smallpooldad]

Once again thank you to both of you.

I will drop the ph to 7.2 and put a puck in the basket. I will also add more metal out and use liquid chlorine to adjust cl in the future.