Question re Removing Metals from Filter Using Acid

[Mandy]

After doing a metal stain removal treatment, adding a sequesterant and re-balancing pool I am have a daily struggle with the stains reattaching to the pool surfaces. Each time this has happened the pH has been at 7.2 or below and my FC level has been at 5-6 with a CYA of 70. The instructions for the sequesterant say a maximum safe level is set at 1 Litre in 50000 litres. My initial dose was 270mls for our 27,000 litre pool and thereafter I have been adding 135mls almost daily to remove the continual staining.

I rang the company who supplies the product and was told I’m three quarters through the process and that the next step is to remove the metals from the water. I didn’t think this was possible using a chemical? Their advice was as follows:

Step 1: Place a clarifying gel block in skimmer (to attach to the metal particles once I re-dose to remove them off the walls again)

Step 2: Add another 270mls of sequester

Step 3: Run filter for 24 hours

Step 4: Change from filter to backwash and at the same time slowly pour 5 litres of acid into the skimmer to remove the metal from the filter and out through the backwash

Step 5: Recheck pH, it should not be affected but if it is then rebalance

Is this sound advice?

 

[JoyfulNoise]

Have you identified the metal stain? Is it iron or copper or ... ? Can you post up the names and manufacturers of all the chemicals they are requesting you add to the pool...I have not heard of a gel clarifier block so it would be good to see what that is.

 

[Mandy]

Hi Matt
Stains appear to be iron. I've treated them in the past. Old pool store tests used to show iron and copper levels however their tests no longer report these so I have no idea what their current levels are. Is it possible iron and/or copper could get into pool from very severe dust storms? We had several last year. I pre-filter our tap water prior to topping up pool. Please see photos attached. Klorman Industries manufacture the Pool Magic products and Lochlor the Multi Stain Remover.

 

[Mandy]

Just to follow-up on this. I did lots of reading and came to the conclusion adding acid to the skimmer is not a good idea.

I re-dosed my pool with the Aqua Treat 3 in 1 with three additions spread an hour apart. All stains on sides and steps that had re-occurred due to metals coming out of solution disappeared again. After 24 hours I backwashed then added a product called Lo-Chlor Filter Aid and Metal Remover as a slurry to my skimmer. I also added polyfill to my skimmer. After another 24 hours I backwashed again and re-treated with the Filter Aid and Metal Remover.

The pool and water currently look amazing.

I think the metals had come out of solution due to not adding enough Aqua Treat initially to fully sequester them.

I rang a rep from the company to confirm this and he agreed I should have added more. It would appear dosage instructions are just a guideline…….. He suggested once I complete using the Filter Aid and Metal Remover to add another 1 litre of Aqua Treat, wait 48 hours then backwash. Going forward he also suggested 1 litre four times a year to be used as a sequesterant.

I also let him know the “advice” I had been given regarding adding the acid into the skimmer and he told me not to do it and he would chase that up with the person concerned.

Since re-adding the Aqua Treat I have kept my pH between 7-7.1 and my FC between 3-3.5 but am feeling a little nervous as to what will happen when these increase. Time will tell…..

Sometime this week I will have my Iron and Copper levels checked at a different pool shop and hopefully they will read zero.