Stain Experts Question!

[riverheightsnancy]

Hello all, I have been reading this and two other similar forums and have received valuable information (thank you!) on how to remove iron stains out of my very old Sylvan pool. We bought the house last year and the pool has been neglected by the pool guys and the prior owners. Needless to say, it was very heavily stained with iron. I followed the stain ascorbic acid technique carefully and it came out beautiful. I really could not get over how white. (it did need 12 pounds of vitamin C though). I added the Poly Quat 60 and Jack's Magic pink stuff as the technique suggested. I started to raise the chlorine slowly and watched my levels carefully. (I have a Taylor's K-2005) I have an Hayward inline chlorinator with trichlor pucks, which I have been trying not to use.

About 2 weeks after the treatment we had some rain, I get a lot of pine needles and acorns in my pool (we live in a woody area) and I must have let the chlorine slip overnight. I started to see cloudiness and assumed that I was getting an Algae bloom. I used several bottles of bleach and added another quart of the poly quat and an entire bottle of Pink Stuff just to bypass the stains from coming back. I have been unable to get the cloudiness to go away and it has been over a week. We got a huge storm two nights ago, I spent 4 hours cleaning the pool yesterday and taking out the organic matter, vaccuming, etc... The pool was visibly cloudy, with a very slight green tinge. I shocked with two bottles of clorox. Today it is better, just a little cloudy.


Numbers before the Algae bloom:
FC 2.5 TC 2.5 CC 0
PH 7.4 CH 210 Alk 130 CYA 60

Today
FC 15 TC 15 CC 0
PH 7.2 ALK 110 CH 200 CYA 50

Here are the advanced questions:

1) I am starting to see light staining again in the deep end. It is very light on the bottom of the deep end. I put in 2 quarts of the Pink Stuff immediately and had been using a maintenance dose as suggested. I have been adding PolyQuat 60 as a maintenance too. We got some rain and organic matter in the pool. What would cause the new staining? The Algae, the chlorine level? I started using the in-line chlorinator again, as we are going away on vaca for a few days and I wanted the pool to not go green while away. Is there any evidence that trichlor causes or contributes to iron staining? What should I do to prevent this? I am so disappointed, because the pool was looking very good for how old it is and it is in need of a new resurfacing of the paint. (some has come off and you can see the concrete-could this issue be causing the problem?)

2) How should one handle an algae bloom if one has a staining problem like iron? (I know, don't get one, but if you do, how should one handle it if staining is a problem?) I added the PolyQuat immediately when I saw the cloudiness, it didn't seem to help. Is it common to get an algae bloom after rain? Should one be proactive with the bleach when it rains?

3) Does Poly Quat reduce chlorine, does one need to add chlorine after a Poly dose?

4) Does the surface of the pool, in other words, how old or porous, affect this staining process or how fast the stains will come back? (thats what the hubby thinks)

5) Slightly off topic, but...Would love to know what the procedure is for closing the pool for minimizing the stains upon re-open.

Proof of how well the ascorbic acid treatment works!
Photos: Intake before ascorbic acid treatment.

Side wall during treatment/left side down, right not.

10 Minutes after treatment.

30 Minutes after.

My pool!

Original Sylvan brass step insert, its cute!

Thanks in advance.

 

[JasonLion]

Welcome to TFP!

1) Either or both of increasing the chlorine level and increasing the PH combined with slightly too little sequesterant in the water can cause the stain to start to return. Generally by adding more sequesterant as soon as you start to see staining return you can get things back under control. Sometime you also need to lower the PH a little.

I believe that the maintinance dose of sequesterant is designed for up to 1 ppm of metals in the water. If your metals level is higher you will need to use a larger maintinace dose.

2) If your sequesterant level is good then the only stain related thing to watch out for with algae is to not to let the PH go way way up during shocking. Since the PH test can read incorrectly when FC is high mostly this just means checking that PH is on the low side before starting to shock.

If you expect a major rain it is a good idea to add extra chlorine in advance so it doesn't get too low at any point.

PolyQuat is much better at preventing algae in the first place than it is at fighting algae once the algae has gotten started.

3) Yes, PolyQuat consumes a fair bit of chlorine. You need to add more to compensate.

4) The surface of the pool won't have a significant affect on the staining though you might see some minor variations from place to place based on the plaster surface quality. Water chemistry, and how it varies from one spot in the pool to another, has a much larger effect than the shape the plaster is in.

5) Add extra sequesterant.

 

[mbar]

I also noticed that your alkalinity dropped 20ppms, and your calcium dropped 10ppms, ph also dropped. You probably had some carbonate dropping out of the water, makeing the water cloudy too. With the algacide and all the sequestering agent, along with the ascorbic acid treatment not too long ago, the water seems to have reacted. I don't know why it happens, but I have seen it happen in pools that have gotten algae right after the ascorbic acid treatment. You got algae by letting the chlorine drop below 6, with a cya of 50, according to Chemgeeks chart, you need a target chlorine level of 5.7, with a minimum of 3.7. Especially with all the chems in the water, you should be very careful right after the ascorbic acid treatment to watch the chlorine level. Algaecide, and the sequestering agent are consumed by chlorine, so as you can see the chlorine demand will be a little higher after the treatment.

This said, I would take the chlorine level up to 20 (which according to chem geeks chart is the shock level) and keep it there until the chlorine holds overnight. Keep the filter running 24/7, and keep the ph low. You may see a little milky substance in the water, and you may see what looks like white powder on the bottom of the pool. You can vacuum this to waste, and put a skimmer sock on the skimmer to catch the really fine particles. It will take a couple of days to clear the water up. You may notice that your alk will go down a little more too, don't worry about it. You can use the chlorine tabs while you are away. I don't think it will make a difference with the stains. You may get a little staining, but when the water is clear and the chlorine level drops back down to normal, I think the stains will lighten with the low ph. If they don't, add a little more sequestering agent and they should lighten up.

As far as how to close so you don't have stains when you open - The stains usually disappear on their own over the winter. It is when you open that is important. Just make sure you put in sequestering agent before you add the chlorine, and keep your ph low to start out while shocking the pool. Hope this helps - just ask if you have any other questions.