Acid wash or re-surface

[william13]

If the ph, TA, FC/CYA are all in balance grab the kids and throw them in!

Nothing is in balance yet. I am in process of "non drain water exchange". But my empty rate (flow out) with the superior sump pump and a 100 foot 5/8 inch hose is 5 gallons a minute. To exchange 20,000 g it will take me 4000 minutes. 4000/1440 min in day. About 3 days.
I could cut the time as follows: I could safely drain 10,000 gallons and only have to deal with 10,000 remnant gallons so I could cut the exchange process to 1.5 days. After that, my flow in could be adjusted from 5 g minute to 10 g minute so It would take me 1000 minutes or 17 hours to refill pool to original level. So roughly I could save a whole day. I am also trying to determine if the whiteish areas on bottom of pool are delamination or calcium deposits

 

[JamesW]

Results: You can see remarkable results from images 1 and 2 going to image 3 and 4. But bottom of pool has a mottled look. The very light areas might be from further discoloration around a clean area or they may be another substance. I am not sure if I should do further analysis or repeat this whole process. As mentioned above I used more Vit C than recommended thinking there was so much iron it required more ascorbic.

It looks a lot better.

You might have some copper stains or maybe some scale.

Sulfamic acid might help if you want to go through the trouble of using that.

It depends on if you are happy enough with the results.

Note that any treatment might help and it might make things worse, so do at your own risk.

I would probably not do sulfamic at this point based on the results so far.

It looks pretty good.

 

[william13]

Thank you. Yes I need to hold myself back and appreciate the benefits achieved by the kind advice of TFP members. I will leave well enough alone.

 

[JamesW]

Couple of more questions:
1. assuming the stains are all iron, what stands in the way of perfection ie complete clearing of stain? Is a physical thing like Vitamin C can penetrate only so deep? Is it chemical in that it takes a certain amount of moles of Vit C to change the oxidative state of iron? Is it that the water becomes saturated with iron an no more can go into solution? Or other? Would going higher that 2.5 lbs per 10,000 gallons be of any benefit?

I think that some of the brown stains were silver, which is a more difficult metal to remove than iron.

Silver can come from algaecides or from ionizers.

 

[william13]

Silver!!!!! I am going to "MINE" my own business!!!!
BTW I am also going to drain some of the water through the "main drain" just 1-2 feet so I have less water to exchange. I would feel bad if when I balanced the pool again the iron came out of solution and I am not keen on chronic sequestrant additions.

 

[william13]

BTW something I never realized before. Do hydrostatic valves open "by themselves" ie automatically? If so why am I so nervous about pool popping?

 

[JamesW]

Do hydrostatic valves open "by themselves" ie automatically?

They should, but that is not a guarantee of the pool being safe.

The pool can still pop with the hydrostat open.

 

[Newdude]

+1. The spring jams or gets stuck and the valve doesn't open.

Or, the 2 inch(?) valve can only let so much water through at once and it may build faster than it drains into the pool.

 

[william13]

Thanks for the clarification.
I will not push the envelope.
I heard 6 inches below skimmers is safe and some say 2 feet.

 

[Newdude]

I heard 6 inches below skimmers is safe and some say 2 feet.

The pool water level must stay above the ground water level. The rest is pure speculation. Dig a test hole nearby. If it's dry, you can go drain at least that deep.

 

[william13]

The pool water level must stay above the ground water level. The rest is pure speculation. Dig a test hole nearby. If it's dry, you can go drain at least that deep.

TY but hard to dig around here, lots of coral!

 

[william13]

I took it a foot below the skimmer then lost nerve in the game of "chicky" and closed the main valve..

 

[william13]

Just a thought. Since my primary method here is the "no drain exhange' it would be best if I knew when iron levels were low.
I was thinking that I could use the salt level of the pool as a surragate marker for how much dilution took place. If the salt levels approach and approximate the house salt concentration as opposed to the 3700 beginning pool level then the process can be confortable terminated. Thoughts?

 

[Bperry]

Just a thought. Since my primary method here is the "no drain exhange' it would be best if I knew when iron levels were low.
I was thinking that I could use the salt level of the pool as a surragate marker for how much dilution took place. If the salt levels approach and approximate the house salt concentration as opposed to the 3700 beginning pool level then the process can be confortable terminated. Thoughts?

Salt test has a tolerance of +\- 200ppm so don’t expect any great accuracy trying to do it that way.

CYA at least has +/- 10-20ppm.

 

[william13]

Salt test has a tolerance of +\- 200ppm so don’t expect any great accuracy trying to do it that way.

CYA at least has +/- 10-20ppm.

Right!! (and thank you) But I started off with CYA of 20 ppm so any change would be within the tolerance. The salt starting level was 3700 so for example if I get "500" +- 200....it would still be valuable info in my specific case. What about calcium?

 

[Bperry]

Right!! (and thank you) But I started off with CYA of 20 ppm so any change would be within the tolerance. The salt starting level was 3700 so for example if I get "500" +- 200....it would still be valuable info in my specific case. What about calcium?

I think you’re expecting too much from it.

Your start salt level is 3700 +/- 200 so its 3700, 3500, or 3900. Then the ending level has the same issue so you are left with 800ppm of uncertainty from a starting value of 3700. I think you’re better off measuring how fast water is being pumped out and using that to estimate the percentage drained.

 

[william13]

I think you’re expecting too much from it.

Your start salt level is 3700 +/- 200 so its 3700, 3500, or 3900. Then the ending level has the same issue so you are left with 800ppm of uncertainty from a starting value of 3700. I think you’re better off measuring how fast water is being pumped out and using that to estimate the percentage drained. With the "no drain exchange method" which is what I am doing, one essentially dilutes the water. BTW its 5 gallon minute in and out. If the inital salt concentration is 3500-3900 and the final is 200 (which is 0-400)(which I have not done yet) then one could argue its 9x less or a 90% complete job. No?!

 

[Bperry]

I guess I’d be curious to see what the difference would be since you can record both?

 

[william13]

Right now the salt level is 800 or (600-1000). We are 48 hours into the 3 day process. Starting salt was 3800 or 3600-4000
pretend it was 3600 starting and pretend the current level is 1000. (worse case scenereo) We have reduced the salt by at least 66-75% with another day to go.

 

[Bperry]

Right now the salt level is 800 or (600-1000). We are 48 hours into the 3 day process. Starting salt was 3800 or 3600-4000
pretend it was 3600 starting and pretend the current level is 1000. (worse case scenereo) We have reduced the salt by at least 66-75% with another day to go.

Does your drainage gallons/minute match up with 66-75%? Just curious on how different the estimates come out.