CYA => Ammonia - getting FC up

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M

mvrisch

0
Jun 25, 2008
15
Hi all-

Seems like the time of year when I need to lean on everyone's expertise. We just opened our pool, and we had the CYA to Ammonia conversion that others have written about. My numbers yesterday were:

21500 Gal. outdoor SWG pool
0 FC
4 TC/CC
0 CYA
6ish ppm Ammonia

Other chemicals were fine, I added maybe a couple pounds of CYA - not enough to do anything.

So, over the course of an hour, I added 24 96oz jugs of bleach, 3 182 oz jugs of bleach today, on top of 1 182 oz jug I added yesterday plus my SWG cranking away at 100% all last night.

Not counting yesterday and the SWG, the pool calculator says that's 63 ppm.

A couple hours later, I measured, and found this:

0 FC
0 TC/CC
10 (maybe) CYA
0ish Ammonia (as far as I can tell - I'm between fresh and saltwater, so the default color matches neither card - however, the color never changed from when I put the drops in).

I cranked the SWG back to 100% and added a few more pounds of CYA (still dissolving).

Am I on the right track? I read about others getting their FC to stay up over a period of time - with 0 CYA, is "up" 1 FC? Is the chlorine burning off quickly, or is it still eating something in the pool?

Any tips on where to go from here (other than being patient) are appreciated.

Regards,
Michael Risch
 
Keep adding the chlorine. That's the only solution.

One thing you can do to help is add it only in the evening so (because you have so little CYA) you will get maximum use of your chlorine.

Whether it's eliminating algae, other organics, or the ammonia doesn't really matter......they have to be gotten rid of. Gallons and Gallons of bleach (but not without measuring) is your only path to success.

I would also turn down your SWG. It is really not capable of helping you obtain the high levels of chlorine that you need and you are shortening the cell life.

This "shocking" process is best done with chlorine only....save the SWG to maintain your FC when you get done shocking.

Each gallon of bleach you put in there is helping....you simply must keep going until you can measure some FC that is staying in your pool.
 
The reaction with ammonia, with Combined Chlorine (monochloramine) and with other intermediates that don't register on the test is relatively fast, especially without CYA in the water. If you wanted to know how much chlorine it will take before it starts to register, you can do a bucket test, scaled appropriately. Or you can just keep at it with chlorine since there's not much else you can do other than water replacement.

In my situation summarized here, there was 0.8 ppm CC and 2 ppm ammonia so theoretically that should have taken around 15 ppm FC to clear, but actually took 56 ppm FC.

In your case with 4 CC and 6 ammonia, that theoretically takes at least 44 ppm FC to clear, but you may have less intermediates than I had since I sort of caught my CYA-->ammonia conversion "in process". A reasonable estimate could be had if you knew your CYA level when the pool was closed. In that case, it roughly takes 2.5 times the CYA level in FC assuming it all gets converted to ammonia or intermediate products.

Richard
 
2.5 times CYA? I'm going to need some more bleach! I had like 70 CYA for the SWG!

I'm going to see if there is any FC this morning (last year something like this happened, and I was really discouraged, and then all of a sudden I had FC). If it is low, I'm going to go buy more bleach, I guess.
 
On the bucket test, what am I checking every 1/8 tsp? FC? How long do I wait? I've read several posts on the bucket test, but that part has not been clear to me.

In any event, I just added 8 more 182 oz jugs (33ppm). I did a test in an area that I did not pour the bleach half an hour later, and the strip turned dark purple - way over 10. I'm hoping it wasn't just a bleach spot.

I also added more CYA today - the batch from yesterday is fully dissolved.

We'll see what it looks like in 3 hours and in the morning!

Thanks all for your help.
 
You want to make sure the pump is running while you are adding bleach, and for at least an hour afterwards. If you do that, it shouldn't matter too much where you take a water sample for testing.

There is no need to do a bucket test except to get an estimate of how much more chlorine you are going to need. If you do a bucket test, you should mix throughly after each chemical addition and then give it 30 minutes, or more, to react before testing and adding more chlorine.
 
Our pump runs 24 hours a day, and both our filter and our pump are oversized - previous owner's doing. I'll need to get a timer to save on electricity at some point.

2.5 hours later, and still way up on the FC (dark purple on my strip). CYA appears to be up. I think I am in the clear. I turned the SWG down to 10% (normally runs at 30%). I'll do some detailed measurements tomorrow when some of the FC has burned off.
 

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2-3 days, with the SWG off.

If you haven't already done so, I highly recommend that you order a good test kit, and stop using the strips, they are very innacurate. You can read about the test kits recommended on this forum in Pool School.
 
Thanks - I have a good test kit - I used it for the CYA. It's not cheap, though, especially since I just spent $60 on bleach - so "dark purple" is good enough for me until I'm closer to a chlorine level that I need!
 
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