CYA and Old Plaster

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T

TXNDallas

0
Jun 4, 2014
16
Murphy, TX
Pool Size
15000
I'm sure everyone's sick of hearing about CYA problems long since, so I will be brief:

I'm getting reverse osmosis performed today and have switched to sodium hypo for chlorination this past weekend (installed a Liquidator) from trichlor. I've been down this road with high CYA before and did a full water replacement on our 26.5k plaster pool/spa about 5 years ago. Anyway, CYA is again off the charts and I felt reverse osmosis was the way to go.

So, after the procedure is performed I'm very concerned about the initial load of CYA. The plaster in our pool is really old--at least 15 years, maybe original (22 years); tri-chlor has always been the primary chlorine source. That being said I read in threads on this forum years ago that CYA can leach out of old plaster over time. We're in Texas and have long hot summers. Has anyone found CYA to leach out of plaster in appreciable amounts? I'm trying to determine an initial amount to load the pool with CYA and I don't want to get back in the same boat I'm in now with off-the-charts stabilizer levels...thoughts?
 
That is quite unlikely to be an issue. Personally I don't believe that ever actually happens, but we have had some reports of things that are difficult to explain any other way. Even if it is real, it is quite rare.
 
I agree with JL and BP. I think that "hiding in the old plaster" idea got started because folks were not getting the CYA drop they expected after a partial drain.

Over time, I have come to the conclusion that probably was more a matter of simply not draining enough water or a calculation error on how much to drain.
 
Interestingly I just spoke to the owner of the company that is doing the RE on my pool (just started about 30 minutes ago). He said they observe this effect with some frequency; he suggested (without me asking) that I wait a week to measure the stabilizer level and add it following--the CYA level is currently 250. Not sure how I'm going to keep the FC in place in the interim but it's gotta be cheaper than risking another $700 RE process in short order. He did say the process might leave a 10-15PPM residual CYA level, he would test tomorrow to see, so I guess I'll be rolling with that. I'll let you know how it turns out...pools going to need calcium right off the bat so I will probably I use cal-hypo as an FC source the first week, hopefully won't be burning a ton of money on that one!

Another interesting thing, my phosphate level measured at 2000...I was shocked as I don't use any scale removers and there shouldn't be substantial runoff into the pool. I've never measured that (don't have a test kit that does phosphates), I'm stumped about the source.

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TXNDallas said:
Another interesting thing, my phosphate level measured at 2000...I was shocked as I don't use any scale removers and there shouldn't be substantial runoff into the pool. I've never measured that (don't have a test kit that does phosphates), I'm stumped about the source.
Click to expand...
It's probably in your fill water. Orthophosphate is sometimes used as a corrosion inhibitor in the water supply. I have 300-500 ppb phosphates in my fill water.

As Jason says, if you maintain a proper FC/CYA level then you shouldn't need to worry about the phosphate level.
 
Well processing is finished and they measured the CYA down at 30 and calcium at 140. Going to wait a couple of days and measure again. Those levels are probably good if they stay or don't creep much. TA's down to 50 so I will adjust in a few days after I'm confident of the readings.


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