Can I use summer rain to lower CYA?

[techieprof]

I live in central Florida. Our average annual rainfall is 52", and we're in the rainy season. I haven't yet used the pool water dilution method to find out how much over 100 my CYA is (updated with estimate by this method, below). I'm kind of afraid to learn. I've just taken over pool chemistry for my family, and am switching to liquid chlorine, but I need to lower the CYA that has been added with the dichlor and trichlor in use until now. I want to minimize cost, and my current thought is to drain the pool to just above the skimmer and let it refill with rain repeatedly to lower CYA gradually. Last year we had 18" of rain in July and another 18" in August. Within a year, we'll be resurfacing the pool, and we can get a one time break on water cost when refilling. I don't want to use that up yet. The pool is cloudy, but there's no visible algae on the surface. I know I need to keep the FC up with the CYA so high. Is this drain a few inches and refill with rain plan a reasonable strategy?

TA - 50
CH - 270
FC - 1
CC - 0
pH - 6.8
CYA - >100

Based on these readings, I am adding soda ash, baking soda, and liquid chlorine. (Our old pH Up, stored outside, seems to have lost its potency. I am now adding washing soda, which is stored inside. It's also old, but still I am hoping to see some increases in pH and TA.)

Thanks for reading and sharing your expertise!

 

[tim5055]

Welcome to the TFP pool! :splash:

As long as you are actually pumping water out of the pool it will work. If you are just using the rainwater to make up for evaporation it won't work.

I took over my pool with a CYA of about 250 (CYA tests above 100 are just a guess, not very specific contrary to what the pool store says). With a CYA of 250 I had to keep my chlorine level at around 20 just to keep algae away.

I rigged up a system to harvest rainwater from my roof gutter to do exactly what you propose. Every time it rained I would pump water out of the pool and let the rain refill it.

Have fun in the land of Publix!

 

[techieprof]

Thanks so much! I pumped 3" out of a full pool yesterday without benefit of a pipe clamp for the drain hose, which was all my grip could take. Today I bought another pipe clamp, and we officially got 1.5" of rain but the pool was full again and I pumped out about 4.5". I don't like to get it much lower than that since evaporation could leave me having to add water, but more rain is expected tomorrow. Thanks again for the encouragement, and long live Publix!

 

[tim5055]

long live Publix!

My stock depends on it!

 

[elight]

I also live in Central Florida. Although I rarely use tabs, I think that probably you could get away with it here to some extent in the summer without horrible effects due to the amount of rainfall. I find myself adding CYA multiple times per year just to keep it at 30.

 

[techieprof]

I long to need to add CYA! I think mine might be around 270. With rainwater diverted to the pool when it rains, I can take out 3+" many days without adding water beyond the rain. I'd love if it were just on the scale by the end of July.

 

[techieprof]

In case anyone is reading this with the same question, after not quite two weeks of rainy season, directing extra rainwater into the pool beyond what falls on it and draining after every decent rain, I am now estimating CYA at 130. I realize most people would not celebrate CYA so high, but this is down from an estimate of 270. The water is clearer, and more rain is on the way. Thank you God for the rain!

 

[tim5055]

In case anyone is reading this with the same question, after not quite two weeks of rainy season, directing extra rainwater into the pool beyond what falls on it and draining after every decent rain, I am now estimating CYA at 130. I realize most people would not celebrate CYA so high, but this is down from an estimate of 270. The water is clearer, and more rain is on the way. Thank you God for the rain!

Any CYA reading above 100 is as much guess as it is accurate. Your "270" could have easily been 300 or it could have been 230. Your current 130 is also still more of a range, I'd say 110 - 150. Even once you get on scale there is a 5 point or so fudge factor.

The good thing is you are moving in the right direction. It took me a year to make the progress you have made. Good job!!

 

[techieprof]

I saw that, thanks. I am feeling giddy that I may be on the scale soon! Longing for the 80 to do a SLAM.

 

[techieprof]

Just wanted to provide an update for any future readers of this thread. During a central Florida summer, when we get lots and lots of rain, and with directing rain water to the pool beyond what would fall on it naturally, it took a month and a half for the estimated CYA to fall from 270ish to between 90 and 100. I was using old DPD test powder and getting falsely low FC readings for a time, so I was adding too much liquid chlorine until I replaced the DPD test powder. While it was unintentional, I essentially did a SLAM at high CYA. The pool is now clear with no CC. On rainy days it sometimes tests at 0.5 CC. The lowest I have let the FC fall to is 11.5, and I am currently dosing with liquid chlorine to raise to 13+ each evening. I realize I didn't get here by the recommended path, and it was expensive to add so much liquid chlorine for awhile, but I am relieved to have the pool in good shape except for the high CYA, which I am continuing to reduce by draining after rain. I hope I didn't do damage with the high liquid chlorine dosing.

 

[ka8yiu]

I am always having to add CYA because of needing to pump out rain water through the summer. I had to pump out about 3 inches the last two days. I just got finished hanging a sock and adding some calcium from the recent dilution.

 

[techieprof]

I may be there with you eventually, ka8yiu. I was happy to read a CYA test of 55 last night. So much progress in just under three months, and with rain water instead of a huge water bill! I'm hoping I can learn to manage CYA with dichlor and trichlor when I get to that point since I have some of each on hand still.

 

[Dirk]

Nice job on the CYA reduction! I tried a little rain water replacement experiment once. It definitely works if you stay on top of it. But it doesn't rain here anymore in CA...

Don't forget you're reducing your CH level, too, which was already on the low side. Have you been testing that? Adjusting that? Feel like posting a full suite of test results?

 

[MBergen]

Hi All, I am replying to this thread instead of starting a new one with some what the same questions. Live in the northeast and it has rained continuously here all summer, I had incredibly high CYA at the beginning of the year due to previous years of using tri-chlor tabs, I drained and drained and drained until i finally got the CYA down to the 50 range using the guesstimate strips since that my pool has overflowed with each and every rain we have gotten over the summer too many times to count. I finally got a Taylor 2006C kit and ran 2 test both coming in at the 58 to 60 CYA
my ph is high as well over 8, How do you tell exactly once over 8? acid demand test took 3 drops to reduce to 7.4
So my question is with all the rain I have gotten and pool overflowing constantly wouldn't it still dilute the CYA with out draining? And is it the rain that is driving my ph up or is that a side effect from only using LC? I have used a gallon of muratic acid this year lowering my ph and pool math tells me I will need to add another quart or so. It is time to close here so I will drain some but not a third.
Todays readings:
FC - 5
CC - 0
Ph - 8.5?
TA - 120
CYA - 60
CH - 90

 

[Dirk]

The rain physically roiling the water, causing aeration, can drive up pH.

I don't use acid demand testing, so I can't speak to that. When I get to pH8, and don't know how much higher it might be, I just use 8 in Pool Math and dose accordingly. Once that gets mixed in (30-60 minutes later), I repeat the pH test. If it's below 8 at that point, I know where I am. If not, I'd repeat that process until I get a readable result. I've never actually had to do it more than once.

Here's what might be happening regarding the recent rain and CYA. All pool water has salt in it, accumulated from chlorine, acid, humans, fill water, etc. When it rains, that is fresh water, and it will float on top of the salt water (because salt water is more dense). When your pool overflows, what's draining off is the rain water, and not much of the pool water. It's not a completely separate layer, there would be some mixing, but not as much as you think. One solution, if you want the rain to help with CYA reduction, is to run your pump while it's raining, to better mix in the rain water with the pool water. Or go back to draining before a rain. When you do it that way, the CYA leaves with the initial drain, the rain doesn't drain out, and so mixes in with the next pump run. Did that make sense?

 

[MBergen]

Thanks, I have run my pump 12 daily up until 2 weeks ago I cut it back to 8 so it has run during many of the rains. And as I said previously I was using the guesstimate strips to check cya, I had a small test kit for ph and fc and ta. I guess it's possible the rain has bubbled enough to aerate.
But one thing is a sure definite, since switching to just LC my pool has been incredibly easy to maintain, even with daily dosing in the rain.
I am seriously thinking of switching to SWG to further the ease.

 

[Dirk]

Thanks, I have run my pump 12 daily up until 2 weeks ago I cut it back to 8 so it has run during many of the rains. And as I said previously I was using the guesstimate strips to check cya, I had a small test kit for ph and fc and ta. I guess it's possible the rain has bubbled enough to aerate.
But one thing is a sure definite, since switching to just LC my pool has been incredibly easy to maintain, even with daily dosing in the rain.
I am seriously thinking of switching to SWG to further the ease.

Now yer talkin' TFP!!

 

[ka8yiu]

I'm hoping I can learn to manage CYA with dichlor and trichlor when I get to that point since I have some of each on hand still.

I was out of town for five nights in August, and my CYA had been dropping towards 30 as the trip approached. So, I was able to use some tablets to help maintain my chlorine while gone, and raise the CYA back up. So, knowing your levels and you can do that. Good job using the rain water!

 

[techieprof]

Nice job on the CYA reduction!

Thank you! I am very happy with the results! So much nicer than paying for gobs of water!

But it doesn't rain here anymore in CA...

Oh my!

Don't forget you're reducing your CH level, too, which was already on the low side. Have you been testing that? Adjusting that? Feel like posting a full suite of test results?

Yes, I have raised CH. I enjoyed showing my 12 year old the exothermic reaction. =) The pool needs it again now.

CH 230
CYA 40 (no longer intentionally lowering)
TA 100
pH 7.5
FC 7
CC 0

 

[Dirk]

Looking good. Continue to work on CH and TA... TA will likely fix itself, but it's a little high right now. It's fine if you're not battling with your pH level. CH is still a little low.