Reducing CYA, the Tarp method

Nitrock28

Bronze Supporter
Apr 19, 2017
16
Belgium
#1
Hi guys,

Recently I found out that my CYA level was way too high, somewhere between 250 and 300.

Having to replace around 80% of the water, doing it in one go would be too dangerous for my old vinyl liner, and multiple drain and refills would waste a lot of water.
Searching on the forum for people in my situation, I found that the tarp method would be the best alternative. I recently purchased a black solar cover (thick bubble wrap) which is too big for my pool, so it was perfect for this.

Here is my pool before the process (I will need to SLAM it after the CYA is back to standard levels),
https://www.dropbox.com/s/doc1cmibz6d23ki/20170429_075051.jpg?raw=1

I don't have a main drain, and my vacuum cap doesn't make a good seal, so I used this pump to drain the water in the skimmer, and then set the valve on my filter to waste. It is not ideal as a lot of air was sucked in the main pump through the skimmer, but in the end the pool drained successfully.
https://www.dropbox.com/s/rh68nwg1cxanvs3/20170429_075442.jpg?raw=1

Here is the new water filling the sheet, at first I was afraid that the bubble sheet would want to float up, but it worked very well. I think it even added a little stability, keeping the sides of the sheet out of the water even when not properly maintained.
https://www.dropbox.com/s/bvwmt5px06b5x8h/20170429_080046.jpg?raw=1
https://www.dropbox.com/s/uzznjv7jughm89v/20170429_082407.jpg?raw=1
https://www.dropbox.com/s/55b7w9e8p8b5gav/20170429_092526.jpg?raw=1

here is the pool a little later, I used duct tape to maintain the two sides at the same height, but there is really no tension in them,
https://www.dropbox.com/s/ia5e2fhgn2lfrl5/20170429_141815.jpg?raw=1

And here it is at the end of day two, the tarp is full and touching the bottom, there is still a bit of old water on the sides but the tarp is too small to go much lower.
https://www.dropbox.com/s/wbua6542hwa0ihn/20170430_152614.jpg?raw=1

And then, the "grand final", the removing of the sheet :
https://www.dropbox.com/s/isa0bzgolfvjx2b/removal.mp4?raw=1

Anyway this worked very well and my CYA is now even lower than I excpected, less than 30! Oh well, it's easier to raise than to lower :D
I'm ready to begin the SLAM!
 

Analogbytes

Bronze Supporter
Dec 22, 2016
291
Arlington, Texas
#2
Thanks for sharing a play by play. We have had several people do something similar with success. SLAMs Away!

By the way, looks like you have a great helper managing the water input (=
 
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Nitrock28

Bronze Supporter
Apr 19, 2017
16
Belgium
#4
Yes I have seen only a few posts showing this method, so I thought it would be interesting to take pictures. It is really easy to do once you have a large enough sheet.

By the way, looks like you have a great helper managing the water input (=
He is always there to help me tend to the pool, he can't wait to take his first swim!
 
Apr 25, 2017
25
Georgia
#5
This method interests me as I also have a vinyl-lined older pool without main drain.

Am I understanding correctly, that you drain the water below the tarp while you fill new water on the tarp? And this maintains pressure on the vinyl liner so that it doesn't pop out, even with a nearly full drain?
 

n240sxguy

Well-known member
May 17, 2014
1,802
Benton, KY
#6
This method interests me as I also have a vinyl-lined older pool without main drain.

Am I understanding correctly, that you drain the water below the tarp while you fill new water on the tarp? And this maintains pressure on the vinyl liner so that it doesn't pop out, even with a nearly full drain?
That is correct. The tarp separates the old and new water while still maintaining a safe water level in the pool.


Sent from my iPhone using Tapatalk
 
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Nitrock28

Bronze Supporter
Apr 19, 2017
16
Belgium
#12
Thanks Everybody, I'm glad I could help the community after all I'v learned here!

What size is the pool?

What size was the tarp?

That's Nice Work!!
The pool is 12' x 22' (if my conversions from meters are correct :p ) and the tarp is 8x5m (around 26' x 16' 1/2),
it was clearly not big enough to hold the full volume of the pool, but since you can always lower the level down a little, it was actually sufficient.

I stopped the filling once the tarp was full (water almost overflowing on both sides) and then only drained until the level was as low as I was comfortable with.
 
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Nitrock28

Bronze Supporter
Apr 19, 2017
16
Belgium
#13
Hi guys,

I'm back with some news of my pool, and some questions... :D

So I had to delay the beginning of my slam due to the installation of my solar heater. It is still in progress but now I can run my pump if I use the bypass.

Here is the full log of my levels since the beginning 6 days ago :
http://www.dropbox.com/s/ayqjp29fmd60f0u/Log.PNG?raw=1

The CYA level was initially low, and as I had a big bucket of trichlor, I wanted to use that as my CYA source. The problem is, Trichlor also contains a lot of chlorine, more than I thought.

You can see that I didn't add any chlorine after the first 10 ppm to get up to Slam level, but it climbed all the way to 22ppm quickly. I removed the cover (which doesn't let the sunlight through) during the sunny days to deplete the chlorine quicker, and managed to keep the chlorine at "reasonable" levels.

You can also see that I passed 2 OCLT in a row (My CC are 0 since I added the chlorine), so it should mean that nothing is growing in my pool :D, now I'm leaving the chlorine get back to standard levels.

The only concern I have is about my vinyl Liner, it is quite old and there are brown/green stains on the walls, especially on the less exposed side. Could it still be algae at the chlorine levels that I run? I also noticed that the stains are present only under the old water line from when I was working on my heater (water stayed at that level for about a month).

This picture shows the stains on the bottom, then you can see the old water line where the stain stops, then the actual water line.
http://www.dropbox.com/s/06rcsg38m1fhdtc/20170531_202820.jpg?raw=1

Any Idea on what the stain could be?
 
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Nitrock28

Bronze Supporter
Apr 19, 2017
16
Belgium
#15
No it's City water, the pool store tested the water before the refill and it was at zero for both Copper and Iron, I could go and check again to see what are my levels now that I drained and refilled.