Neighbor's CYA off the charts - where to start?

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J

jfdub

0
Feb 23, 2016
54
New Braunfels, TX
Hi all,

My friend/neighbor has an IG pool with the following details (He currently has a pool service - I'll be working on convincing him to use the TFPC method):

18,000 Gallons with waterfall
Plaster/Pebble

DE Filter (I think Hayward)

Jandy Stealth Pump (I know it has two speeds, not sure any other details)

Second pump for cleaner
Filled from community well

He asked us to house sit while they went away on a 2 week vacation and told us to feel free to use the pool. There were some issues with his DE filter (30 PSI with huge load on the pump) and the water was getting cloudy so I physically cleaned the filter and replaced with 6 lbs of DE as indicated on the side of the filter. Since I'm having one built and need to learn the TFPC method I figured I'd try testing his water (I have a Taylor K-2006 test kit). Here are the results

FC - 0
CC - 0
pH - 8
TA - 200
CH - 380
CYA - Off the chart - I can only put about an inch of water in the tube when I lose sight of the dot

I've been reading and I assume CYA is so high because he uses chlorine tabs - I'll try to talk him into bleach when he gets back.

So is the first step here a partial drain/refill and recheck for CYA? Can I check for CYA immediately or do I need to wait some length of time before I check (with my rapidly dwindling reagent supply - I've already ordered the 16 oz refill from Amazon!)? Also, I've read that there may be some usefulness to filling at the bottom and draining from the top due to the differences in water temperature - does that sound right (cold stays at the bottom and hot stays on top)? His pool water has to be above 90 here in the Hill Country with all the heat we've had and the well water is easily ~75 degrees.

With that information, do you think I'm on track or have any other recommendations? I'm thinking:


  1. Get CYA levels fixed (30-50 ppm)
  2. SLAM
  3. Adjust PH to 7.2 and let it rise back up to 7.8
  4. Deal with the TA
  5. Fix the CH

What do you think? Thanks for reading and any suggestions you have!
 
I have to ask if he asked you to change his pool :)

I would first find out the CYA level as follows:
Carefully measure 2 cups of pool water, pour in clean mixing bowl. With same measuring cup, measure 2 cups tap water and add to bowl. Do it again so you have 2 cups pool water and 4 cups tap water. Mix it up well. Draw the 7 ml sample from the mixture. The true CYA will be three times what the test says, e.g. if the test says 50, the pool is 150.

If that doesn't work try 2 cups pool water and 6 cups tap water. Pool is 4X test reading.

I'd probably do what he said for maintenance, and give him a call and see if he wants it fixed. I'd measure it up to get the pool volume and use Pool Math to find the right amount of chlorine.

I wouldn't swim in it until it has FC above minimum for the CYA level. Be aware that if you add liquid chlorine to the right level, it might go white/blue cloudy as the dead algae carcasses show up.
 
CYA 30 for SLAM would be great if you can get down that far. CYA 50 is quite do-able. Be cautious about high water table for drain/refill
I would do pH before SLAM
SLAM if needed (high CC, failed OCLT or presence of algae)
After SLAM (or during) CYA 50 for that hot sun
TA yep
CH will be dictated by the drain/refill, and there won't be much you can do about it, but high CH is manageable.
Good fun if you get to do it! That pool is going to be sweet :)
 
I would say getting the pH does should be first priority unless you plan to drain right away then deal with the CYA, note we have found through testing that inaccuracy introduced through the dilution method tends to introduce so much error that dilution beyond the 1 to 1 pool water to tap water level and multiplying the reading by 2 tends to make the results questionable. Also once you reach the point of knowing you must replace over 75% of the pool water (with a CYA exceeding about 200 ppm), there is little reason not to go ahead and do a full water replacement and start fresh.

You do need to give the water time to mix before retesting CYA after a partial drain, as to the drain from top vs bottom, it depends on the temperature of the pool vs the fill water. If the fill water is cooler than the pool then drain from the top and fill from the bottom while the circulation pump is turned off.
 
I don't know about drain from bottom, fill at the top, or vice versa. I don't get a positive feeling about that. I think the CYA diffuses pretty well.

There's a tarp method that sounds good, but I've heard an expert here say it doesn't work. Here's the link:
New User - Doing first drain - What do I need to know?

This is the video as he removes the tarp when he's done:
Dropbox - Video May 08, 7 20 37 PM.mov

I know the trick is to draw all the drain water from below the tarp, so you have to keep the tarp off the drain and/or skimmer(s)
 
I agree about dilution if measuring 7 mls without a pipette for sure. Diluting with a larger quantity reduces error to a manageable level, particularly if each measure is done carefully and to the same personal error (reading of the line on the measuring cup). I just like to know roughly what sort of water dilution is faced. I agree it's likely to be a major replacement.

For example, if it's 120 CYA, you'll need to replace about 60% of the water. If it's 250 PPM CYA then about 80% needs to be replaced. For a 20,000 gal pool, that's 12,000 gallons vs. 16,000 gallons. Maybe no big deal on city water, but could be important when you're on a well.
 
needsajet, my point was that there really is not much use in most situations test beyond a 1:1 dilution with tap water rate giving a max reading of over 200 ppm CYA, since this point would require replacement of over 75% of the pool water regardless of the exact number. At which point complete water replacement is not that much higher of a burden regardless of water source. Sure at a reading of 120 ppm CYA that is a big difference with a 20,000 gallon pool, however at anything over 200 ppm CYA and a 50 ppm target the replacement difference is less than 5,000 gallons regardless, 200 ppm, 15,000 water needs to be replaced, 400 pprm 17,500 gallons need to replaced, etc. Add to this how hard it is to judge percentage of pool water left in a regularly shaped pool much less an irregularly shaped one and you get a strong argument to just replace it all and be safe. Now of course if you are in a situation where it is not safe to empty a pool due to potential floating, vinyl liner lift, etc that is another topic.
 
We're going to replace 3/4 of the water (until we get to 50 CYA) using the "cold water sinks and warmer water stays on top" method. I have a sump pump that we'll keep ~2 ft under water and throw the hose in the deep end. He's texting his pool maintenance guy talking about the CYA (who knows?) 300+ and FC levels at ZERO and the pool guy says "it's normal to replace your pool water every 5-7 years". HA!

We're good friends and in this together so I think he's going to start using bleach instead of tabs and testing every 1-2 days for FC and CC and PH. I can't wait for my pool to get finished and start learning the water chemistry - this site is a great tool for everyone with a pool. I'm getting a Stenner pump and I think he is too - you guys make this so simple it's crazy! I had a pool in my old house and couldn't for the life of me figure out how to get it clean - I wish I knew of this site many years ago!

Thanks for all the advice, I'll update with new readings after we replace the water.
 

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Excellent! I'm really interested to hear how you do it and how it works. Would you be willing to log the water going in? Such as 'date', 'time' 'time filling' and 'gallons per minute'? You could time how long it takes to fill a graduated pail or something to get a rough idea of flow? Certainly not necessary and don't bother if it's bother!
 
We measured with a 5 gallon bucket today. 60 seconds to fill with the community well - 40 seconds to fill with my pump from his pool. So we put the pump and well hose in the pool at 6:19PM CST and measured 4 1/2" from water to the top of the coping. We got back from dinner around 9:15PM and the water was 6" from the top of the coping. The water is still really warm so I'm hoping the cooler well water is staying at the bottom. I think he's going to run it all night and we'll check CYA sometime tomorrow.

This is fun! :)
 
We remeasured yesterday and CYA is 90. Still high but fairly manageable. It's raining today so he'll see if that and splashing around the pool will bring it down naturally. We added 5 bottles of bleach last night and got the FC to 12.5. I'm heading out of town but he showed me 8 bottles of bleach he had in his car before I left. Nice!

On another note, why has Clorox stopped putting the percentages on the bottles? I'm pretty sure they're 8.25 but C'MON!!
 
I just want to correct something I wrote in this thread. I bumped into an old thread where Chem Geek said that CYA diffuses poorly. So I retract "I don't know about drain from bottom, fill at the top, or vice versa. I don't get a positive feeling about that. I think the CYA diffuses pretty well."

So how's it going? Did you get rid of the cloudiness?
 
Yes, it does seem that the colder water remained at the bottom and the warmer (existing) water was at the top and drained with the pump which was ~12" under water. The pump was a little faster than the hose so he had to shut it off every once in a while but it worked well!
 
Hey I hope you're still around. I'm quite interested in this... What was the starting and ending CYA after the bottom fill / top drain? And was the pool water pretty warm compared to the tap water?
 
needsajet said:
Hey I hope you're still around. I'm quite interested in this... What was the starting and ending CYA after the bottom fill / top drain? And was the pool water pretty warm compared to the tap water?
Click to expand...

CYA was estimated at 300+ since I could only get about less than halfway to the 100 line before I lost sight of the dot. After the first ~24 hour drain/refill it was down to 90. He's now at 40 after another drain/refill.

The pool water was over 95 degrees and the well water was 70 or so. So not very scientific but I believe filling from the bottom and draining from the top helped save some extra drain due to the temp difference.
 

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