Switching to TFP Method, CYA Crazy High

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M

mmh

Member
May 22, 2022
5
Mesa, Arizona
Bought this house 2 years ago, old owner used tabs, shock, and Leslie's "perfect weekly" to keep the pool maintained. It is a 15k gallon pebble tec pool with a variable speed pump and sand filter. The pool has been getting green lately and I would like to switch to the TFP method and do a SLAM, but after reading about it, I learned the importance of doing your own measurements and wow do I have some issues. I would like to use liquid chlorine as sanitizer.

I bought a TF-Pro test kit to perform all these measurements.

FC 0.5 ppm
CC 0.5 ppm
TC 1 ppm
CH 1,075 ppm
TA 160
CYA 200+

I did the 1:1 distilled water : pool water method to try and get a better reading of the CYA, it is probably ~250.

Should I do an 80% drain to get the CYA under control? I live in Mesa, AZ (suburb of PHX) so I think I will need CYA to be on the higher end of things. I get my water from Apache Junction so a full refill would cost me ~$60 but I am not sure if the sun would damage the pebble tec while I do a drain and re-fill.

Thanks!
Mike
 
Welcome to the forum!
Great decision to get a quality test kit.
You need to do a full drain or exchange. You are in that time of year that it is not good to let the plaster dry out in the heat. So you need to determine can you drain the pool quickly (Home Depot has high power sump pumps) and get it refilled before the sun shines on your plaster. Or you can do an exchange which will take more water. See Draining - Further Reading
I suggest you read through Pool Care Basics - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool
 
mmh said:
Awesome! Thanks, I was thinking about doing the no drain water exchange method. I will have to do some math to see if I need to wait to do this on a weekend since during the weekday my power is extra expensive from 2pm-8pm.
Click to expand...
Hey I did a water exchange using a submersible pump on one end and a garden hose to keep filling on the other. I was able to get my CYA to 70. I can lend you the pump if you want
 
mmh said:
Awesome! Thanks, I was thinking about doing the no drain water exchange method. I will have to do some math to see if I need to wait to do this on a weekend since during the weekday my power is extra expensive from 2pm-8pm.
Click to expand...
Get a 5 gallon bucket, time how long it takes to fill from your hose...do the same with the pump, that will help with the math.

If you do it, do it in one go....

If you need to balance output to input, (output will likely be higher rate), raise the output over a ladder to humpty dump over two ladders to create some head. I was able to balance them enough to sleep for 6 hours.
 
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Just getting back to this (not sure if necoing your own thread is allowed) but my issue is I get like 5.5 GPM from a garden hose, so it will take me ~30 hours to do a 75% exchange, but I think at that time scale there will be a ton of mixing. I've done some extra math and I generate enough power to offset the pump electricity, so I can run it for the full 30 hours.

@csheridannjaz Did you run into a lot of problems mixing? How long did it take?
Thank you all so much for all of your help!
 
That should work...I put the sump in the shallow end and filled bottom of the deep...took me about 45 hours...had very little mixing and worked just fine. Numbers came out exactly where I calculated.
 

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Did you work through the determination in the article?
Likely in your area you will need to pull water out from the deep end and add water to the surface.
 
How do you measure TDS? Or can I use CH? The temperature is easy enough to work out and in that case my DeltaT is positive (pool water hotter than fill water).

> Salt is the largest component of TDS.

Should I buy a K-1766 salt test for this then?

And just by inspection:
DeltaT = (PWT - PWTDS / 165) - (FWT - FWTDS / 165)
I know that PWTDS >> FWTDS and PWT > FWT, so that implies that DeltaT will be positive in my case, so regardless of the value I know I will want to fill from the deepest and drain from the surface.

I would like to work out the value to ballpark how bad the mixing will be.
 
Essentially TDS is salt and CH. Plus CYA for the pool water.
Fresh water TDS for your would be CH of 250 and salt of 200 for a total of 450.

Your pool salinity (appears you have been using trichlor) would be at least 1000. Likely higher. A test at a pool store may be something to consider.
 
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