CYA keeps rising even with removing all chemicals and diluting pool over a month

[Raven7146]

Hi, this is my first post here. I’m very confused..
We bought a house with a 6yr old free form concrete pebble tec pool approx 11,000 gal with DE filter.
My strips kept reading high CYA and FAC but all other areas pretty much balanced. Water is clear with no algae or other issues. It’s winter so the water temp is 40-50 degrees.
Jan 20 I brought a sample of the water to Leslie’s and the readings were
FAC 10
TAC 10
CYA 100
TA 110
PH 7.8
Copper 0
Iron 0
TDS 800
Pho 0
At the time there were pucks in the auto dispenser attached to the pool equipment. Leslie’s told me to remove them and don’t shock (I had not shocked or added any chemicals from the time we bought the house at the end of Dec, the only chemicals were the pucks in the auto dispenser.)
Here are the readings 32 days later after the pucks where removed, no added chemicals or shock, about 1/8 of the water added (was low due to evaporation) via hose and heavy rain. We are outside Austin and can’t imagine the rain being acidic.
FAC 5
TAC 5
CH 380
CYA 150 (??? AFTER removing chlorine pucks and not adding chemicals since the last reading of 100 AND diluting the water)
TA 100
PH 7.8
Copper 0
Iron 0
TDS 1200
Pho 1000

They’ve told me to add something to bring down the Pho and can’t explain why the CYA went up 50ppm in a month after taking away all chemicals and adding a LOT of water.
The TAC and FAC are better but still a bit high.
I don’t know what to do. If draining and adding water brings down the CYA and mine went up.. I’m lost.
Leslie’s also said they have a product called Bio-Active that brings down CYA but the reviews are mixed and it’s SUPER expensive.
Any help would be most appreciated.

[Denniswiseman]

First of all get your own decent FAS/DPD testing kit (Taylor K2006C or TF100) pool stores and strips testing are unreliable and the difference between tests could be down to operator error
Topping up because of evaporation won't dilute your CYA or CH. You have to do a partial drain and refill (draining 50% of your water and replacing it with fresh water will reduce your CYA by 50%)
Use liquid chlorine (Sodium Hypochlorite or plain bleach) your pucks add CYA.
For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm
High CYA renders your chlorine ineffective so you would have to have use more chlorine (A CYA of 100 needs a minimum of 8 and a target of 11-13 with a shock level of 39) A low level of 10 would be on the way to an algae bloom
Don't worry about Phosphates as your partial drain and refill will reduce them as well
Looking at your PS figures you will have to raise your CH after refilling unless your fill water is high in Calcium
When you test with your own kit come back with the figures and we can sort out your pool
FC:
TC:
pH:
TA:
CH:
CYA:

[Teapot]

Test strips, you may as well through your shoes into the air to knock down the clouds. (love that phrase)
CYA is difficult to measure as it's a turbidity test (cloudy water) so the increase can be through not having chemicals to oxidise the waste and pucks usually contain some clarifyer so not always through an increase in CYA, temperature can also effect it.

You may not imagine rain to be acidic, I can assure you it normally is below pH7.
Phosphates could enter through your water top ups, some areas add high levels to protect their pipework, if that is the case rain water is better. Ideally phosphates should be 0 as that is a source of food for algae, add that to the high CYA level and you are heading for a green swamp.

I second what Dennis said, get your own test kit, then you are the only person using it, you repeat the test in the same way so getting consistent results but you should take the water sample from the same point in the pool at the same depth.

[Raven7146]

Thanks! Ordered a TF100 and Speedstir. Will post results later.
I have something else that doesn’t make sense:
There are people that use chlorine pucks and shock all the time and their CYA doesn’t sky rocket.. why si that?
If Triclor increases CYF by 6ppm and Dichlor adds 10ppm CYF.. how can someone ever use either of these consistently without eventually getting to over 100 ppm of CYF if nothing but draining and refilling will lower CYF?
I had a pool in Houston that I only used pucks and shock and never had a CYF issue. Just can’t wrap my brain around this one..

[Denniswiseman]

Thanks! Ordered a TF100 and Speedstir. Will post results later.
I have something else that doesn’t make sense:
There are people that use chlorine pucks and shock all the time and their CYA doesn’t sky rocket.. why si that?
If Triclor increases CYF by 6ppm and Dichlor adds 10ppm CYF.. how can someone ever use either of these consistently without eventually getting to over 100 ppm of CYF if nothing but draining and refilling will lower CYF?
I had a pool in Houston that I only used pucks and shock and never had a CYF issue. Just can’t wrap my brain around this one..

Congratulations on your purchase, you are on the way to be in control of your pool and maybe convert others as well. You will find that the cost will be paid for by reducing your PS dependance
What I quoted you are solid facts, the CYA binds the chlorine so that it can be in solid form and easily handled.
When I first had a pool I used Trichlor pucks and my CYA increased quiet high, I now use Liquid chlorine but this adds salt (Sodium) which isn't a problem, if you have a salt water chlorine generator you need to have about 3000ppm for it to operate correctly.
The people who use pucks continously probably don't test themselves, go to a PS, be sold god knows what and be in a constant Yo-Yo, They may have leaks and are constanty topping up thus diluting it or they may be blissfully unaware (as I was) of the consequences of high CYA untill they have an algae bloom
Check out Chlorine / CYA Chart and Pool Levels

[Teapot]

If Triclor increases CYF by 6ppm and Dichlor adds 10ppm CYF.. how can someone ever use either of these consistently without eventually getting to over 100 ppm of CYF if nothing but draining and refilling will lower CYF?
I had a pool in Houston that I only used pucks and shock and never had a CYF issue. Just can’t wrap my brain around this one..

Not IF, it does exactly as Dennis described. With splash out, evaporation (especially in Houston) rain, winter lowering of levels and fresh water top ups it is possible to get a situation where it takes many seasons to get that high but it does in most cases happen. It is just not well enough known for people to listen to and dip strips can't measure it well etc etc.
CYA is more important than pH in your pool. An excess of non stabilised chlorine will slowly oxidise the CYA and the levels can drop over winter, possibly due to a bacteria that like CYA when the chlorine level is 0.
Still the good news is you are on your way to understanding pool water chemistry and unlocking how easy home pool care can be.

[Teapot]

I guess that was someone not yet ready for the truth behind packaged pool chemicals. We can't always give you the answer you want to hear, we will give you the factual answer.