Why does the pool store not respect the Chlorine / CYA Chart?

[NJnoob]

I had to stop by the pool store today and since my TF-100 Test Kit hasn't arrived yet, I brought in a water sample to see where my numbers are at (I tried a few brands of test strips the previous owner left me but the results were wildly varied). Numbers came in as follows:

FC - 3.0
TC - 4.0
pH - 7.8
TA - 90
CYA - 110
Hardness - 220

Their comment was my pH is ever so slightly high, but otherwise everything else is perfect, so keep doing what I'm doing (which hasn't been much so far, the pool has been open for a week). However, looking at the Chlorine / CYA Chart, 110 CYA is so high it is off the chart, anything over 60 is bad, and a 100 CYA should have FC in the 11-13 range.

So why did they tell me I'm doing a great job, while the advice here makes it seem to me I'm in trouble and need to partially drain my pool because my CYA is so high?

 

[mknauss]

Normal pool store operations. They do not embrace the FC/CYA relationship. Of course it would mean eliminating solid forms of chlorine and that is not good to the majority of their sales.

I assume you are adding bleach every day until your kit arrives? You should add about 1 1/2 gallons a day of 8.25% to keep things stable.

Take care.

 

[borjis]

No money in that.

SWG's need 70-80 CYA to maintain FC levels.

I'd say anything over that range is trouble.

 

[bordelond]

I've just started here myself, and I'm far from an expert.

What I have learned so far, though, is that our local pool store totally sticks to the "FC at 1-4 ppm" mantra. They don't even bring up cyanuric acid (CYA), which I'd have thought would've come up very early in their advice to new pool owners.

Around here, so many people just float some 3" tri-chlor pucks and forget it. On my first visit to our pool store, I mentioned early on that I had tri-chlor pucks and intended to use them for chlorination. Not a word back about CYA ... and they still sold me a CYA precursor conditioner.

 

[NJnoob]

Thanks everyone! I figured there was some financial incentive for the pool stores to ignore it.

I'm planning to drain what I can tomorrow during the day and then refill at night and add more bleach so we can swim the next day. Thanks for the recommended amount @mknauss. Testing kit should be here Monday.

 

[jblizzle]

Yeah, it is a bit of a mystery why they ignore 40 year old science.

Either they are ignorant about the chemistry and just don't know any better or perhaps it is ignored for financial gain. Each makes me wonder why anyone would trust the advice when this is not a part of it.

 

[Deb04]

I suggest that, unless you've been using pucks for a while and therefore know your CYA is high, you wait to drain until you can test it yourself. If you just add the bleach suggested above, you'll be able to swim. It would be a shame (and costly) to replace a lot of water and then learn you have to add CYA bc the pool store was wrong.

 

[NJnoob]

Thanks. The previous homeowner left me about 70 trichlor pucks and the test strips they left show a CYA of 100, so it seems likely the pool store reading is at least somewhat accurate.

The kids want to swim tomorrow so unless my drain & refill plan will prevent that, I think I'll go through with the drain & refill today.

 

[bordelond]

The kids want to swim tomorrow so unless my drain & refill plan will prevent that, I think I'll go through with the drain & refill today.

Your pool is ~38,000 gallons? That's over 11 times the volume of my little 16x8x3.5 Intex ... and mine took seven hours to fill from a garden hose.

 

[NJnoob]

It's an odd shape. I need to spend the time to get an accurate measurement, but generally it's 42' x 24' and 8' in the deep end (actually haven't measured the shallow end, but I assume it's somewhere between 3' & 4'). Took 3 hours to fill high enough for opening with 4 garden hoses filling it up.

 

[bordelond]

It's an odd shape. I need to spend the time to get an accurate measurement, but generally it's 42' x 24' and 8' in the deep end (actually haven't measured the shallow end, but I assume it's somewhere between 3' & 4'). Took 3 hours to fill high enough for opening with 4 garden hoses filling it up.

That's some awesome water pressure!

If you can fill your pool in 3-6 hours, and if you hustle with the draining (half the water, right?) and sanitizing, sounds like you can get it ready for swimming by tomorrow.