Confused about chlorine recommendations.

Get your CYA below 80 and then go by the recommendations.

Pool Care Basics

Overnight Chlorine Loss Test

SLAM Process

PoolMath

FC/CYA Levels

Test Kits Compared

If you have any type of water restriction, like, if you are calling the county ahead of time…..definitely do the diluted CYa test first and foremost. You only wanna drain X% and refill once. Knowing your CYA as accurately as possible will set you up for a once and done partial drain/refill. Welcome!!!

ms108 said:

Recently got rid of my pool guy who apparently wasn't doing the best job with my pool. I recently got a taylor kit & the app, and I'm confused by the chlorine recs.
It's recommending bringing the chlorine levels to 9-15? I thought these were unsafe levels.

The CYA is super high, beyond the readable range. I'm guessing 120 based on the 100 cut off. Could that be why the recs are so high?

Numbers:
FC: 0.2
pH: 8
TA: 120
CH: 225
CYA: 120

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9-15 is perfectly fine to swim in as long as the CYA really is ~100. After you exchange water to reduce CYA, make you you don’t put any more products with CYA in them (trichlor pucks or dichlor powder). And if you get cal-hypo it’ll raise your calcium levels too high as well and you’ll have to drain water to reduce that as well.

The important thing to get your head around is that with CYA in the water you can easily have not enough chlorine, but you hardly ever end up with too much chlorine.

Any FC up to SLAM for the respective CYA (see FC/CYA Levels) is safe to swim in.

When CYA is 120, then you really need 9-15ppm of FC (more towards 15, rather than 9 actually), anything lower can quickly evolve into an algae bloom. To SLAM at that level would require 47ppm of FC. Sounds crazy, and is crazy. Not because this FC level would be unhealthy or wearing out materials (at this CYA level, very different story with no CYA at all), but because it costs you crazy amounts of liquid chlorine to get there and maintain it.

When CYA is 40, the target range would be FC 5-7. But anything up to SLAM FC of 16 is just as fine. Maybe a bit wasteful in terms of required liquid chlorine amounts, but absolutely fine in terms of bather comfort.

As a comparison: The equivalent to SLAM FC in a pool without CYA (say your local indoor pool), would be FC 0.64ppm (yes, the decimal point is at the correct position). But regulations allow them usually to operate up to something like 4ppm (depends on local regulations) independent of CYA levels, which - without CYA - is a brew of its own.

That is the big problem with what the pool stores tell you - they treat FC and CYA as independent parameters.

ms108 said:

On phone with the County now. Is there a calculation to figure out how much water to drain to reduce CYA by X?

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County shouldn’t have a problem with it, just drain it into your sewer clean out. I gave my water district a heads up when we will filled, but they didn’t seem to care either.