Cyanuric Acid for indoor pool

What is floc, clarifier, stabilizer, cyanuric acid,
algaecide, brightener, dichlor, sodium hypo,
sodium bisulfate, ....??
Denniswiseman
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Cyanuric Acid for indoor pool

Postby Denniswiseman » Fri 07 Dec, 2012 08:43

Hi

I know that cyanuric acid is not required for indoor pools to stop UV degradation of chlorine
I want to know if there should be an amount of cyanuric acid present anyway
I use sodium hypochlorite 14.5% as a sanitiser


chem geek
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Cyanuric Acid for indoor pool

Postby chem geek » Sat 08 Dec, 2012 03:20

A low level of Cynauric Acid, say 20 ppm, will moderate chlorine's strength. An FC of 4 ppm with a CYA of 20 ppm would have the same active chlorine level as 0.2 ppm FC with no CYA. This will result in slower oxidation of swimsuits, skin and hair, slower creation of disinfection by-products, slower outgassing of chlorine, but also slower oxidation of bather waste. If you already have a UV system to help control chloramines, then that would be helpful regardless.

My wife experiences the effects of swimming in an indoor commercial pool that doesn't use CYA and has 1-2 ppm FC where her swimsuits wear out after just one 5-month winter season. In our own outdoor residential pool over the 7 month summer swim season, the swimsuits last for years in 3-6 ppm FC with 30-40 ppm CYA. The difference is likely due to the fact that the indoor pool has over 10 times the active chlorine level compared to the outdoor pool.

Note that if you are talking about a commercial/public pool, there may be state or local regulations prohibiting CYA use in indoor pools.
Denniswiseman
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Cyanuric Acid for indoor pool

Postby Denniswiseman » Sat 08 Dec, 2012 10:22

Hi
This is a private covered pool used all year round
I've just had to refill it and wanted to get an optimum water chemistry level from the start

It seems from your post that a certain level of cyanuric acid is benefical or should I keep the FC level lower
I don't have a UV system
chem geek
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Cyanuric Acid for indoor pool

Postby chem geek » Sat 08 Dec, 2012 18:57

It's impractical for you to keep the FC at a low 0.2 ppm level so instead I'd suggest you target 4 ppm FC with 20 ppm CYA. Just be aware that by not having a UV system you could get some buildup of certain organic chloramines that are slow-to-oxidize from chlorine alone. Some people use non-chlorine shock (MPS) on occassion to try and deal with this, but success is mixed (i.e. it works for some and not for others).

If you haven't had a problem with chloramines in the past, then you'll probably be OK. Try 4 ppm FC with 20 ppm CYA (you could also try 2 ppm FC with 20 ppm CYA, but that may be too low an active chlorine level unless you don't use the pool very much).
Denniswiseman
Swimming Pool Superstar
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Posts: 334
Joined: Tue 06 Sep, 2011 05:48
My Pool: 10k inground fibreglass, Telescopic Cover, Hayward Powerline pump, Quality filter with glass media, 27kw output heat pump, K-2006C test kit
Location: United Kingdom

Cyanuric Acid for indoor pool

Postby Denniswiseman » Sun 09 Dec, 2012 03:35

Thanks for that ChemGeek

It's put my mind at rest as I wasn't going to add any Cyanuric acid

I will test and try 4ppm FC with a 20ppm Cyanuric acid

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