FC of 15 / CYA of 55

[Lawtyger]

Just got back from a week long vacation and dying to jump in the pool. But, wanted to confirm mostly for my 3 year old that it is safe to jump in without lowering the FC first. Current readings are:

FC - 15
TC - .5
pH - 7.4
TA - 70
CYA - 55

 

[kimkats]

Let him in!! Here is the chart:

Pool School - Chlorine / CYA Chart

It is safe to swim if the FC is just under the SLAM level for you CYA. As you can see you are well under it! CANNON BALL!!!!

Kim

 

[proavia]

Reference the Chlorine/CYA Chart: Pool School - Chlorine / CYA Chart

It's safe to swim anytime the FC is between the minimum and shock level listed for your CYA level and you can clearly see the bottom of the entire pool, and your pH is within the recommended range.

 

[Lawtyger]

Great - now a followup question. I know that chart says my target FC should be 4 but the other chart here suggests it should be higher (Chlorine/CYA Chart).

I was thinking of maintaining the target FC at between 8 and 10. I have battled a few mustard algae instances in the last 6 months and question whether I needed to target a FC higher than suggested in the one chart.

 

[kimkats]

Your pool has told you that answer.....yes. Go higher to keep it gone.

 

[Lawtyger]

^ good point.

 

[proavia]

If your CYA reading falls between the listed numbers on the chart, always round UP to the next number. With your reported CYA of 55, you would use the levels for CYA of 60.

On the Pool School - Chlorine / CYA Chart - for CYA 60, minimum is FC 5, target is FC 7-9 and shock level FC is 24.

Keeping it a little higher than target may help keep the mustard algae away a bit better.

 

[Lawtyger]

On the Pool School - Chlorine / CYA Chart - for CYA 60, minimum is FC 5, target is FC 7-9 and shock level FC is 24.

To make sure we are on the same page, I have a SWG and the chart for a SWG doesn't give a range like 7-9 and actually shows target as Much lower. That's why I asked the follow up question, because following what link everyone provided say I would be targeting with a SWG a FC of "4" with a CYA of 60.

Why the target differences in the charts for SWG and non- SWG pools? Clearly following that SWG chart I am aiming quite low targeting FC of 4 as it says???

 

[kimkats]

SWG pools have FC being added the whole time the pump is running. A non-swg pool only has FC being added once a day for most people so it has to "last" all day/night so will be higher and float down as the sun and stuff uses it up.

Know any of the levels are "ranges". There is always an outlier and you just might be one. We target the medium and have others adjust as needed. Each pool is different so we do what the pool likes/needs when it shows us what it wants.

Kim

 

[proavia]

Oops - sorry, I missed the SWG.

Kim is spot on in her explanation of why there are different numbers for SWG versus non-SWG chlorination methods. The ranges are a baseline recommendation - cause you have to start somewhere. Personally, I use a slightly higher range for my measured CYA - because it works for me and my pool.