Confused about FC

Jul 9, 2015
6
Kelowna
Hi guys,
We have a new above-ground 10'x30" steel-frame pool.

We filled it up and the kids played for a few days and then I found this website and realised that I needed to put chemicals in the pool. The water had got a bit cloudy (I think my youngest may not have been getting out to pee...) We drained the pool, scrubbed it and re-filled it.

The kids played in it for a day or so when we first re-filled it before I had a chance to get to the store for bleach and a test kit, but it was not cloudy at all this time (we gave the kids a big lecture!)

So, I bought a simple test kit (NOT strips!) and put the appropriate amount of chlorine in (as determined through the pool math calculator).

When I went to check the levels an hour later, the chlorine was not registering.

I added the same amount of chlorine again and tested 30 minutes later and then again a few hours later and still at zero for chlorine.

I then read that it may be that the pool needed to be shocked, so I did the math on that and added the appropriate amount of bleach, as well as some CYA in a sock in the skimmer basket (the temp. has been in the high 30s recently so I was worried that the heat from the sun was burning up the FC quickly). I let the pump run all day and tested the levels and the chlorine was off the chart as was the PH. That was three days ago.

Two days ago I tested the levels again and both Ph and FC had come down but were still at the top of the scale and too high, so I left it for another two days.

Today I checked the levels and FC is not registering at all, but the Ph is perfect.

How can I get the FC to the correct level without altering the Ph? and can my kid swim in it like this (he's desperate, having had to wait three days already)?

I'm really confused by all the chemistry... any help greatly appreciated!
Thanks!
Joy

FC - zero
Ph - 7.6
Capacity of pool: 1236 gallons
10'x30"
 
Welcome to TFP!

You really can't go two days without testing chlorine levels. Without knowing your CYA level and what levels you are seeing with FC, we really can't offer much advice.

Though high chlorine levels can interfere with pH readings, chlorine and pH are not at all related and are managed separately.
 
That's a very common test kit. It actually doesn't test FC (Free Chlorine). It tests TC (Total Chorine). The 3rd type of chlorine we are concerned about is CC (Combined Chlorine).

Free Chlorine is the chlorine that is still good. By good I mean available to kill (oxidize/sanitize) the bad stuff in the water.
Combined Chlorine is basically used up chlorine.
Total Chlorine = Free Chlorine + Combined Chlorine. It's kind of useless to test for Total Chlorine if you are having problems like cloudy water & don't also know what the Free Chlorine and/or Combined Chlorine levels are.
 
The test kit said that if you test the water within 10 seconds, that gives the FC reading and then waiting 5 mins gives you the Combined Chlorine reading... so I was going off that.

Bottom line, can my kid swim in it as it is or is it dangerous?

We don't have a ton of money, the pool itself was a gift from my parents for their grandkids and I have already spent more than the cost of the pool on chemicals/cover/vacuum/test kit etc. The FAS/DPD chlorine tests that I have seen online are the price of our whole pool. is there no way for me to do this method without buying one?
 
Pool School - Guide for Seasonal/Temporary Pools

I'd follow that guide for a pool that small. If need be, drain and start over if the water looks suspect right now.

Your pH is going to rise because likely the TA in your water is higher than optimal. If your TC is zero, you need more bleach! You also need some source of acid to bring the pH down when it rises. Muriatic acid is cheapest but for a small pool, powder pH reducer is simpler.
 

Enjoying this content?

Support TFP with a donation.

Give Support
Chlorine level is set based on CYA and the Chlorine CYA Chart. Always keep FC at or a little above target and never let it drop below minimum or the pool will be unsanitary and algae will grow.

It is safe to swim when
PH is 7.2-7.8
FC is above minimum
FC is below shock level
Water is clear
 
Ah - you didn't mention that you'd get a chlorine reading after a few minutes. That is an indication that you have no FC & the TC is all CC.

Bottom line is I wouldn't let anyone in the pool without FC.

Your best bet may be to drain & refill the pool again. Then immediately add enough bleach to bring the Chlorine level up to 3 or 4 ppm. You then need test every day & make sure the level doesn't fall below 2ppm during the afternoon. After a couple days you'll know how much to add in the evening to maintain the minimum through the afternoon when the sun is burning off chlorine. Oh yeah, don't forget the CYA.
 
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.