Hello all, I've been lurking around for a while and this forum has been a very big help! I recently had to drain/dillute my 10000gal fb pool.. I became a high CYA victim 120+! and in the process became overrun with alage I tossed my trichlore pucks ( lesson learned ) and purchased several cases of liquid cholrine .. I started a SLAM on my pool.. My question is my test kit is a Taylor k-2006 and the CYA test is a turbidity test.. Right before I SLAM'd the pool I had a reading of approx 60ppm outside in sunlight, I brushed ( pool became pea soup) added 5 gallons of smart liquid shock I got at home depot and got the pool to settle at 40ppm FC this was at 7pm so around dusk I took another water sample and redid the CYA just to confirm my reading and the sample read a CYA of around 80 ish in kitchen lighting ( it had since gotten dark outside ) can the lighting cause this difference in the test? I can't restest becuase that used my last bit of test solution ? (I have some more in the mail due here in a few days ) since I'm unsure with this I split the difference and have been using the higher measurements for my pool SLAM... ( this morning I awoke to a clear pool to my surprise.. just had to brush the remaining alage off the pool walls clouding it a bit, FC was at 24ppm so I added 3 more gallons of chlorine to bring the FC to 52ppm)
CYA turbidity test and algae
- Thread starter silentguy85
- Start date
Welcome to TFP!
The lighting can make a big difference in the results of the CYA test. The test itself is pretty subjective even with consistent lighting.
Why are you running such high chlorine levels? Shock level for your water is 28ppm if you are assuming 70ppm chlorine.
The lighting can make a big difference in the results of the CYA test. The test itself is pretty subjective even with consistent lighting.
Why are you running such high chlorine levels? Shock level for your water is 28ppm if you are assuming 70ppm chlorine.
+ 1 what JohnT said. You were wise to just split the difference on the CYA test, I am curious too why you are running your FC so very high?
- Jun 22, 2014
- 47,872
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
I've heard many times on this forum that's one reason pool store readings are misleading - simply because of the indoor lighting. 
The reason I'm keeping my FC so high is because some of the algae in the shallow end had an almost yellowish color in some spots ( could also just be me being paranoid ) so to stay on the side of caution Im trying to stay a little above mustard algae shock levels and this may be overkill.. I only really have one day off to devote to getting this algae under control.. I have read high levels can damage the pool equipment but I'd rather waste a little product making sure I kill everything in one blow than drag it on over days and waste more by not getting to the right level. Especially since I'm not 100% confident with the CYA readings.. I don't plan on adding any more chlorine and plan to let it ride at 25ish ppm until 100% clear then rebalance the water... We are forecasted for alot of rain and the pool is in dirrect sunlight so I know the levels will drop off by this afternoon...
As a general principle, we would rather see you test and dose more carefully. Overdosing can have some side effects that are not helpful. The parameters we have set are there to make sure there is nothing harmful in what we suggest. It is certainly your pool to care for any way you want but the CYA readings are not far enough off to warrant an FC of 52 ppm.