Chlorine consumption is through the roof

[langerking]

Here are the measurables as of this morning:

FC: 2.0
CC: 0.0
pH: 7.7
TA: 65
CH: 100
CYA: <25

I just completed a SLAM 7/18/16 - 7/22/16 which consumed well over 10 gallons of 10% bleach. The OCLT only had 0.4 ppm loss, so not like it was marginal or anything.

I know the CYA is low and I have put the sock back into the pool today (with some CYA powder). However the CYA reading is strange. A few weeks ago I measured it and found it low. I added some via the sock and measured it on 7/14/16 right at 40. Now, less than 2 weeks later I am filling the tube to the top and can clearly see the black dot at the bottom. CYA doesn't just drop, I haven't drained the pool at all, minimal rain during this time, my water level is very consistent. I am struggling with the pH too, it is rising very quickly which seems odd with my alkalinity being only (60-70). I put it at 65 because the solution started turning but didn't become red until the 7th drop. For example I added acid on 7/13 and got my pH to 7.3. On 7/16 it was already up to 7.6. It tends to keep climbing too, turning such a deep shade of pinkish purple that it's off the charts, I log it as 8.0 plus and stock up on acid!

Back to the chlorine: I have to add 100 oz of 10% bleach just to maintain it. I am targeting an FC of 5.0

I used to be able to maintain chlorine with about 35 - 50 oz of bleach per day in the summer. I am wondering what could be causing the chlorine loss. The water looks great, very clear but there is something weird going on with the CYA. Is it possible the R-0013 is bad and I am getting a bad reading? Organic matter? How much organic matter is a problem? I get a frog or 2, some spiders and insects in my pool every week and of course I remove them. Not many leaves, there is a bit of debris getting in from surrounding trees but my screen enclosure keeps most of it out.

 

[needsajet]

Your daily FC consumption is around 3.5 ppm which is on the high end of normal. Is the pool is in full sun and getting used a lot?

What you're describing is often a pool that didn't quite get SLAMed enough, or maybe has some hidden algae somewhere still alive and contributing.

It sounds like your CYA was low, so wait for your most recent addition to fully dissolve. If your FC loss is related to the CYA level, your chlorine consumption should drop a bit.

The TA test should be taken to the point of "Barbie pink", then one more drop added to be sure the color doesn't change any more. The reading is total drops minus that last drop.

For the CYA test, be sure you're following the tips on CYA testing. Hold the viewing tube by the top so light can get into the tube. Keep the viewing tube at waist height with your back to the sun. Glance at the dot, look away, glance again. If you don't see the dot right away, you're done. Test multiple times by pouring the solution back into the mixing vial, invert to mix or shake it, and test again. Test as many times as you like. The CYA indicator solution is pretty stable, so it's unlikely to be bad reagent.

 

[langerking]

I am trying to understand why the CYA is so low. I checked again this morning and the test came up again with a very clear solution - whole tube filled and can see bottom easily. But recently I tested it and it was much more cloudy, guessing the measurement would have been about 20 - 25. I know that it can take a few days for the CYA to get absorbed by the water so I don't want to be adding to much. I try to add a little, wait and then test.

I will get in the water today and brush under the ladder steps and anywhere where algae could be lurking.

 

[pooldv]

CYA should show up in the test about 24 hours after it is dissolved.