CC level and dull water

[lesandov]

Hello Everyone,

I am currently having some issues with high CC level and dull water.
From Monday thru Friday, my wife is using the 17,000-gallon-pool to deliver exercising sessions to several groups of seniors during the morning. The afternoons are dedicated to children and adults. In a regular day, there are in the water about 12 to 15 people every hour from 7 to 11 a.m. and from 4 to 8 p.m. There are people swimming, walking and jumping all the time in her 8-hour shift.
Current levels are:
FC: 7
CC: 1
pH: 7.6
CYA: 20
TA: 80
CH: 100

Around four weeks ago, on Sunday, I did a 60% water replacement. After that, the CC level was at a more comfortable .5 ppm. Also I started using Potassium Monopersulfate to help oxidization process while keeping FC rather high (above 6 ppm) to prevent a CC arise.
Unfortunately, at the end of the first week I could see that CC level hit the 1.5 ppm mark. This was kind of frustrating since the FC level was kept above the 6 ppm at all times, adding 3 pints of bleach at both noon and night. Every Sunday after last water replacement I have been tossing 4.4 pounds of MPS and enough bleach to reach the 10 ppm or little above, keeping it there during the weekend. On Mondays I get sparkling clean water, but at the end of the day it is easy to see that water becomes kind of dull, clear but no sparkling. I also notice that every morning I get clearer water; I assume this is because I keep my pump running 24 by 7 (@2500 rpm from 7:00 to 20:00 hrs, @1600 rpm from 20:00 to next morning). CC level has been drifting from 1 to 1.5 ppm, but never lower
My theory is:

1. Considering the number of patrons at one time in the pool; I believe this is a I high bather load for the size of my pool which has to do with both less-than-clear -water and more organic waste to deal with.
2. Since my pool is indoor, the oxidization of chlorine by products is slower, implying higher CC readings.

I am aware that MPS reacts with the DPD used in the FC/CC test, giving higher FC and CC readings; but I understand that this interference will last only a couple of days. With this in mind, I assume that the FC/CC test should give more accurate results by Wednesday or Thursday, if MPS is poured on Sunday morning.
Under my current conditions, it seems that a weekend-long SLAMMING is not enough to lower CC level or have an OCLT good outcome. Since the pool’s schedule is kind of busy during weekdays, sparing an extra day or two to keep SLAMMING is a costly option.
I am not sure what the next course of action will be to improve water clearness and to lower CC level. Perhaps adding some extra MPS at the middle of the week or add some rpm’s to the pump.
I’ll appreciate your comments.
Thanks in Advance.

 

[needsajet]

I'm no chemist, so no comments from me on that front. It sounds like an important service you're running. If that makes it a commercial pool, there may be regulations to think about.

Beyond that, it strikes me that the filter is small for that big a job, so it could be upsized. Adding DE to the filter might be helpful Pool School - Add DE to a Sand Filter. I suspect you need to backwash often, and increasing rinse time after backwashing can be helpful.

I'm not saying anyone hasn't showered before arriving, but if it were possible to ensure that everyone has a fresh shower on the way in to the pool, you could reduce the amount of required sanitation.

Pullin' up a chair to learn more about the fancy chemistry stuff!

 

[duraleigh]

You can forget the suggestions of chlorine consumptions that we teach. You have a heavy, heavy swim load and it will take a lot of FC to keep your CC's manageable.

I don't have enough experience with mps to suggest a dosage program.

 

[lesandov]

Needsajet & Duraleigh, thank you both for your answers.

On the backwashing matter, I got to say that I've been experiencing an unusual increase in filter PSI. My clean-pressure is about 19psi and goes up to 22psi in three or four days. This causes that my the heat pump does not get enough flow to operate.

I usually bachwash for five minutes at full pump throtle (3110 rpm) and then rinse for about 30 seconds. On what I understand from your comment, probably I should take some extra time to both backwashing and rinsing.

 

[needsajet]

I can only speak for my filter, a 25", and I need about 1.5 minutes to backwash and about the same to rinse, all on high speed. If I rinse less, I see cloudy water coming out of the returns.

 

[lesandov]

You can forget the suggestions of chlorine consumptions that we teach. You have a heavy, heavy swim load and it will take a lot of FC to keep your CC's manageable.

Based on the facts, I believe you are right on this. I assume that keeping the FC level as close as possible to the shock point will help.

 

[lesandov]

I'm no chemist, so no comments from me on that front. It sounds like an important service you're running. If that makes it a commercial pool, there may be regulations to think about.

Yes, there are regulations on the matter of course. I take them in consideration in a daily basis. One is to keep zero-CYA level for Indoor facilities. I prefer to bend this a little bit to get the most out of the chlorine.

Regulations also state that about the 5% of your water should be replaced everyday. that might help to prevent the issues I've been dealing with; unfortunately, the water public service is not that reliable, which makes the task hard to accomplish.