FC low with SWCG. Advice?

Jump to latest Follow Reply
C

chrishick

0
Jun 14, 2016
13
Sarasota FL
Hey TFPers,

This is my first request for help. I posted some advice on a few threads yesterday to try and help out before I jump in with my request. Trying to contribute......

Anyway, I just fired my pool guy, found the TFP forums and bought my first K-2006 test kit. I've been doing a lot of reading since then. I had a Pentair IC20 that was 8-9 years old and had not been working for a year or two. When it was working, I think it was set at 40-60%. I replaced this with an IC40 cell, I figured I could run it at 20-40% and it would last longer that way. I fired my pool guy because all he did was test FC, dump in 1/2 gallon of chlorine and haul butt. I timed him one day and he was there literally 1 minute 40 seconds. I figured for $70 a month I could do the same or better.

Well, it's been about a month since his last service. I was running the SWCG at 40% and last week testing with my new kit I had 0 FC. I've bumped it up to 100% for the last 2 days. Monday I read 2.2 FC and yesterday I read 3.4 FC. For an over-sized cell running 100% I would expect it to be way higher than that. The water looks great, BUT I've noticed that it seems to be just a little hazy. I could be wrong, but it just doesn't seem to sparkle like it did before. Maybe just my imagination? Reading the forums thinking I may have an unknown algae bloom that is eating up my FC, I did an OCLT last night. I lost 0.6 FC and had 0.2 CC. I may have screwed up the test results a little though. I took my first test at around 5:30pm but the SWCG runs until 7pm, so that could have skewed the results slightly. I took the second test this morning around 5:30, so 12 hours later. I will do another OCLT tonight to verify the results. The pump runs about 10 1/2 hours per day.

My latest test results are

pH 7.5
TA 90
CH 280
CYA 70
Salt 3,800

Also, my phosphates are something like 2,800. I know a properly chlorinated pool shouldn't have a problem with phosphates, but I might get rid of them just for piece of mind.

So, I don't think I have an algae problem. What else would explain the low FC numbers? What does everyone think?

Thanks in advance.

Chris
 
HI Chris,

To get a true night reading for the OCLT you need to make sure the SWG is off before you test at night. I would give it at least half an hour with the SWG off before you test. Also make sure that there is no sunlight on the pool when you take the reading.

You can also test using the 10ml sample to save on reagents. It still sounds to me like you have an underlying algae bloom happening from what you describe.
 
Welcome to TFP, Chris.

First, great job on getting a quality test kit. The first piece of advice is to go ahead and use a 10 ml sample of pool water for FC test and then multiply by 0.5 instead of 0.2. This will save you some reagents.
For the OCLT, You really want to get the readings after the sunset and before sunrise. If this is not possible, try to get as close as possible.
Running the SWG after the 530pm test might have impacted OCLT. So I recommend you do that again. You want to make sure you test the water at least a half hour after any chlorine addition.

Since you think your SWG might not be performing as expected, I strongly encourage you to get your FC up to maintenance level on the FC/CYA chart for a CYA of 70. I would use the values for the liquid chlorination until we get that sparkle back.

The real experts will be on shortly with their expertise


Sent from my iPhone using Tapatalk
 
Welcome to the forum :wave:

If the FC was below 5 ppm for an extended period of time you likely do have algae. As it seems you are aware OCLT should be done with the cell off so you should redo it but you should also know the primary use for OCLT is to know when SLAM is complete. It can be used to determine if a SLAM is needed but that is usually done when there is unusual FC loss and the water is clear since your water is a bit hazy if it were my pool I would SLAM for at least a day or 2 then do the OCLT.

+1 on the 10ml sample save those reagents
 
I'd agree with Jezza, been in the same spot as you, thinking SWG working fine, but not keeping up with FC demand. While water was clear, it wasn't sparkly, did a slam and fixed the issue.
Also, check this link http://www.troublefreepool.com/threads/122980-Formula-for-SWG-Pump-Runtime.

Matt wrote a great program to help determine system run time, but first you will need to know what your daily FC usage is due to bathers, sun, etc. Really helped me a lot

In doing my OCLT tests, and slam, I disconnected my Pentiar IC40 by unscrewing the cable from the box on the wall, did all my testing with it unplugged. Used bleach to do slam, and will use bleach now after slam to tweak my chlorine readings instead of trying to adjust SWG every day. SWG is a slow and constant chlorine producer, so the results from 1 hour to the next won't show much.

You are on your way with a good test kit, trust your results. If you lose chlorine overnight, you've got some organics growing. Also, clean your filter out, in my case it was full of the algae and some ants that went for a swim.
 
Just did some quick math the IC40 will produce .5 ppm FC per hour at 100% in a pool your size so at 10.5 hours run time your are producing 5.25ppm if you started at 0 ended at 2.2 that is 3 ppm consumed by sunlight and whatever is in the pool not an unreasonable amount especially if there is a small amount of algae to deal with.
 
All of this only once you pass the OCLT, here is a chart that will help you know how much to run your SWG. There is a link to the instructions in my signature if you want to play with the calculator but really the chart should tell you everything you need to know.

Most pools lose between 2 and 4 ppm of FC a day. You can determine this by getting your FC to higher than needed. For example, if for your CYA, you need to be 5 ppm of FC, move it up to 8. Test to ensure it is 8, then wait 24 hours and test again and subtract the new value from 8. That is your daily loss for that day. The more times you do this, you will have a better average.

Make sure that the FC is still on the high side based on your CYA. Then fire up your SWG and pump based on the chart. Then monitor daily and see if it is keeping up. If not, then increase the % or the run time and vise versa. Once you feel that the SWG is keeping up with the demand, you can let the FC fall closer to the Target for your CYA.

 

Enjoying this content?

Support TFP with a donation.

Give Support
Thank you! I have a spreadsheet that I am using to track my testing and I had already copy/pasted your calculator into that spreadsheet for handy reference.

I think my run times will vary based on season and air/water temperature correct? My pool equipment is integrated with my home automation system and currently runs from 1.5 hours after sunrise until 1.5 hours before sunset. So on winter solstice it only runs 7.5 hours and summer solstice it runs almost 11 hours. I wonder if I could come up with some sort of temperature/sunlight formula to calculate run times? I love to over engineer things!!


Sent from my iPad using Tapatalk
 
Hey guys,

I need a little help. I turned the SWCG to 100% Sunday evening. My FC levels are as follows

Mon 2.2
Tues 3.4
Wed 5.4
Thurs 3.0 OCLT=2
Fri 0.5 OCLT=3

So it seems like the SWCG was staring to catch up, but now things are definitely getting worse.

My CYA results are the following

7/9 PAP = 100
7/17 PAP = 70
7/17 ME = 70 (My first test. Was glad that my # matched Pinch A Penny. Wow, I might actually know what the heck I'm doing here)
7/21 ME = 40 (Thinking I must have read it wrong)
7/22 ME = 45 (Well,I'm close to yesterday so maybe I am doing it right)
7/22 PAP = 100 (I doubt that my CYA went up without the addition of CYA)

So my questions are

1) Do I trust my CYA readings? Where did 25-30ppm CYA go so fast? I thought the only way to bring CYA down was drain and fill.
2) Using the CYA/FC SLAM ratio 40/16 50/20 60/24 70/28 my FC should be around 16-20. Will it hurt anything if I go to 28 FC just to be safe??

Thanks for the help!!
 
Your CYA will not go up on its own. It has to be testing error.

Was the lighting different from one CYA test to another. It is important to do it in the sun light about the same each time. Read up on testing CYA in other threads....

Your SWG will always have a difficult time "catching up" unless it is way oversized. Use bleach to bring up the FC level needed and then let the SWG maintain.
 

Enjoying this content?

Support TFP with a donation.

Give Support
You must log in or register to reply here.
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.
Top Bottom
Back
Jump to latest Follow Reply