Can't Raise FC

[poolmedic244]

Folks -

I've got my Autopilot Digital set to 50-60%. I've been testing the water every day and no matter how hard I try, I can't seem to get the FC above 2 or 2.5. Shouldn't it be producing much more chlorine at this setting threshold? Yes, I've passed the overnight test, and my CYA is somehwere between 50 and 60.

Any ideas? This thing should be going at 30% to achieve these numbers!

Thanks for the advice!
/Joshua.

 

[wireform]

Medic
The cell is a maintainer it won't bring up the chlorine level from zero before you have a new algae bloom. You need to bring it up with LC first and then maintain a level with the cell. Don't skirt danger with lower percentage but rather start high and back it down to see where it replaces the lost daily FC due to UV and bathers. I run mine on the hot side target +2 ppm for extra insurance.

 

[poolmedic244]

So you are saying my CYA isn't the problem, it's just that I should put some liquid chlorine in, and then I should be able to maintain?

 

[wireform]

The CYA of 60 isn't a problem except it'll take more chlorine to get the same job done. If you caught it early and keep at it it shouldn't take longer then a few days at most. Rigorously brushing and making sure all the hiding places are covered is your game plan.

 

[Newdude]

+1. You now have a few possible problems. You should have just boosted the FC with liquid chlorine and monitored to see if it held. It's been real high UV lately here and you likely needed to bump the CYA as well. Now there may have been an algae bloom allowed to creep in as well, so Overnight Chlorine Loss Test to ensure you don't need to SLAM Process

If you fail the OCLT you'll want to SLAM at the lowest CYA before raising it after to 70.

 

[poolmedic244]

As I said at the outset, I'm passing the OCLT. I just find that the FC is consistently low and it's ******* me off... I'll add a gallon of liquid to bring it up and see if it stays.

 

[poolmedic244]

The CYA of 60 isn't a problem except it'll take more chlorine to get the same job done. If you caught it early and keep at it it shouldn't take longer then a few days at most. Rigorously brushing and making sure all the hiding places are covered is your game plan.

Are you suggesting that I raise my CYA too?

 

[wireform]

Once you see it stabilize for a few days with OCLT to confirm then you can go up to 70 but be sure all is good first.

 

[Newdude]

We are in the peak season now. We only see the high daily loss for 4-6 weeks, but we're here now. You'll want your CYA at 70 to protect the FC you're making/adding. If it cools off the last two weeks of August (or certainly in September with the shorter days) you can get by with 50 then.

But. Have a current OCLT to prove nothing has happened between the last one which passed and now. We both saw that you had passed OCLT(s) but even one day with low FC since is enough to change the equation and make that one meaningless.

So. Keep your FC up with LC boosts as needed. Pass an OCLT and raise the CYA while keeping extra tabs on the FC until it holds better and you trust the SWG again.

 

[markayash]

Folks -

I've got my Autopilot Digital set to 50-60%. I've been testing the water every day and no matter how hard I try, I can't seem to get the FC above 2 or 2.5. Shouldn't it be producing much more chlorine at this setting threshold? Yes, I've passed the overnight test, and my CYA is somehwere between 50 and 60.

Any ideas? This thing should be going at 30% to achieve these numbers!

Thanks for the advice!
/Joshua.

I had a similar issue and raising my CYA from 50 to 80 alone which raised my FC from 4 to almost 9 with no other changes. I have since turned my SWG down more and keep it around 8ish
One question if you bump your SWG up will the FC go up?

 

[poolmedic244]

I had a similar issue and raising my CYA from 50 to 80 alone which raised my FC from 4 to almost 9 with no other changes. I have since turned my SWG down more and keep it around 8ish
One question if you bump your SWG up will the FC go up?

Probably? I try not to operate it above 60% as that's how you destroy the plates. I have more CYA on hand, but with all the reading that I've done, I still can't get my head around this: 70 will hold more chlorine, sure. But that chlorine is ineffective, so that's the part I don't get...

Regardless, I'll test the water tomorrow to make sure that the LC hit held.

 

[wireform]

That's designed to run @100% and you won't ruin the plates. If the plates get ruined you have other problems.

 

[poolmedic244]

Just keep everyone happy - same reading this morning as last night. OCLT passed. CL reading at 4.5.

I've done the "further reading" on CYA. I've studied the table. I still don't understand this part: If CYA "holds/binds" to chlorine, that makes the chlorine unavailable for sanitizing. What's the difference of a CL reading of 4 with 70 of CYA or 2 with 40 or 50 of CYA? don't you "need more" chlorine to "overcome" the CYA? And just to keep this about the Autopilot - I still don't understand why this thing can't seem to "keep up" at 50-60%!

 

[Newdude]

Just keep everyone happy - same reading this morning as last night. OCLT passed. CL reading at 4.5

OK great !!! We're just looking out for you. It's super easy for me to tell you you need to SLAM and your new FC slam target is 28 because you raised the CYA without an immediate pass of OCLT.

don't you "need more" chlorine to "overcome" the CYA?

You do, and if you look at the chart, it does its best to retain the %'s needed and rounds off the required #s to make it easier.

I still don't understand why this thing can't seem to "keep up" at 50-60%!

Take your daily dose of liquid chlorine and dump it in one shot. You spike the FC and gain 4 FC in a matter of minutes by mixing. It has all day to drift down and still be above minimum. Your SWG uses 12-24 hours to add that same 4 FC. Imagine standing there dripping the gallon one drop every 3 seconds over the course of the day. The pool would lose FC faster during the 4-6 hour mid day than you were adding it. You would gain if it ran overnight, but again, sloooooowly.

By the same token, you may ask why we don't raise the CYA for liquid chlorine to better protect that as well, and the answer is that chlorone burns off as a % and will do so faster at 9 than it does at 3. It's not much faster, but still faster and you'd need more total gallons of LC to get through the summer when there wasn't a need in the first place. That's more cost and more lugging when there was no need because the 30 or 40 FC did just fine the LC way.

 

[poolmedic244]

Take your daily dose of liquid chlorine and dump it in one shot. You spike the FC and gain 4 FC in a matter of minutes by mixing. It has all day to drift down and still be above minimum. Your SWG uses 12-24 hours to add that same 4 FC. Imagine standing there dripping the gallon one drop every 3 seconds over the course of the day. The pool would lose FC faster during the 4-6 hour mid day than you were adding it. You would gain if it ran overnight, but again, sloooooowly.

Okay, so this is starting to make sense, especially since I only run my pump on most days from 6am to 3pm. (we turn it on manually if folks go swimming in the afternoon/evening).

So if I'm reading you right -
I could increase the runtime of the pump to somewhere between 12-24 hours or...
I could raise my CYA to 70 and save on the electricity...

Do I have this right?

It's also worth pointing out that I keep a solar cover on the pool when not in use. I don't know if that protects against UV breakdown or not...but figured I'd call that out.

Thanks for the help. This is uber enlightening...and helpful.

I think the main reason that I'm reticent to raise my CYA is that in the even that I *do* have a problem, it will require a helluvalot more liquid chlorine to beat it.

 

[Newdude]

So if I'm reading you right -
I could increase the runtime of the pump to somewhere between 12-24 hours or...
I could raise my CYA to 70 and save on the electricity...

Do I have this right?

Yes. You need more FC if it's burning off too fast due to UV and not algae. More FC (long term) reduces the cells lifespan by those hours which add up day after day after day.

Or raise the CYA to better protect the FC and keep more of what you produced.

think the main reason that I'm reticent to raise my CYA is that in the even that I *do* have a problem, it will require a helluvalot more liquid chlorine to beat it.

That right there is the irony of the situation. With less CYA and possibly uncontrollable burnoff on particularly high UV days, you're more likely to need the lower SLAM target.

300k+ members fine tuning the science over 15 years wouldn't do you wrong. I'm even your neighbor out east on the Island and can give you dead local experience. We can get away with lower CYA for the bookends of the season, but in the peak/middle, the sun is a force to be reckoned with.

 

[markayash]

If you look at the recommended levels for a SWG even with a CYA of 100 the FC is still 8.

I fought against CYA after battling it before my SwG but after raising mine from 50 to 80 and having to lower my SWg output down to stay in range I was surprised.

I was also trying to save my cell but finally realized saving a little every day was defeating my purpose of buying it