Winter refill? Necessary?

[cubsno1]

I refilled my spa about a month ago before it got too cold here. I got the water balanced and started on my dichlor for CYA and chlorine. I have since neglected maintenance on it, but it has also not been during this time (or at all since the refill). Should this water still be okay to re-balance (if necessary) and "shock" or is it likely that I need to dump and refill it again?

 

[Richard320]

Test it. It doesn't wear out. Algae also doesn't grow much when the water gets cold, so even if the FC is low, the water will probably still be clear.

 

[cubsno1]

Thanks I'll check it. The water hasn't been cold.. I've kept it on and at it's normal temperature, but like I said it hasn't been used and the lid has been closed.

I'll run through all the tests and see where it's at before proceeding.

 

[chem geek]

If there's nothing visibly wrong such as dull/cloudy water or biofilms on spa surfaces, then the main test is to see the 24-hour chlorine loss rate with no bather load. With no ozonator and fairly new water, the loss should be around 25% at typical hot spa temperatures. With an ozonator or with older water (i.e. a spa that's been used a lot before changing the water) it might be 50% or more loss. If the loss you measure is significantly higher than this, then you've got something growing in your spa and may need to decontaminate it.

 

[cubsno1]

When doing the chlorine loss test should I bring it to 10ppm and then check it in 24 hours? Or at what level do I start the test?

 

[chem geek]

You can set the chlorine to it's normal daily maintenance level which is probably in the 2-4 ppm range. For an accurate loss test, use a 25 ml sample size for the FAS-DPD test so that you get a 0.2 ppm resolution. This is one of the few times when such higher accuracy is useful. The problem with setting the FC too high is that it will overcome some of the CYA so have more than proportionally more active chlorine and that can throw off the loss rate having it be higher and therefore fooling you.

 

[cubsno1]

Ok, perfect I will give that a try and post back.

 

[cubsno1]

Test results:

PH - 7.5
TA - 110
CH - 220
CYA - 25
FC - 0
CC - < 1 (.4'ish)

300 gal spa, 100 degrees. Pool calculator says .3oz dichlor will raise FC by 4.1 ppm and CYA by 3.8 ppm.

Going to go ahead and add that, then check it tomorrow at about this time to see where it is. Water was clear and nothing floating or scummy about it so hopefully it will be okay.

 

[chem geek]

Well, it's not every good to have the FC get to 0. It only takes some number of hours for biofilm to form to the point where even then dosing with chlorine won't get rid of it. You should probably test the chlorine level about 15 minutes after you've added it, assuming your circulation pump is on in your spa.

 

[cubsno1]

Sorry chem geek, I didn't get your message until this morning. I just went out to check it this afternoon and it's down to about 1.4PPM from 4 about 24 hours ago. Could this still be salvageable or am I emptying?

 

[chem geek]

That's a 65% loss over 24 hours. Do you have an ozonator? If you do and it is strong or on a lot of the time, then one could have that kind of loss. If you don't have an ozonator, then that's unusually high and you can try shocking the water to see if it helps.

 

[cubsno1]

Sounds good... on 12/24 at about 10PM I ran it up to about 20ppm with 6% bleach. I'll check it tonight and see where it's sitting.

 

[cubsno1]

Checked it and it was down to 2PPM. Ran it back up to 20PPM, will check it again tonight and see if it's getting any better or still losing.

 

[chem geek]

You're losing an awful lot of chlorine without any bather load. If this keeps up, then you may need to decontaminate your spa because something in it is consuming a lot of chlorine.

 

[cubsno1]

I agree with you.. but at 10 degrees outside, chances are pretty good if I empty it I won't be filling it back up. Thanks for your help on this.. I will give it a few more doses and if it doesn't stabilize I'll decontaminate and dump.