Losing too much FC?

[urville]

I dont think i understand bather load?

This is an inflatable, it doesnt remove water surface debris from soaks super well. When I've added chlorine, I get alot of foam, which I skim off the surface. The water looks clear, there is just some dead skin after soaks. Started reading about acceptable FC loss, grew concerned, shocked tub. Other parameters have not changed, water is still balanced.

7/14 tub at 8pm is 3.5 FC

7/15 Next morning tub is at 2.5 Still using dichlor to raise CYA at this point Raise to 4 FC via dichlor Soaked 45 minutes midday 2 people bathed .5 FC When they got out Added dichlor to raise FC to 4 8:33 PM Tub is at 2 FC Dichlor raised to 4 ppm 2 people bathed soak for 45 minutes 2.5 FC when they got out Dichlor to raise FC to 4

7/16 8:45 PM 1 FC Dichlor to 4ppm 2 people soak bathed 30 minutes tested 3 FC Dichlor to 6 FC

7/18 7:30A 1 FC Dichlor to 5.5 FC 9:00 PM - 3 FC and .5 CC Switch to bleach CYA now 30, confirmed via test Add bleach to 7 FC

7/19 - 11:30 pm 2 FC - .5 CC Up FC to 12 via bleach

7/20 11:30pm 5FC

 

[jeffchap]

You may have a nascent algae bloom. You are not keeping your FC consistently at a high enough level to kill it off. You need to perform a SLAM. Raise your FC to 14 and test as frequently as possible -- hourly if you can, and add bleach to maintain that level. Never let it fall below 12, or you will be losing ground.

Continue until your FC loss overnight is 1 or less, CC measures .5 or less, and your water is perfectly clear.

You can continue to swim as long as you add bleach to keep FC above 12.

 

[urville]

You may have a nascent algae bloom. You are not keeping your FC consistently at a high enough level to kill it off. You need to perform a SLAM. Raise your FC to 14 and test as frequently as possible -- hourly if you can, and add bleach to maintain that level. Never let it fall below 12, or you will be losing ground.

Continue until your FC loss overnight is 1 or less, CC measures .5 or less, and your water is perfectly clear.

You can continue to swim as long as you add bleach to keep FC above 12.

Overnight last night, as you can see from the chart for last night I had 5 FC. So, this morning about 7:40 I had 4.5 FC still and 1 CC. I am about to go out and test again.

Do you think i still need to SLAM? I did not add chlorine this morning as the small loss was encouraging. Maybe I will find a terrible story when I go out here in a minute.

 

[jeffchap]

It wouldn't hurt, just to be sure. A day or two should be plenty.

 

[urville]

It wouldn't hurt, just to be sure. A day or two should be plenty.

Just got back in from testing and It went from 4.5 FC this morning to 3.5 just now and only .5 CC

It seems like I killed whatever it was, does it not? I mean I can SLAM it more... I'm not sure we feel comfortable using it that high of FC, but only half a PPM loss overnight and only 1ppm over the day seems like a good sign.

If I had to guess it was from me adding chlorine up to only 4ppm after they soaked in it.

Pretty sure this is where I messed up. I should have been shooting for 7ppm after the soak. Though I dont get the reference to "amounts independent of spa volume" unless that means the 7ppm.

Also, the 7 ppm FC in 350 gallons per person per hour of soaking guideline (at 104F) isn't in the Pool School either. This translates into amounts that are independent of spa volume of 3-1/2 teaspoons of Dichlor or 5 fluid ounces of 6% bleach or 7 teaspoons of MPS non-chlorine shock. These are conservative amounts of chlorine needed to oxidize bather waste (mostly ammonia/urea from sweat/urine). The biggest mistake most spa users make is not using enough oxidizer in their spas, especially if such spas are more heavily used.

 

[mknauss]

What spec is this pool /tub? If small volume, drain and refill. That needs to be done every few months with a hot tub or stand alone spa anyway.

Fill out your signature with some specs to helps us out -- Pool School - Read This BEFORE You Post

 

[urville]

What spec is this pool /tub? If small volume, drain and refill. That needs to be done every few months with a hot tub or stand alone spa anyway.

Fill out your signature with some specs to helps us out -- Pool School - Read This BEFORE You Post

It's vinyl. It's 210 gallons. It has been up for just over 8 days. Drain already?

My water tests balanced.
7.4 PH - 130 CH - 50 Borate - 35 CYA - 50 ALK - Temp 104F

Added bleach to raise the 3.5 FC to 7 FC last night
Woke up and tested about 10 minutes ago at 5.7 FC and .7 CC thats a loss of about 1.5

 

[mknauss]

At 210 gallons that is almost like a bath tub! I think you are going to see swings in your test data because of that low volume. It would take a teaspoon more or less of chlorine to significantly effect your ppm.

Take care.

 

[urville]

What does that mean?

 

[dsmith99]

Maintain your FC a bit higher, it's still safe to use all the way up to 12 because of the CYA level.

You should expect to see higher FC use and CC building up a bit after the tub is used because it is such a small amount of water. After two users for about a half hour I add about 3-4 oz of bleach in my 330 gallons which takes it to about 10ppm or so. Leaving the top open for a while can also help the CC off gas and leave the tub. If you go a day or two without use you will still need to dose to maintain the FC level.

Pool procedures don't always apply well to a hot tub because of the hot water and the small volume. After use of the tub it will continue to consume FC for hours killing off bacteria because everything is hundreds of times more concentrated than it would be in a pool, that makes an OCLT not really practical. With the top covered up tight to maintain the heat, it also blocks the sun and slows the release of CC. Algae is not really a problem in a tub because it's covered most of the time and gets little sun exposure.

You can do a few things to minimize problems, rinse off in the shower prior to using the tub to get rid of perfumes, deodorants or other contaminants. Wash long hair or put it up to keep hair products out of the water. Use suits dedicated to the hot tub and don't run them through the laundry, just rinse them out in the sink to keep residual soap out of the tub.

 

[Akathisia]

I review this several times a year and always find something new or something I forgot: How do I use Chlorine in my Spa (or pool)?)

 

[urville]

I review this several times a year and always find something new or something I forgot: How do I use Chlorine in my Spa (or pool)?)

Thats all I have been doing is reading and rereading that thing, although I must say.... Theres alot missing from that document from a noob perspective. Alot of it is things that are "assumed to be known" that shouldnt be.