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Week 1 Challenges


FightinTxAg
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I got a used 400 gal Jacuzzi Model 340 (~10 years old) off Craigslist.

I started off doing a decon last Wed. I added an entire 182 oz jug of bleach, which should've put FC up over 200ppm. I ran the tub with high jets for about an hour, opening and closing the air controls every 10-15 minutes or so. Then, I turned it down to circulation, and let it run overnight.

Thurs:

Drained, installed a new filter, filled and tested for baseline.

CH = 190; TA = 160; pH = 7.9; FC = 0

*I added 24oz of Borax to get my borates up to 50.

*I added 12oz of Acid to lower pH, TA, and balance the Borax.

*I added 10 oz of Bleach (~12ppm FC).

*I added 1 oz HTH Stabilizer/Conditioner.

Friday:

I was surprised with all the stuff I added, everything seemed to zero in on what I was aiming for. Beginner's luck, I guess.

TA = 80; CYA = just under 30; pH = 7.5; FC = 4.5

*I added 4 oz Bleach (~5ppm FC).

*We were kind of excited, and it was Friday night. So we invited some friends over, and there were probably 8 bather-hours spent in the tub.

*I added 8oz Bleach afterward (~10ppm FC).

Saturday:

Crap! FC went to zero. I knew I should've tested instead of just throwing 8oz of bleach at it and assuming that'd be good.

pH = 7.9; FC = 0

*I added 20 oz Bleach (~24ppm FC).

*I added 2 oz of Acid.

Sunday:

I wanted to check to see if TA had moved since the acid and aerating Friday night. I also wanted to make sure my CYA hadn't depleted when the FC was zero:

TA = 40; CYA = just under 30; pH = 6.8; FC = 4; CC = .5

*I added 4 oz of Baking Soda to raise the TA.

*I added 2 oz of Borax to raise the pH. So now my Borates must = 54.

*Since I still had FC left, I thought it'd be safe for the wife and I to have a quick soak. The two of us were in the tub maybe 20 min, so <1 bather-hour.

*I added 8 oz of Bleach after the soak (~10ppm FC).

Monday:

Crap! FC back to zero, and I overshot the pH.

CH = 170; TA = 90; pH = 8.0; FC = 0

*I added 16 oz of Bleach (~20ppm FC)

*I added 1 oz of Acid.

*I added 2 oz of HTH Defoamer because I noticed foam during the Sunday night soak.

An hour later:

pH = 7.5; FC = 13.5

*I was concerned that a third of FC was used up in an hour. So I added another 4oz (~5ppm FC) for good measure.

I think at this point, I have to just stay on top of pH and TA, and keep shocking to an FC above 10ppm and not use the tub until FC demand is 50% or less. Is that the right track?

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I got a used 400 gal Jacuzzi Model 340 (~10 years old) off Craigslist.

I started off doing a decon last Wed. I added an entire 182 oz jug of bleach, which should've put FC up over 200ppm. I ran the tub with high jets for about an hour, opening and closing the air controls every 10-15 minutes or so. Then, I turned it down to circulation, and let it run overnight.

Thurs:

Drained, installed a new filter, filled and tested for baseline.

CH = 190; TA = 160; pH = 7.9; FC = 0

*I added 24oz of Borax to get my borates up to 50.

*I added 12oz of Acid to lower pH, TA, and balance the Borax.

*I added 10 oz of Bleach (~12ppm FC).

*I added 1 oz HTH Stabilizer/Conditioner.

Friday:

I was surprised with all the stuff I added, everything seemed to zero in on what I was aiming for. Beginner's luck, I guess.

TA = 80; CYA = just under 30; pH = 7.5; FC = 4.5

*I added 4 oz Bleach (~5ppm FC).

*We were kind of excited, and it was Friday night. So we invited some friends over, and there were probably 8 bather-hours spent in the tub.

*I added 8oz Bleach afterward (~10ppm FC).

Saturday:

Crap! FC went to zero. I knew I should've tested instead of just throwing 8oz of bleach at it and assuming that'd be good.

pH = 7.9; FC = 0

*I added 20 oz Bleach (~24ppm FC).

*I added 2 oz of Acid.

Sunday:

I wanted to check to see if TA had moved since the acid and aerating Friday night. I also wanted to make sure my CYA hadn't depleted when the FC was zero:

TA = 40; CYA = just under 30; pH = 6.8; FC = 4; CC = .5

*I added 4 oz of Baking Soda to raise the TA.

*I added 2 oz of Borax to raise the pH. So now my Borates must = 54.

*Since I still had FC left, I thought it'd be safe for the wife and I to have a quick soak. The two of us were in the tub maybe 20 min, so <1 bather-hour.

*I added 8 oz of Bleach after the soak (~10ppm FC).

Monday:

Crap! FC back to zero, and I overshot the pH.

CH = 170; TA = 90; pH = 8.0; FC = 0

*I added 16 oz of Bleach (~20ppm FC)

*I added 1 oz of Acid.

*I added 2 oz of HTH Defoamer because I noticed foam during the Sunday night soak.

An hour later:

pH = 7.5; FC = 13.5

*I was concerned that a third of FC was used up in an hour. So I added another 4oz (~5ppm FC) for good measure.

I think at this point, I have to just stay on top of pH and TA, and keep shocking to an FC above 10ppm and not use the tub until FC demand is 50% or less. Is that the right track?

You seem to have a very good handle on your situation. My recommendation for changing ph & TA would be to calculate the amount of chemicals you are to add and then halve it. Add that and recheck in an hour or so. Then calculate and half it again....keep doing that until you hit your mark. That way you don't overshoot. which is utterly frustrating.

As to using so much chlorine, you mentioned foam...which means you must be getting in with suits and clothes and such. I have noticed our CD going up dramatically when we have fabrics in the tub.

To keep your CD down a you may try adding MPS just before the soak and then add your bleach after. MPS really helps your chlorine out.

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Thanks, Bart!

I was kinda hoping to get by without MPS at first, trying to keep things simple as I start out, and avoid adding another variable. But, if I'm going to have trouble keeping the FC up without throwing a little MPS in, then I guess I'll have to abandon that.

Question: Is there a linear or quadratic or some higher order equation that relates FC loss to time? I'm curious if there might be a way to figure out FC Demand in a time period less than 24 hours.

For instance, if the relationship were linear (which I doubt), then the equation would look like:

A(t) + B = FC Loss

Then, if 10% of FC was used in 2 hours, and 17% was used in 4 hours, you could solve for FC Demand, and have it figured out in 4 hours instead of 24.

A(2) + B = .10

A(2) = .10 - B

A = ( .10 - B ) / 2

A(4) + B = .17

[( .10 - B ) / 2](4) + B = .17

B = .03

A = .035

FC Demand is FC Loss at t = 24. So...

A(24) + B = .035(24) + .03 = 87%

Then, knowing you were on track for an 87% FC Demand, you could add more chlorine. And, then refigure your FC Demand again within a couple hours. This would let you get a high FC Demand problem resolved in a matter of hours instead of days.

If the equation is quadratic, or something even higher, you might need several data points, over a couple hours and do a best fit trendline in Excel to find the proper equation. Then, you could use that to determine FC Demand at the 24 hour mark.

But, you'd need to know the order of the equation that relates FC Demand to Time to do this.

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Tuesday:

I went home at lunch and checked. So this is about 12 hours after I added 4oz Bleach (~5ppm FC) to the tub when it already measured 13.5ppm FC.

TA = 70; pH = 7.5; FC = 8.5; CC = 1.5

*So FC was down from what should've been ~18.5ppm to 8.5ppm in just 12 hours.

*I added another 8oz (10ppm FC) of Bleach.

I added 16oz of bleach on last night, and that should've raise FC about 19ppm.

If an hour later, FC was just 13.5ppm, what does that mean? Does that mean there was a lot of ammonia/urea that combined quickly? Does that mean I probably have a lot of chloramine in the tub now to oxidize?

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Tuesday:

I went home at lunch and checked. So this is about 12 hours after I added 4oz Bleach (~5ppm FC) to the tub when it already measured 13.5ppm FC.

TA = 70; pH = 7.5; FC = 8.5; CC = 1.5

*So FC was down from what should've been ~18.5ppm to 8.5ppm in just 12 hours.

*I added another 8oz (10ppm FC) of Bleach.

I added 16oz of bleach on last night, and that should've raise FC about 19ppm.

If an hour later, FC was just 13.5ppm, what does that mean? Does that mean there was a lot of ammonia/urea that combined quickly? Does that mean I probably have a lot of chloramine in the tub now to oxidize?

I think you have something going on in your tub, something dirty.

I would keep it at super shock levels for a few days at least and keep checking it.

I would also start using MPS to start lowering your CC more quickly and assist your chlorine.

I read your post above the last, and honestly just don't have the brainpower left tonight to give you an answer worthy of the question...tough day at the bike shop.

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I think you have something going on in your tub, something dirty.

I would keep it at super shock levels for a few days at least and keep checking it.

I would also start using MPS to start lowering your CC more quickly and assist your chlorine.

Yeah, that's what I'm beginning to think too. The guy I bought the tub from went out of town the week before I got it. So he may have had it full for a week with no chemical attention at all.

I thought a full 182 oz jug of bleach, overnight decon, and new filter would take care of any issues, but I'm beginning to think maybe not. Maybe there's some biofilm or something that's going to take a lot of FC and time to resolve.

At 10pm tonight, I had:

TA = 80; pH = 7.6; FC = 9; CC = 1.0

Remember at lunchtime I had 8.5 FC and added 8 oz of Bleach (so ~10ppm FC). That means, I should've had about 18.5 FC.

So again, I must've lost ~50% of FC in about 12 hours.

Well, with a measured residual of 9ppm FC, I figured it would be ok to have a soak. So, we spent about 1.5 bather-hours in the tub. Afterward, I thought I'd go ahead and shock the heck out of it. I added 40 oz of bleach (should be ~50ppm FC). I'll see what I've got left tomorrow. I might wait a full 24 hours to get a real read on FC Demand.

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I think you have something going on in your tub, something dirty.

I would keep it at super shock levels for a few days at least and keep checking it.

I would also start using MPS to start lowering your CC more quickly and assist your chlorine.

Yeah, that's what I'm beginning to think too. The guy I bought the tub from went out of town the week before I got it. So he may have had it full for a week with no chemical attention at all.

I thought a full 182 oz jug of bleach, overnight decon, and new filter would take care of any issues, but I'm beginning to think maybe not. Maybe there's some biofilm or something that's going to take a lot of FC and time to resolve.

At 10pm tonight, I had:

TA = 80; pH = 7.6; FC = 9; CC = 1.0

Remember at lunchtime I had 8.5 FC and added 8 oz of Bleach (so ~10ppm FC). That means, I should've had about 18.5 FC.

So again, I must've lost ~50% of FC in about 12 hours.

Well, with a measured residual of 9ppm FC, I figured it would be ok to have a soak. So, we spent about 1.5 bather-hours in the tub. Afterward, I thought I'd go ahead and shock the heck out of it. I added 40 oz of bleach (should be ~50ppm FC). I'll see what I've got left tomorrow. I might wait a full 24 hours to get a real read on FC Demand.

I would do a 24 hour CD reading just to be sure. As your sample time increases your margin of error decreases.

Have you changed/cleaned the filters of the tub?

Dirty filters can contribute to CD.

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