Nope, no ozonator and it's a 500 gallon. Sounds like we're right at target for bather load. With no bather load, I've seen it in the 4ppm range more recently but for quite a while it was 5ppm. What would expected be with no bather load for no ozonator and 500 gallons?
Combined chlorine = 0 but hot tub still has bleach smell
- Thread starter watson524
- Start date
Usually after most bather waste is handled roughly 24 hours after a soak, then subsequent 24-hour periods usually have only a 25% or lower drop in FC level if there is no ozonator. With an ozonator, the drop is 50% or more. Your 4-5 ppm FC from 8-10 ppm FC is closer to a 50% drop.
You might consider on your next water change doing a decontamination/purge using Ahh-Some just in case you've got some biofilms, greases, or other things causing a higher than normal chlorine demand. You might also check your filters to make sure you haven't caught items in the spa that are consuming chlorine.
You might consider on your next water change doing a decontamination/purge using Ahh-Some just in case you've got some biofilms, greases, or other things causing a higher than normal chlorine demand. You might also check your filters to make sure you haven't caught items in the spa that are consuming chlorine.
Ok I might have created some confusion here. So if we're aren't going in it at nite, we test and it's somewhere around 10ppm. I then add enough to raise it to 15ppm so that 24 hours later it's back to 10. So no bather load, goes from 15 to 10 so isn't that a 33% drop? I was figuring bather load was separate from just daily disappearance of chlorine but maybe on the first "day" after bather load, it's all one and I'm double dosing but I don't think so based on my numbers.
Some actual data from my log book:
5/7/15 @ 9:30pm
FC = 11ppm
We weren't going in but I added 3.5oz of 8.25% bleach to raise FC 4.6ppm (targeting that 15 number)
Didn't get to test 5/8/15
5/9/15 @ 8:30am (so 35 hours later)
FC: 9ppm
I added 2.5oz to take it up +3.3ppm since I figured we'd be in that nite so I didn't want to have it so high when I got in
5/9/15 @ 10pm
FC: 12.5ppm
So it really didn't use anything from 8:30am to 10pm the same day
(We then went in for 1 person hour so I added 5.5oz to bump it up 7.3ppm - targetting 20ppm so that 24 hours later I'd have 10 used up in normal daily use and bather load)
Re: our filters, I think we're good there. We take them out and rinse them with the hose once / week and every 4th week they get swapped with the second set of clean filters. We use some Leisure time spray cleaner on them.
Some actual data from my log book:
5/7/15 @ 9:30pm
FC = 11ppm
We weren't going in but I added 3.5oz of 8.25% bleach to raise FC 4.6ppm (targeting that 15 number)
Didn't get to test 5/8/15
5/9/15 @ 8:30am (so 35 hours later)
FC: 9ppm
I added 2.5oz to take it up +3.3ppm since I figured we'd be in that nite so I didn't want to have it so high when I got in
5/9/15 @ 10pm
FC: 12.5ppm
So it really didn't use anything from 8:30am to 10pm the same day
(We then went in for 1 person hour so I added 5.5oz to bump it up 7.3ppm - targetting 20ppm so that 24 hours later I'd have 10 used up in normal daily use and bather load)
Re: our filters, I think we're good there. We take them out and rinse them with the hose once / week and every 4th week they get swapped with the second set of clean filters. We use some Leisure time spray cleaner on them.
Yes, it's a 33% drop since I didn't understand the starting and ending points correctly. So while higher than usual, it's not as bad as I thought. Perhaps the water is remaining hotter or perhaps the bather load is taking more than one day to oxidize.
Just did my test now.
Last nite, 10:15pm FC was 8.5 so I added 4oz to raise it 5.3ppm - we didn't go in so no bather load
Tonite, 10:15pm (exactly 24 hours later) FC is 7.5.
So assuming it went to 13.8ppm after last nite's dose, then it used 6.3ppm in 24 hours which is a lot even for us.
I'm wondering if I should test again after adding the bleach tonite. I planned to add enough to take it to 15 given the target of 10 since that's what we had been doing but I'll add only enough to take it up to 10ppm (2oz = +2.7ppm FC) so that assuming 5ppm loss overnite, it'd be at 5 the next day. But maybe I'll test about 20 minutes after adding once the jet cycle is done to see if I'm actually at 10.2'ish FC.
Not that I don't trust pool math but maybe it's worth checking to see if what pool math says will happen actually happens.
Last nite, 10:15pm FC was 8.5 so I added 4oz to raise it 5.3ppm - we didn't go in so no bather load
Tonite, 10:15pm (exactly 24 hours later) FC is 7.5.
So assuming it went to 13.8ppm after last nite's dose, then it used 6.3ppm in 24 hours which is a lot even for us.
I'm wondering if I should test again after adding the bleach tonite. I planned to add enough to take it to 15 given the target of 10 since that's what we had been doing but I'll add only enough to take it up to 10ppm (2oz = +2.7ppm FC) so that assuming 5ppm loss overnite, it'd be at 5 the next day. But maybe I'll test about 20 minutes after adding once the jet cycle is done to see if I'm actually at 10.2'ish FC.
Not that I don't trust pool math but maybe it's worth checking to see if what pool math says will happen actually happens.
Good idea to test after adding. More about validating the actual water volume in your tub anyway.
Yeah so this is interesting.... I should be a 10.2 FC and I'm at 9.5 so that makes me feel a bit better in that I didn't lose as much as I thought overnite last nite. But that means that the 2oz that should have taken it up 2.7ppm only took it up 2ppm. According to pool math, for 2oz to = 2ppm that means I have 650 gallons of water, which I definitely don't (actually, I feel like I need to add a bit in the next day or so as it's getting a bit low at the neck jet area, tho when we're in it and displace the water it's not an issue).
But since I don't have 650 gallons of water, I'm not entirely sure what to make of the 2oz only raising it 2ppm unless I didn't give it long enough to raise it properly? I figured 15 minutes was sufficient.
But since I don't have 650 gallons of water, I'm not entirely sure what to make of the 2oz only raising it 2ppm unless I didn't give it long enough to raise it properly? I figured 15 minutes was sufficient.
Hmmm. Never a dull moment with pools and hot tubs! Just to be sure. You have 8.25% bleach and that is what is entered in poolmath? Any chance the bleach is a little old and not full strength? If I change it to 6% bleach the number drops to 1.9ppm.
Yep, just double checked. Concentrated label on the outside and in the ingredients, 8.25% sodium hypo. It could be old. What's considered "old" for bleach? I didn't realize it expired. I do have some brand new (a 3 pack I just picked up at Sam's) that I can try with next time and see what that does.
See the table in this post that shows the degradation of 8.25% bleach to be very temperature dependent. The degradation you are seeing is as if the bleach is (9.5/10.2)*8.25% = 7.7% instead of 8.25%. You can see from the table that at 75ºF this can happen after 1 month. If the bleach was stored in or exposed to warmer temperatures, then it would degrade even faster.
Huh, I wouldn't say warmer temps. It's not stored near the baseboard in the laundry room and we have AC in the summer but even at 70deg, after 6 months 8.25% it goes to 6.48% and we've definitely had this over 6 months.
So maybe just pure time is the culprit since the 70deg would be closer to home temp (AC is set at 72). I'll do some repeated tests with a brand new batch that has lived in the garage (somewhat higher heat but much shorter time). Is this the difference between stabilized and non stabilized?
So maybe just pure time is the culprit since the 70deg would be closer to home temp (AC is set at 72). I'll do some repeated tests with a brand new batch that has lived in the garage (somewhat higher heat but much shorter time). Is this the difference between stabilized and non stabilized?
No, this isn't related to chlorine being stabilized. Stabilized chlorine in a pool means there is Cyanuric Acid (CYA) there and the purpose of it is to lessen the degradation of chlorine from sunlight. What is happening with chlorinating liquid or bleach isn't related to sunlight -- exposure to sunlight would have it degrade VERY quickly. Instead, the issue is one of high concentration (in liquid form) and temperature. Every doubling of concentration increases the degradation rate by a factor of 3 or 4. Every 10ºF increase in temperature roughly doubles the degradation rate.
Solid forms of chlorine, such as Trichlor, Dichlor, and Cal-Hypo, degrade much more slowly mostly because they are kept dry, but they do degrade as a function of temperature. Nevertheless, such products typically last for a year or more unless stored in hotter environments.
Solid forms of chlorine, such as Trichlor, Dichlor, and Cal-Hypo, degrade much more slowly mostly because they are kept dry, but they do degrade as a function of temperature. Nevertheless, such products typically last for a year or more unless stored in hotter environments.
Wanted to revive this for a bit. A few posts up I added an amount of bleach expected to raise the FC by 2.7ppm and it only went up by 2ppm after testing. As I'm draining my tub today and cleaning it, I happened to see a spec sheet in the packet that says "water capactiy (average fill)" is 500 gallons (what I've been using in pool math) but then it says "water capacity (spa volume) 580 gallons". We keep it to a level right under the pillows when we're not in it (I like my shoulders totally covered when I'm in) so I'm wondering if we're on the high side and I should use the higher number for pool math. That might explain why the FC didn't go up as much as I expected 20 minutes after dosing.
It could be that or the bleach could be slightly degraded or there could be some measurement error. If you find it consistently off, even with fresh bleach bottles, then yes you can adjust the volume assumption.
I won't have it for this fill but for next fill, I ordered a meter gizmo to go on the hose (I've wanted one anyway for another purpose) so that should help solve this once and for all if I haven't by then.
ewkearns
0
Yes, we did. Have towels or magic erasers ready, if the *whatever* dries on the tub, it turns to concrete...
Yeah I used some Spray 9 to coax it along as needed and then rinsed well before next fill and we are draining that as we speak.