Do I use the same math on the (inflatable) hot tub that I have been using on the pool for years? And a few other questions..

Skenn81

Well-known member
Apr 23, 2018
218
Florida
On a hot tub can I be using liquid CL like I do on my pool? On the pool I do just liquid CL once the stabilizer is adjusted and it happily keeps going, I test and check and add and use the calculator and we keep swimming all season long.

Came into possession of an inflatable hot tub for Christmas. Despite it being a hot tub do I use the same FC/CYA chart I have been using for years or is there a different metric I am supposed to be basing this off of since it's a hot tub and not a pool? I had it up at SLAM and then we just used it since we wanted to get in during the cold nights. Went out this morning. CYA (60) and pH (7.2) holding steady, CL is at an absolute 0. 0 as in adding the R-0870 powder didn't even change the water color sample in the slightest. I thought it was broken so tested the pool again, its fine, the hot tub is not. Added CL for SLAM again since I guess I either didn't finish the first one (I didn't check because we just wanted to get in) and its so small its not like it takes a lot to get it from 0 to SLAM, under 8 ounces.

I have been using this one: Chlorine / CYA Chart - Trouble Free Pool

For the calc I just scaled everything back from 15,000 to 210 gallons.

I also read this:

I have my CYA at the level I want so liquid is what it says to use, just like my pool. pH is also adjusted. I wont be using dichlor tabs as it will just make the CYA even higher.

Does CL and such hold like it does in a pool or because it's warmer than a pool it will be a lot harder to keep? Also testing, should I be testing this a lot more often than my pool, which I was doing once every two or three days once I got into a pattern? Also, hot tub doesn't run 24/7 - when adding chemicals can I let it run for a couple of hours then turn it off? We only run it when we are going to heat it up.

We are only going to keep the hot tub up for a few months then deflate and put away until next winter. I want to keep this going until February so figure I will learn what I am doing so I can have an easier time next year.

I know I could drain it and restart and then heat it back up, but I don't want to do that, I want the challenge of figuring the chemicals out and learning from this so I can know how to do it better next year. It will give me something to do during this week since I wont really be working until new years.
 

Mdragger88

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Jun 1, 2018
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Hernando, Ms
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Same math 👍🏻
Here’s the sticky on using chlorine in the spa 👇
You just want cya to 30ppm & ta around 50.
Every time u use the tub take it to slam level for your cya so you can ensure you have some residual left before the next soak. Test before & after using to get a feel for how much gets consumed w/ & w/out use. Never let it go to 0. Bather/organic load is much higher in a small tub vs pool. 1 person’s 30 minute soak can use up 2-4 ppm fc. YMMV. More people/time = more bleach 😊
A cya of 60 is too much & will make your bleach less effective- it’s covered so the cya is just there to make the fc less harsh & allow u a higher fc level- not for sunscreen.
Your will still adhere to the FC/CYA Chart
 

Mdragger88

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Jun 1, 2018
3,162
Hernando, Ms
Pool Size
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SWG Type
Intex Krystal Clear
Also it takes more energy to “heat it up” than it does for it to just maintain temp & It has a built in filter cycle that u are killing by turning it off. U could meet in the middle by turning it down a few degrees when not in use. Which will still allow the filter operation
 

Skenn81

Well-known member
Apr 23, 2018
218
Florida
I'm all jacked up then with the CYA at 60. I did that because it's always what I kept my pool at, I would have it higher because the sun would constantly burn the CYA down and every few months I would need to raise it up again. I once tried keeping it lower but the Florida sun tricked me and I ended up with CYA of almost 0.

Is this part recoverable or do I need to really start over and try to get CYA to 30? I dont mind maintaining a higher CL to balance out the 60 I am at now though if all I need to do is just use the higher numbers on the chart.

I will need to adjust TA though, calcium hardness as well once I get things back in order. I need some calcium hardener anyway so I might as well use this as an excuse to go tot he store and pick some up.


Bather/organic load is much higher in a small tub vs pool. 1 person’s 30 minute soak can use up 2-4 ppm fc. YMMV. More people/time = more bleach 😊

Okay that's good to know, I didn't check it when we used it the few times, I didn't really think about how we might be using a lot more sitting in there compared to in the big pool.



A cya of 60 is too much & will make your bleach less effective- it’s covered so the cya is just there to make the fc less harsh & allow u a higher fc level- not for sunscreen.

Oh, so its a different way of thinking about it? I always said CYA is like sunscreen for a pool, and having it higher with the Florida sun let me keep it going longer. You are right though, the hot tub is covered all day long and it's not being used in direct summer heat. So the CYA is serving a different kind of purpose in the hot tub? It's not keeping the sun from burning the CL off so it's there to keep the CL in the water?
 

Mdragger88

Bronze Supporter
Jun 1, 2018
3,162
Hernando, Ms
Pool Size
26000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Intex Krystal Clear
you can just drain 1/2 the water. Do this before u add anything else as to not waste it. If your ch is 100 you can probably just leave it alone. Mine is 50 sometimes i add to 150 sometimes I don’t- I have never noticed a difference. Some people notice foaming w/ lower ch . If u use ch for your pool it is fine for your tub. “Spa” chems are just in over priced small packages. The only one i buy is 99%dichlor @ Walmart. It’s $10 & 1 lb. lasted me 2 yrs. 🤣
Cya binds some of your chlorine that is why when u have more cya u need more chlorine to remain sanitaryFC/CYA Chart
If u notice its also called “conditioner” on some packages.
Having a cya of 30 allows you to have a fc target of 6 & a slam/shock level of 12 w/ out being too harsh & gives it room to drop w/ bather load without going to zero.
Whereas if u had no cya anything above 3 would be to harsh for use & would also be depleted before your soak was done. 🤢
@ a cya of 60 you have a target of 9ppm & a shock level of 24ppm which is hard to maintain & kind of a waste of bleach.
It will probably only take about 30 minutes to exchange 1/2 the water.
 

Skenn81

Well-known member
Apr 23, 2018
218
Florida
you can just drain 1/2 the water.

Okay good point, I will take this approach and report back later, drain half, fill half, filter for a bit, then recheck CYA after an hour or so? CYA and CL are my primary here. pH was okay, TA and CH I haven't made it to yet because of the current issue.

Also it takes more energy to “heat it up” than it does for it to just maintain temp & It has a built in filter cycle that u are killing by turning it off. U could meet in the middle by turning it down a few degrees when not in use. Which will still allow the filter operation

What is a good "maintenance mode" temperature for a hot tub? It's 104 at peak for the cold nights. I dont think this one has much of a filter cycle other than it's on for 24 hours or it's off. It's not a very advanced unit, basically a big inflatable tube with a heater and filter attached to it. Intex brand. I didn't see a way for the filter to actually cycle other than me going out there and pushing the filter button.
 

Mdragger88

Bronze Supporter
Jun 1, 2018
3,162
Hernando, Ms
Pool Size
26000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Intex Krystal Clear
Here’s the manual 👇
It indicates that filter mode runs when the heater is activated. So as it maintains temp it will filter. It might be a good idea to get an extra filter so you can just swap them out & always have a clean one ready to go. Most error codes people have issues with on these tubs are related to dirty filters. As they aren’t very large & get dirty quickly especially when people don’t maintain very good chemistry since they often don’t see it as a “real spa” however it should be treated the same.
 

Skenn81

Well-known member
Apr 23, 2018
218
Florida
50% drained and refilled. I think the CYA is closer to 30 now but I might want to raise it a bit. I don't have dichlor tabs but I do have standard granular stabilizer. If I do the calculator and raise 30 to 35 on a 210 gallon tub it says I need about half a teaspoon. I can add that and check. The reason I want to is that even at the 30 mark the test water was very cloudy but I could still ever so slightly see the black dot. That's fine, right? I am going to try to keep the FC at 12 for a while to slam it around.

Adding chemicals to something this small is a lot harder than the big pool. Using the big 2.5 gallon jugs of chlorine to pour out 3 ounces of liquid into basically a tablespoon measuring spoon is rough. What does everyone do to measure such small quantities?
 

Mdragger88

Bronze Supporter
Jun 1, 2018
3,162
Hernando, Ms
Pool Size
26000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Intex Krystal Clear
Between 20 & 30 u can call it 30 & move on. Don’t sweat it.
You may need to top it up with dichlor every couple weeks since its a small tub & u will have splashout & need to replenish water.
for measuring dry things or ma i use this 👇
i just google oz to tsp conversions
C4ECAFB7-F244-4461-89F1-4F84028312A2.jpeg
For bleach i use a measuring cup or a mason jar w/ oz - i also store it in a smaller easier to pour bleach jug near my hot tub
 

Skenn81

Well-known member
Apr 23, 2018
218
Florida
How do dichlor tabs work? They are the pucks, right? How much do they weigh or what size are they? I see the calc at the bottom has a drop down option for them, never used that before.

Is there harm in going above SLAM levels while getting it back up and running? 3 oz is hard to measure so I can just put extra in and call it a day. Half a cup is 4oz and easier to measure than a buch of tablespoons.
 

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Mdragger88

Bronze Supporter
Jun 1, 2018
3,162
Hernando, Ms
Pool Size
26000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Intex Krystal Clear
Dichlor is granules. It is acidic so remember to consider its effects on ph when adding.
U can use “effects of adding” in the hamburger menu of PoolMath to see the impact of your additions before use of any chemical.
With bleach i use my measuring cup/ mason jar - it has 1 oz incriments
Going over slam regularly isn’t advisable or necessary but eyeballing 3oz is fine.
 

Skenn81

Well-known member
Apr 23, 2018
218
Florida
Dichlor is granules.

This is what I have, it's a granule based product:

rGzKHJn.jpg


tCFsiRD.jpg


This is just stabilizer, nothing else. I use the liquid bleach only. Do I need dichlor or will my combo attack work like it has been in the pool?

We are finishing up day 1 now of the hot tub reboot. So far looking clear. Continuing on with the slam every 4 or so hours because why not. Never got the calcium stuff so I will be doing that today. pH was through the roof when I refilled, beyond 8, was at a level I couldn't even register so I added acid in to get it down to 7.2, but during SLAM I know I can't really check it.

I have it turned up on the heat as well, I did read the manual and saw the filter runs when heating, but then it also stays on 24 hours after heating so I don't think it will ever turn off. Just need to get it through NYE and New Years Day and I can calm down for a while.
 

jseyfert3

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Came into possession of an inflatable hot tub for Christmas. Despite it being a hot tub do I use the same FC/CYA chart I have been using for years or is there a different metric I am supposed to be basing this off of since it's a hot tub and not a pool? I had it up at SLAM and then we just used it since we wanted to get in during the cold nights. Went out this morning. CYA (60) and pH (7.2) holding steady, CL is at an absolute 0. 0 as in adding the R-0870 powder didn't even change the water color sample in the slightest. I thought it was broken so tested the pool again, its fine, the hot tub is not. Added CL for SLAM again since I guess I either didn't finish the first one (I didn't check because we just wanted to get in) and its so small its not like it takes a lot to get it from 0 to SLAM, under 8 ounces.
As has been covered bather load is very high in a spa relative to water volume. Usually I bring to SLAM levels before we get in for long soaks and add additional chlorine when we get out. It's often 2-3 of us for many hours, the FC is usually 0 well before we even get out!

Does CL and such hold like it does in a pool or because it's warmer than a pool it will be a lot harder to keep? Also testing, should I be testing this a lot more often than my pool, which I was doing once every two or three days once I got into a pattern? Also, hot tub doesn't run 24/7 - when adding chemicals can I let it run for a couple of hours then turn it off? We only run it when we are going to heat it up.
Yes, test more often, especially after use. You don't want it to let it drop to zero if possible. After a use is especially critical to test and adjust FC, as it takes days sometimes to burn off the waste from a long soak.

You can turn the heat down but don't turn the filter off.

A cya of 60 is too much & will make your bleach less effective- it’s covered so the cya is just there to make the fc less harsh & allow u a higher fc level- not for sunscreen.
Not if the FC levels are increased. That's why we have the FC/CYA chart, if you maintain the appropriate FC level it's just as effective at any CYA level. The issues stem when people allow CYA to build up and do not increase the FC levels appropriately. There's nothing "wrong" that I am aware of with running a spa at a CYA of 60 if FC is held at the appropriate level. However you will need to hold the FC levels higher which may cause some amount of additional FC loss and more testing reagents to test a higher FC level.

Also it takes more energy to “heat it up” than it does for it to just maintain temp & It has a built in filter cycle that u are killing by turning it off. U could meet in the middle by turning it down a few degrees when not in use. Which will still allow the filter operation
Respectfully, it does not. This is a common myth. Turning down the temp between uses will always result in less energy usage. Heat loss is proportional to the temp differential between the water temp and the air temp. The bigger this difference, that faster the heat loss. Turning down the temp allows this difference to be less, which means heat loss is lower. The energy used to reheat the tub will be less than if the tub was maintained at the high temp continuously.

Lower heat will also slow FC and CYA loss due to heat.

That said, I leave my tub at temp year round, as I want it ready to use whenever I want, and I don't want to wait hours for it to heat up.

How do dichlor tabs work? They are the pucks, right? How much do they weigh or what size are they? I see the calc at the bottom has a drop down option for them, never used that before.
This is just stabilizer, nothing else. I use the liquid bleach only. Do I need dichlor or will my combo attack work like it has been in the pool?
Dichlor is generally powder. It adds chlorine and CYA, and is acidic. You don't need it if you have straight CYA, as you do. Just use that as needed to maintain CYA as needed.

Is there harm in going above SLAM levels while getting it back up and running? 3 oz is hard to measure so I can just put extra in and call it a day. Half a cup is 4oz and easier to measure than a buch of tablespoons.
I got these little 8 oz graduated measuring cups for my spa. Works great for measuring out any amount of oz up to 8. Perhaps you could find something on Amazon or at your local farm supply store?
 
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Skenn81

Well-known member
Apr 23, 2018
218
Florida
First off, wow, thanks for the response! So much to take in. I will respond to what I can here..

Also for a general update, I am going to stop with the CL for now. The reading is currently way overboard, 20 drops in and it still didnt turn from red to clear so going to let that fade. Also because of the ultra high FC I can't get a CH reading, so I will try that once things calm down as well. I think anything in there right now should be dead, I may have gone overboard with the SLAM. Picked up a 50lb bag of calcium hardener so I am ready to go once my numbers start dropping.

I got these little 8 oz graduated measuring cups for my spa. Works great for measuring out any amount of oz up to 8. Perhaps you could find something on Amazon or at your local farm supply store?

Going to get one of those at Tractor Supply. They were supposed to have some in stock but didn't so they are going to get me one. Would rather go there than Amazon if I can. I got the 32 oz one which has single oz markers for now which will work.

As has been covered bather load is very high in a spa relative to water volume. Usually I bring to SLAM levels before we get in for long soaks and add additional chlorine when we get out. It's often 2-3 of us for many hours, the FC is usually 0 well before we even get out!

Yes, test more often, especially after use. You don't want it to let it drop to zero if possible. After a use is especially critical to test and adjust FC, as it takes days sometimes to burn off the waste from a long soak.

You can turn the heat down but don't turn the filter off.

That said, I leave my tub at temp year round, as I want it ready to use whenever I want, and I don't want to wait hours for it to heat up.

Dichlor is generally powder. It adds chlorine and CYA, and is acidic. You don't need it if you have straight CYA, as you do. Just use that as needed to maintain CYA as needed.

Okay, what temps do you leave yours at when not in use? You have a filter that will turn on and off in a cycle? I have yet to see this one ever turn off, maybe because I havent let it sit long enough.

Good to know about the powder, using straight CYA and supplementing with CL will be what I'll do. CL is holding beyond steady now so going to check it again tomorrow.

When you say you bring it up to SLAM before you use it, do you test before you get in or just add CL? When you get out do you assume it's down to zero and add CL again based on a 0-slam calculation or do you break out the test kit again at the end of the night and do a test before packing up for the evening?
 

jseyfert3

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Also for a general update, I am going to stop with the CL for now. The reading is currently way overboard, 20 drops in and it still didnt turn from red to clear so going to let that fade. Also because of the ultra high FC I can't get a CH reading, so I will try that once things calm down as well. I think anything in there right now should be dead, I may have gone overboard with the SLAM.
Yeah you always want to make sure things are well mixed and you add the appropriate amount. You don't want to overshoot SLAM levels by a drastic amount. Are you using a 10 mL sample for the FC test? If so SLAM for a CYA of 30 is still 12 and you hadn't gotten to 12 yet, but if still bright red after 20 drops on a 10 mL sample then yeah you're way over that.

I didn't think the CH test was sensitive to FC. Is that just not working right now?

Picked up a 50lb bag of calcium hardener so I am ready to go once my numbers start dropping.
Do you have a lot of CH in your tap water? Actually do you know your tap water TA and CH? It seems unlikely you will need to add CH, for an inflatable tub (actually most standalone tubs) CH is only really needed to prevent foaming.

Going to get one of those at Tractor Supply. They were supposed to have some in stock but didn't so they are going to get me one. Would rather go there than Amazon if I can. I got the 32 oz one which has single oz markers for now which will work.
Yeah I got the 8 oz one cause it had the biggest spacing for measuring out small amounts of chlorine and acid. Actually I have two, one for chlorine, one for acid. And for my pool I have a pair of 64 oz ones for adding chlorine and acid.

Okay, what temps do you leave yours at when not in use? You have a filter that will turn on and off in a cycle? I have yet to see this one ever turn off, maybe because I havent let it sit long enough.
As I mentioned I don't turn mine down. We have a 240 volt, well insulated spa, so turning it down does not have as much savings as it would on an inflatable spa (though an inflatable spa takes forever to heat up!). I'd rather pay a little more and have it ready to use anytime. I think I'll use it tonight. Drink a beer as the snow falls around us.
full


My prior Intex inflatable spa never shut off, but the pump is only 50 W so negligible power usage. I'm assuming your inflatable is similar, and is designed to filter 24/7. The pump in my Intex was weak and slow, which is why it runs all the time.

On my pictured above spa, yes, it does set filter cycles like twice a day for 15 minutes or so, but during a filter cycle there are two 3 HP pumps running on high that move the water really quickly. In between filter cycles it kicks on a single pump on low every 15 minutes for a couple minutes to check temp, and if it needs heat it keeps the pump on low while the heater runs.

When you say you bring it up to SLAM before you use it, do you test before you get in or just add CL? When you get out do you assume it's down to zero and add CL again based on a 0-slam calculation or do you break out the test kit again at the end of the night and do a test before packing up for the evening?
I test the FC, then use PoolMath to calculate the amount of bleach to add to bring it to SLAM, add the bleach spread out a bit in the water and mix. On Intex spa I would use the bubbles for 30 seconds or so to mix it in. On my current spa I run both pumps on high for a minute or so. I do not re-measure after adding bleach before getting in. It wouldn't hurt to do that once or twice, I've done that in the past and PoolMath and my measuring has always been spot on. But sometimes spa manuals don't report the correct water volume, or you may have accidentally typed a chlorine % wrong, so knowing you have everything set up in PoolMath correctly is a good thing.
 
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Skenn81

Well-known member
Apr 23, 2018
218
Florida
I didn't think the CH test was sensitive to FC. Is that just not working right now?

I found a couple of threads on here speaking of the issue, when your chlorine is through the roof you need to do the test differently. Example: CH test never turned blue... went from purple to clear, then yellow

My prior Intex inflatable spa never shut off, but the pump is only 50 W so negligible power usage. I'm assuming your inflatable is similar, and is designed to filter 24/7. The pump in my Intex was weak and slow, which is why it runs all the time.

Looking at the manual now, the heater power is listed at 1,300 watts. Nothing listed for the pump. Model is SSP-10-1. So when you had the Intex you really just let it run non stop? What temp did you leave it at when it wasnt in use? 2 degrees an hour means we need to plan quite ahead of time to get it up to 104 if its below that.

As for calcium hardness of the tap water, not sure actually. I do know we all have down here what is considered hard water. Gets people all itchy at times and makes it so you need to clean the shower doors often. Never tested it straight out of the tap.
 

jseyfert3

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Looking at the manual now, the heater power is listed at 1,300 watts. Nothing listed for the pump. Model is SSP-10-1. So when you had the Intex you really just let it run non stop? What temp did you leave it at when it wasnt in use? 2 degrees an hour means we need to plan quite ahead of time to get it up to 104 if its below that.
I think I measured my pump power draw using my Kill-A-Watt. And yes, if the tub was filled I left it on and filtering 24/7. Like my current hot tub, I left it at temp, unless I was on vacation or otherwise gone for a while, because at 2 degrees per hour it takes forever to reheat.

As for calcium hardness of the tap water, not sure actually. I do know we all have down here what is considered hard water. Gets people all itchy at times and makes it so you need to clean the shower doors often. Never tested it straight out of the tap.
It's usually a good idea to test your tap water for TA and CH. Lets you know what you're dealing with. For example if you know your tap water has a TA of 150, and like most hot tubs you've worked the TA down to ~50, you'll know that when you top off the hot tub you'll expect the TA to rise some.

Also if you just filled the tub it's going to match that of your tap, so you could test your tap for CH now rather than wait for the FC to drop.
 
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