To ozone or not to ozone? Is that the question?

[linksteve]

First... God bless you guys.  What a wealth of info you all provide tub neophytes like me.  Thank you
Second... If the answer to my questions below are well described in another thread, please say so, and if possible direct me to the thread.

Here goes.

I live in So. Maine.  Just bought a little house.  Building a deck.  And...I just purchased a mint 2008 Sundance Chelsee. Built a level stone pad. Moved it into place, fired it up.  Amazing!  Then chemistry started to happen.  The stock ozonator is shot, so I disconnected it and plugged the single line (FYI that seemed strange). A local company guided me to add the metal removal liquid, bring PH up and then add 3-4 tablespoons of chlorine. Everything was good.  The next day the water was clear.  I was psyched.  My aching back was never so happy.  After a couple days I added 2 more tablespoons chlorine.  Everything was dandy.

Then this morning...super cloudy water.  Tested water. No chlorine.  Added 2 tablespoons. Waited 3 hours and added 8 tablespoons Renew. Now waiting.  For how long...is anyone's guess.

My questions are:

If two of us use tub 2-3 times per day for a total 45 minutes...how often, when and how much chlorine should I add? leave jets on or off? cover open or closed?

I'm thinking a new CD ozonator would be a good idea.  If you agree...what kind?

Thank you in advance

Link in Maine

 

[chem_geek]

An ozonator works better either in situations with high bather load such as using the spa every day or when you use bromine instead of chlorine.  It doesn't work so well if you don't use the spa frequently and are using chlorine.  The reason is that ozone depletes chlorine -- they react with each other.  So it's much harder to maintain a residual of chlorine in the spa when it has an ozonator.  If you soak every day, you can add chlorine every day after your soak and do fine.  In that situation, the ozone reduces chlorine demand because ozone can oxidize some of the bather waste.

As a very rough rule-of-thumb that is very dependent on the strength and runtime of the ozonator, an ozonator roughly cuts in half the chlorine demand from oxidizing bather waste but roughly doubles (or more) the chlorine demand in between soaks (say, starting 24-hours after a soak).

As for how much chlorine needs to be added, the rough rule-of-thumb for soaking in a hot (104ºF) spa is that every person-hour takes 3-1/2 teaspoons of Dichlor or 3-1/2 fluid ounces of 8.25% bleach or 7 teaspoons of non-chlorine shock (MPS) to oxidize the bather waste.  This assumes no ozonator.  With an ozonator, the amounts needed are roughly half (though depends on ozonator strength and on-time).

Your bather load is high using the tub with 2 people for 45 minutes.  Spreading it out vs. all at one time doesn't make a huge difference unless you get sweaty/dirty in between and don't rinse off before getting in each time.  2*(45/60) = 1.5 person-hours so that would take 5-1/4 teaspoons of Dichlor (1-3/4 tablespoons) for the day.  It sounds like you've been adding less than this since you mentioned adding 2 tablespoons but then letting it go for a couple of days.  If you soak every day you need to add nearly 2 tablespoons every day.  The real rule is to add whatever it takes such that you have a small residual (say 1-2 ppm FC) of chlorine for the start of your next soak.

Note however, that using Dichlor-only will build up the Cyanuric Acid (CYA) level so your water will get dull/cloudy sooner since the higher CYA level makes the chlorine less effective so won't be able to oxidize bather waste fast enough.  An ozonator will help in your situation, but you could also use the Dichlor-then-bleach method to prevent the CYA buildup.  That requires some special care, however, to prevent the pH from rising -- specifically it requires lowering the Total Alkalinity (TA) to around 50 ppm, targeting 7.8 as pH, and using 50 ppm Borates (most easily added from boric acid) for additional pH buffering.

Others can recommend specific CD ozonators for you.

 

[linksteve]

Thanks chem geek.  That lesson is extremely helpful.  As you suggested...I have been adding 2 tablespoons chlorine daily.  Usually in the evening after our final soak. I run jets with cover off for 20-30 minutes...then close it up for the night.  In the morning its clear and inviting. 

Can you explain the need for "shock"...and how/when to execute it? I read threads about chloride, free chlorine, etc. and get a little nervous that just adding chlorine will eventually backfire.  I inherited some Leisure Time "Renew".  Is this the MPS shock product you referred to?  Is there a need or benefit is adding a "clarifier" or "softener"?  Thanks in advance

 

[chem_geek]

If you consistently maintain a chlorine level in the spa, which generally means dosing appropriately after each soak and dosing in between soaks if you don't soak every day or two, then you should never have to shock your spa.  That's most especially true if using the Dichlor-then-bleach method.  The reason is that you are continually oxidizing bather waste and disinfecting (killing pathogens) by maintaining the chlorine level.  Shocking is a crutch for methods that don't work well by themselves -- including Dichlor-only after the CYA builds up too much because it makes the chlorine so ineffective that it us unable to oxidize bather waste quickly enough unless you raise the FC to higher levels (i.e. shocking).  Note that it sounds like you are only using Dichlor in which case you'll need to change the water about twice as often compared to Dichlor-then-bleach.

 

[linksteve]

I have seen dichlor bleach mentioned in various posts. Until I add an ozonator should this be my protocol?  If so, what would that look like?  If I continue with dichlor only with the use pattern described above, and my water remains clear, is anything else needed? Will a scented salt screw things up?  How frequent would water changes be needed?  How do you know?  Many thanks in advance for your ongoing guidance.

 

[chem_geek]

You can certainly use the Dichlor-then-bleach method before getting your ozonator.  The scented salt should not affect it.

Since it takes some effort for the transition, usually done at the start of a water change, I'd say it only makes sense to switch if you are a ways away from your next water change.  If you are, then you just start using unscented regular (concentrated) bleach, NOT splash-less or "outdoor".  Clorox concentrated 8.25% bleach is an option but there are less expensive equivalents that are the same such as Great Value bleach from Walmart.

Because Dichlor is net acidic and bleach is not, you need to have a lower Total Alkalinity (TA) of around 50 ppm when using bleach and should add 50 ppm Borates to the water for additional pH buffering.  You can add the borates by using boric acid you can get at Duda Diesel or The Chemistry Store.  If you haven't been adding any baking soda (Alkalinity Up) or pH Up products to your spa when using Dichlor, it's possible your TA is lower now.

Before anything else, however, you should get yourself a proper test kit if you don't have one already.  The Taylor K-2006 is the best to get and you can get it at a reasonable price at TFTestkits.net.  Also, before your next water change, get some Ahh-Some since you'll want to get a clean start using this product just before you change you water since it removes greases, oils, and biofilm from piping and other areas where there may not be constant circulation (such as spa jets, especially if not regularly used).

As for water changes, for Dichlor-only the "standard" Water Replacement Interval (WRI) (that I've adjusted to use person-hour input) gives a decent approximation IF your spa is hot (104ºF):

WRI = (1/9) x (Spa Size in Gallons) / (# of person-hours per day)

so in your case this would be (1/9) x (365) / (2*(45/60)) = 27 days

I got your spa water volume from this manual that said the Chelsee was 365 gallons.  With the Dichlor-then-bleach method, you should be able to go at least double the time between water changes so instead of 1 month that would be 2 months.  With an ozonator, that should help as well though it's less clear by how much -- maybe if you are lucky it will let you double the time again to 4 months, but you'll see how it goes (I'm guessing it won't help quite that much -- maybe to 3 months).

 

[linksteve]

Thanks chem geek!  Every 27 days. Whoa. Are there identifiable variables that a water change is needed? Odor, cloudy, FC unresponsive to dosing, etc? Thanks

 

[Levelheadsteve]

My manual says specifically to not use liquid bleach. Is it really a problem to add a little liquid bleach to a standard fiberglass tub?

 

[Tman122]

Thanks chem geek!  Every 27 days. Whoa. Are there identifiable variables that a water change is needed? Odor, cloudy, FC unresponsive to dosing, etc? Thanks

Your water is slower when it needs to be changed. Bubbles move slower in the water and it becomes cloudier quicker and stays longer when you run the jets.

 

[chem_geek]

My manual says specifically to not use liquid bleach. Is it really a problem to add a little liquid bleach to a standard fiberglass tub?

Some spa manufacturers say that because 1) if you used only bleach with no CYA then the active chlorine level would be too high and 2) using bleach which itself is close to pH neutral after accounting for chlorine usage/consumption nevertheless has pH rise from carbon dioxide outgassing so requires special handling to avoid that since higher pH can result in calcium carbonate scale.

If you use bleach you should have CYA in the water first which you can either do via adding pure CYA (that dissolves slowly) or more conveniently start out using Dichlor until you've cumulatively added 33-44 ppm FC which results in 30-40 ppm CYA.  After that you use bleach except once a month you use Dichlor for a day.  When you switch to using bleach, you want the TA to be much lower at around 50 ppm and you need to have additional pH buffering by using 50 ppm Borates most easily added from boric acid.

 

[chem_geek]

Thanks chem geek!  Every 27 days. Whoa. Are there identifiable variables that a water change is needed? Odor, cloudy, FC unresponsive to dosing, etc? Thanks

In addition to what Tman122 wrote, the water will be a little dull but you'll probably not notice that until you do the water change when you'll say "gee, that's noticeably clearer".

Your case is unusual because you are using the spa a lot more than most people.  It's the buildup of CYA from the Dichlor that is the problem as it makes the chlorine less effective (lowers the active chlorine level) so oxidizes your bather waste more slowly.

 

[Levelheadsteve]

Thank you for the information chem geek.

 

[HomePC]

My ozonator went out about 9 months ago. I just capped the feed line to the tee and pulled the ozonator out. Haven't replaced it yet and I haven't noticed any difference. My tub gets light use. Maybe 2-3 times a week. I add a cup of bleach about every month along with stain/scale remover and bromide tablets.