Where has my chlorine gone??

[iceno9]

Ok...so the first time i have filled my hot tub and tested the water with some new test strips ( ones i got with my second hand tub are several years out of date!).
We have soft water, total hardness is low as is the PH, and of course no chlorine.

Anyway - added TA up = Total Alkalinity now fine.
Added PH up = PH is just about ok, maybe needs a little more
Added chlorine (couple of teaspoons as tub holds about 1300 liters) - chlorine registers, and can smell it.

Anyway - used the tub a good few times and everytime i check the water, there is very very little free chlorine and no total chlorine. So i have been adding more and more, well over the recommended amount as it just registers very low all the time?!?

I'm confused - why is the chlorine level not going up?

Secondly, water is a little cloudy (i.e. not crystal clear) but doesnt smell. Is this normal or is it a case of using some clarifier?

[chem geek]

Based on your earlier post,

So i have got my second hand tub and have nearly finished wiring it all up.

The tub may have been emptied but the lines not fully blown out so there may be bacterial biofilms there.  Also, being a used tub who knows how well it was maintained.  Even for new tubs, there are greases and sometimes biofilms present from the leftover water in the lines.  So it is a good idea when you get a tub that is new to you to do a decontamination of it.  To remove biofilms and greases, use Ahh-Some®.  Obviously this requires dumping the water after that is used.

If you don't want to do this, you can try superchlorinating but that may not be sufficient.  Also, what is the "recommended amount" of chlorine you are using.  You may just have higher bather load and are not using sufficient amounts of chlorine.  1300 liters is 343 gallons so this is roughly 350 gallons.  2 teaspoons of chlorine is only enough to handle around 30 minutes of one person soaking, assuming you have no ozonator.  Did you soak for longer than 30 minutes or have more than one person soaking?  With no ozonator (do you have an ozonator?) every person-hour of soaking in a hot (104ºF) spa needs roughly 3-1/2 teaspoons of Dichlor or 3-1/2 fluid ounces of 8.25% bleach or 7 teaspoons of non-chlorine shock (43% MPS) to handle the bather waste.

[Vinny]

Besides what chem geek said you mentioned something that can't be happening unless the test strips are bad ... And I'll add that using Ahh-some really cleaned out my lines. I used it 3 times back to back, cleaned the mess it left every time and I still got a mess the next time I used it. I'm convinced it was doing it's job!

If you have some free chlorine you have to have total chlorine -> Total Chlorine = Free chlorine + combined chlorine

[hottubdan]

Most simple answer is chlorine is always gone after a day or so.

[chem geek]

If you don't have an ozonator, then 24-hour chlorine loss in a hot tub is usually 25% or less (but not usually less than 15%).  With an ozonator, the loss is often 50% and can be more.  Ozone consumes chlorine when there is no bather load.

[rin-spa-aic]

Assuming your tub is clean...

Add some borates + muriatic acid.


It worked to stabilize my chlorine levels and reduce the dissipation rate.

[iceno9]

Sorry for the late response.....

Yes the tub has an ozonator, however i suspect it is usless and has never been changed. I asked the former owner and he had no clue as he just said he had it serviced regularly (which i also dont fully believe and there is no paperwork trail).
So i will be looking to replace the ozonator shortly.

Reading the responses leads me to another question.....When to add the chlorine? Before bathing or after?
At the moment i add after on the basis to sanitize after use....but i can see the logic in adding it 10 minutes before bathing?

Also - when to use test strips? If i am testing say after 24 hours of adding the chlorine, then naturally it sounds like it will have gone down somewhat!?

I will look into adding borates and muriatic acid.....

Thanks
Matt

[Vinny]

As far as the ozonator, I haven't used mine in years and I didn't see a difference - you need to take care of the water properly anyway.

When to add chlorine is dependant on how well you take care of the water and how many people are using the tub. If you are diligent in adding chlorine regularly then you can soak before adding chlorine. If you waited days then add some chlorine before going in. If you are having a party then I would add before, during and after with probably a shock dose after to super chlorinate the tub.

My rule of thumb is depending on how many people are using the tub that dictates how much chlorine I put in. So when its just me I put in 3 ppm, when its 2 people I put in 4 1/2 ppm and if its 3 or more ( nor a party) I put in 6 ppm. This is when I use dichlor, if I use bleach I tend to over chlorinate and then leave the cover off longer - usually a 20 minute jet cycle. Nothing wrong with adding more chlorine to kill whatever.

[chem geek]

For 50 ppm Borates, get boric acid from DudaDiesel, The Chemistry Store, AAA Chemical (shipping costs vary depending on where you live).