Chlorine management

[Sea Bean]

Hi,

We have a J-365, I think it's about 400 gallons, 2 people use it every other day, sometimes every day, at night (no sunlight hits the water so far except when testing/treating).  We toss in a large capful of "Renew" after each use.  I test & treat the water every few days.  Alkalinity & pH seem to hover in the right range.  Chlorine won't stay up and calcium stays consistently low.   

I toss in chlorine w/ the lid half open, let it simmer w/ jets on for about 20 minutes, then close it.  Dealer said this will preserve life of cover, let's the chlorine off-gas.   

I can get the chlorine up to the right level for a test 20 minutes after applying, but the next time I check...a few hours, the next day, doesn't matter...it's at zero.  I think I'd have to put in a ridiculous amount of chlorine to get it to stay at "5" at all times.  My question is...are you supposed to keep the chlorine at 5 at all times?  Or just apply it, kill the stuff, then a day or two later, apply it again, just to knock the bad stuff down often.

Your thoughts? 

[chem geek]

Are you talking about Leisure Time Renew?  If so, that is non-chlorine shock (MPS), not chlorine (Dichlor).

As for how much you need to dose, it depends on whether or not you have an ozonator.  Without an ozonator, then every person-hour of soaking in a hot (104ºF) spa requires around 3-1/2 teaspoons of Dichlor, 5 fluid ounces of 6% bleach or 7 teaspoons of non-chlorine shock (43%).  Leisure Time Renew is only 32.18% so would be 9.4 teaspoons per person-hour.

Does your spa have an ozonator?  How long do the two people soak?  You may not be adding enough, but you shouldn't be using non-chlorine shock (MPS) alone unless you have a Nature2 silver ion system.  You should be using chlorine instead.  If you want the water to last longer between water changes, then the Dichlor-then-bleach method may be for you, but that requires a lower TA closer to 50 ppm and the use of 50 ppm Borates.

[Sea Bean]

We use LT Renew after each use & LT Spa 56 (chlorine) every few days when I test the chemicals.  We don't have an ozonator.  We do have a UV light & a silver thing.  Last night I put in a lot more Renew.  I guess I'll put chlorine in more often as well.  We'll see how that new regimen works. 

Do you need Renew and chlorine if you apply chlorine every time you go in?  What is the Dichlor-then-bleach method? 

Also, I'm hoping the forum weighs in on the whole "keep it at 5" question...

Thanks, appreciate the help!

[chem geek]

You don't need Renew if you use chlorine after every soak.  If you have "a silver thing" that is working to put in silver ions into the spa, then you could use Renew (non-chlorine shock, MPS) after each soak and use chlorine as needed, usually once per week.  This is essentially the Nature2 approach.

Dichlor-then-bleach is where you initially use Dichlor after a fresh drain/refill for about a week to build up the Cyanuric Acid (CYA) level and then you switch to using bleach instead.  About once a month, you use Dichlor for a day.  The other key factors for this approach that are required to have a reasonably stable pH are that you need to lower the Total Alkalinity (TA) significantly to around 50 ppm and you need to add 50 ppm Borates (usually from Boric Acid or Proteam Gentle Spa).

The keeping it at 5 ppm is more for the MPS maintenance.  For chlorine, you can usually start your soak at 1-2 ppm so that you don't smell much during the soak.  You then blast with chlorine after your soak where the FC will go up as much as is needed to oxidize the bather waste.  That is, the amount is proportional to the person-hours of soaking.  You add enough such that you end up with the desired 1-2 ppm FC residual just before your soak the next day, assuming you soak every day.  If you only soak on the weekends, then with chlorine you need to add more during the week since it will not normally last that long.

This post describes how to lower TA via a combination of acid addition and aeration.

As you have seen, regardless of the system that you use, the key is to use ENOUGH oxidizer to handle the bather waste.  Many people use woefully too little because the single dose recommendation from many dealers isn't scaled up to handle higher bather load situations.  It should be an amount per person-hour.  More people needs higher dosing.  Longer soak times needs higher dosing.  An ozonator (which you do not have) complicates things since it handles some of the bather waste, but in between soak it reacts with chlorine increasing daily chlorine demand.  So an ozonator with a chlorine system is usually helpful if one soaks every day or two but is not so good if one only soaks once or twice a week or less.

[Wizard]

Sounds like you may have phosphates in the water. Most water supplies have them and after a few bathing suits go in you will definitely have phosphates.

[TdiDave]

Sounds like you may have phosphates in the water. Most water supplies have them and after a few bathing suits go in you will definitely have phosphates.

How would phosphates increase chlorine usage?

[Wizard]

Phosphates deplete chlorine and bromine quickly. Chlorine usage can be cut by 50% after eliminating phosphates. I use Sea Klear Spa Phosphate remover but there are others that work well also.

[chem geek]

Phosphates do not react with chlorine or bromine at all.  What happens, mostly in pools, is that phosphates are often the limiting nutrient for algae growth so if one doesn't maintain sufficient chlorine levels to kill off the algae faster than it can reproduce, then higher phosphate levels accelerate that growth making it seem like chlorine is consumed by phosphate, but it's really just consumed by algae growth (i.e. oxidizing algae that is growing faster than chlorine can kill it).  This gets worse over time when one is using stabilized chlorine (Trichlor or Dichlor) products because the increasing Cyanuric Acid (CYA) level lowers the active chlorine level so even when you think you have chlorine, it's actually too low.

In spas, it's mostly bacteria growth rather than algae growth, but usually doesn't happen unless the chlorine gets very close to zero.  However, once biofilms form, then it takes much higher chlorine levels to get rid of them.  Prevention is much easier by maintain proper chlorine levels.

So phosphate removers should be seen in the same vein as algaecides.  They aren't necessary if one maintains a proper chlorine level and doesn't let the CYA get too high.  There are over 30,000 members at Trouble Free Pool plus over a quarter of a million peak visitors during May/June that maintain their pools using chlorine alone without the need for phosphate removers, clarifiers, floculants, enzymes, algaecides or other products.

[Sea Bean]

Thanks for the great info.

[Tman122]

We don't have an ozonator.  We do have a UV light & a silver thing. 

A UV light is a type of ozone generator.