Silk Balance and Rapid Chlorine Consumption

[Dr. T.]

Hi Everyone,

I'm the owner of a Caldera Vanto - my first hot tub, and I'm pretty freakin' excited about it, given the cold Michigan winters 

My salesperson gave me a free Silk Balance trial, and I know there are ALOT of opinions about it (and on this board, too).  As of today, the tub has had water in it for only eight days.   The startup chemicals I received were:

Silk Balance, Enhanced Shock (SpaGuard brand, 58.2% sodium di-chloro-s-triazinetrione) and Chlorinating Concentrate (SpaGuard brand, 99% sodium di-chloro-s-triazinetrione dihydrate).  Her startup instructions were (after adjusting alkalinity and pH), shock on day one and dose Silk Balance on day two.  Shock weekly and dose silk balance weekly (though not on the same day).  Maintain about 2 ppm Cl with sanitizer.

Granted we have had high usage (it's NEW), but I can't seem to keep a measurable concentration of Cl in the tub.  Example:  My wife and kids were in the tub yesterday for about 15 minutes, then I got back in for about 15 minutes later that evening.  Once I got out I added two capfuls (1 TBSP) of the sanitizer, and this morning my Cl ppm reads zero.  Today was the first time I measured my "capful" and found it to be only 0.5 TBSP - I thought each was 1 TBSP.  Ultimately, it's my understanding I should probably be adding 2 TBSP after each use (my error), but really?  Zero PPM after adding 1 TBSP the evening before?  Despite this, water quality is great (visually).

My pH is about 7.6, alkalinity is near 100 ppm, and my phosphates are near 500!!  Out of the tap, phosphates are about 100, so I've introduced lots.  This can come from high usage (detergents, etc), but I've also heard that Silk Balance, though the composition is proprietary, is built around a phosphate buffer.

On a different but related note, not sure if I'll stick with Silk Balance after the bottle I was given runs out.  Given that this is my first hot tub, I don't have a comparison of WITHOUT Silk Balance.  Although I'm sure it is reducing the surface tension of the water and helping reduce the buildup of biofilm, I don't feel any silkiness in the water.  Regarding the lower recommended Cl concentration (2 ppm) with Silk Balance version without Silk Balance (3 to 5), I don't see this as being worth the money...

Suggestions and opinions are welcomed!

[chem geek]

1 tablespoon of Dichlor should handle around 50 person-minutes of soaking.  Your wife and kids I'll count as 3 people so between them and you for 15 minutes that is one person-hour of soaking.  So you didn't add enough chlorine to handle the bather load, especially since the capful was only 0.5 tablespoon.  This presumes you don't have an ozonator.

With no ozonator, the needed amount is 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 oxidize bather waste.

Don't worry about the phosphates level.

If you want to have your spa water last longer, then you should consider the Dichlor-then-bleach method because using Dichlor-only builds up Cyanuric Acid (CYA) that lowers chlorine's effectiveness.  By using Dichlor initially to build up the CYA level and then switching over to using bleach, you can go at least twice as long before needing a water change.

Also, even with a new spa there are often greases and sometimes biofilm from factory wet testing so you should get Ahh-Some so at least you can use it just before your next water change.

[Dr. T.]

Thank you for your input.  Can you help me understand how to use the Chlorine Granules and Enhanced Shock?  The salesperson who sold me my spa gave them to me as a "starter kit" and instructed me to use the shock once weekly (dose Silk Balance on the following day) and repeat this weekly.  Use chlorine granules to keep Cl at 2 or 3 ppm.

What I've read so much about on this board and others is that shock should be added after each use...  Can you help clarify?  Well...  actually, my water is quite clear...

[chem geek]

There is no difference between "shock" and simply adding chlorine.  Adding enough chlorinating granules to keep the FC at 2 ppm means having to add a substantial amount added after a soak.  In other words, the instructions to maintain chlorine require significant additions of chlorine after a soak.  Whether you call that "dosing the correct amount to maintain chlorine" or calling it "shocking with chlorine" is irrelevant.

So that begs the question of what you are doing weekly with "shocking" and the answer is that you don't need to do that weekly if you are properly dosing with chlorine after each soak and maintaining a chlorine level.  Technically the "Enhanced Shock" may have both Dichlor (chlorine) and non-chlorine shock in it, but chlorine alone is sufficient to handle bather waste.  What the Enhanced Shock does with its non-chlorine shock is be able to oxidize some of the bather waste which will lessen the rate of buildup of Cyanuric Acid (CYA) that reduces chlorine's effectiveness.

So you could use some of the Enhanced Shock after each soak and forget adding any weekly.  As to whether the Enhanced Shock will actually handle your bather waste well, you'll have to see.  Non-chlorine shock will register as Combined Chlorine (CC) in DPD chlorine test kits unless you get a special interference remover chemical for the kit.

[Dr. T.]

I don't want to sound lazy, but my understanding is that adding an oxidizer (like the enhanced shock, MPS, etc.) requires that you keep your tub running while open for awhile (20 minutes) so the resulting gases can leave.  I do this (currently) once weekly.  But daily?  Especially in the winter (brrr...).

[Sam]

I don't want to sound lazy, but my understanding is that adding an oxidizer (like the enhanced shock, MPS, etc.) requires that you keep your tub running while open for awhile (20 minutes) so the resulting gases can leave.  I do this (currently) once weekly.  But daily?  Especially in the winter (brrr...).

Your jets should be on a timer and shut off themselves.  As to leaving the cover open, a lot of people don't do this.  They just close the cover and go in.  The off-gassing will slowly corrode your cover more than if you left it open, but you may consider the trade off worth it.

[chem geek]

Also, outgassing occurs from all oxidizers when they react with bather waste, but it's chlorine and bromine products that outgas substances that degrade covers faster.  MPS byproducts don't degrade covers as quickly (it's mostly just oxygen as the byproduct).

[Dr. T.]

Hmmm...  So using a daily "enhanced shock" containing Cl and MPS (or whatever the oxidizer in the product is), if added after bathing and cover down, will not increase the rate of f-ing up my cover than simply using dichlor after bathing?  Not implying that you're wrong in any way, but this does seem to go against what most of my internet searching has led me to believe.

[chem geek]

Assuming that  your "enhanced shock" amount you use ends up adding less chlorine than if you were using Dichlor-only, then yes you should have less chlorine and chloramines outgassing so have less damage to the cover.

Nature² with MPS has less cover damage than Dichlor-only (or Dichlor-then-bleach) and that has been stated by several spa professionals who see these different systems.  I don't know what Internet sources you are referring to.  Perhaps you could link to them so we can figure out what they mean.