Pushing the limits of Hot Tub Serum

In the foundational materials on this site (see the Hot Tub  home page) I highlighted that biofilms can survive chlorine concentrations of 1-3ppm — levels that some authorities still promote for regular use.  In addition to ahh-some as a purge product, Hot Tub Serum (or “Serum Total Maintenance”) gives us another tool in our toolbox to combat the problem of biofilms and “bad guys” in general.   Here are the major points of interest that I have established to my own satisfaction via experimentation:

1. The useful drain interval of hot tubs sanitized with “dichlor” (granular Chlorine for Hot tubs)  is limited by the rising accumulation of Cyanuric acid (CYA) which renders Chlorine increasingly impotent as the sanitizer is added on a regular basis.  I’ve been able to confirm that “Hot Tub Serum” is immune to this problem, and continues to attack bad guys no matter what levels of Chlorine and CYA are present.
2. Without automatic sanitizer dosing (a floater, for example) it is not a trivial matter to keep Chlorine levels from dropping into the 1-3ppm region or below, where research has shown biofilms can survive and even grow.   In my experience, Hot Tub Serum is a profoundly effective solution to this problem(when used as directed), as it continues to attack bacteria that would normally survive under these conditions.  It turned out this was just too easy to prove — I let my Spa go to zero chlorine on a number of occasions and each time Hot Tub Serum not only kept my water clear for DAYS (with no chlorine), it also attacked the bad guys and left the evidence thereof on my vessel walls!
3. Hot Tub Serum acts as a sanitizer supplement, working alongside chlorine and even absorbing some small portion of the bather load.  This produces an astonishing “no bather load” sanitizer decay performance, shown in the graph below.  To produce the data represented by the graph,  I let my spa go un-used for a couple of days (to insure there was no bather load), and then dosed to about 5ppm Bromine. I then left the spa, covered and unused, and measured bromine levels over time (the X-axis in the graph is in hours, and extends beyond 6 days).   The upper (dark) line represents the sanitizer decay rate with Hot Tub Serum in the water. The lower two lines represents the decay rate without Hot Tub Serum in the water.
4. Hot Tub Serum is NOT a disinfectant or sanitizer in its own right — and neither is it an oxidizer but it DOES work synergistically with your existing sanitizer program.  For me, this means using Serum along with chlorine or bromine (whatever suits me at the time.  I use both).  The manufacturer has stated that Serum works by breaking down bacterial cell walls, producing a residual  by-product that ends up in your filter.   In poorly maintained spas using Serum Total Maintenance for the first time, the result can be a rather dramatic accumulation of material on the vessel walls or inside the filter compartment.   This tells me that there is likely a coagulant of some sort in this formula.

Pushing the SERUM limits

Now for the fun part.   My next objective was to find out just how long my water would survive with only HOT TUB SERUM present in the water — and no Sanitizer.   I would not be testing the sanitizer decay rate I would simply measure the amount of time it takes for the water to go bad, with zero sanitizer present.   Mindful of the manufacturer’s claims and the label directions (I was about to go well beyond the intended use, with water un-protected by a known sanitizer), I wasn’t sure what to expect but there was only one way to find out:  I used the spa as I normally would, just to introduce a bather load,  but I did not add any sanitizer after getting out.    I left the spa unused, as an experiment to see what happened.   Here’s what happened:

1.  After two days my water was still clear and my sanitizer  level had only dropped from 5ppm to 1.2ppm — that’s a little steeper of a sanitizer decay rate than a normal “no bather load” would produce, but I had to remember that I had just introduced a deliberate bather load to start this experiment — so this decay rate was expected.

2. Over the next day my sanitizer finally reached zero and I “started the clock” — observing  the condition of my water over time.  What I discovered was astonishing:   After 12 hours of no sanitizer, my water was still crystal clear.   After 24 hours — crystal clear.   36-hours — crystal clear.  48 hours  — still crystal clear!  Finally, at 50 hours I went to bed.    Sometime during the night, between 50 and 58 hours without any sanitizer, my water turned bad with the characteristic cloudiness of un-sanitized water.

3.  If that wasn’t fun enough I decided to go one step further:  Having finally obtained bad/cloudy water, I now had the opportunity to see what Serum could do to help the recovery process, all by itself.   I dosed my spa with approximately twice the manufacturer’s recommended weekly amount but added no sanitizer or shock treatment.   Within one hour I started seeing small accumulations of material on my vessel walls and in my filter compartment — as shown in the photo below.  I decided to wipe up this residue with a micro-fiber cloth (essentially supplementing my filters).  I also ran the jets for a few minutes to aid this process.

Here is my filter compartment after adding Hot Tub Serum to known-bad water:  Notice that it produced a “mini purge” by depositing material on the vessel walls.  Using Hot Tub Serum in this manner is WAY outside of the manufacturer’s intentions, but it allowed me to see what it was capable of doing    At the 24-hour mark, I observed a striking improvement in my water — still with NO SANITIZER!  The photo below shows the Before (right side, bad water after 50-58 hours) and the After (left side, 24 hours after dosing with  Hot Tub Serum).

-doug