Hot Tubs and Spas purging and cleaning

when “Shock level and maintain” doesn’t work

Greetings Hot Tub enthusiasts.  This post addresses a common “rescue prescription” for bad water:  The SLAM, or “Shock Level And Maintain”.  Its basically what the name implies — raising the level of chlorine in your water to a very high level, and then maintaining that level for some period of time.  It’s a procedure to use when you have a problem to solve — so let’s first talk about the problem, and then an alternative solution that is easier on your equipment.

Hot tub owners usually don’t take any action or look for any “rescue prescriptions”  unless there is a visible problem — cloudy water, for example, water that “won’t balance”, or bad odor.  In some cases of preventable neglect, bacterial contamination can cause extreme sickness and even death — even when the water looks good!  Check out the following extraordinary story involving a hot tub display at a local Fair:

Hot tub display likely source of North Carolina outbreak: officials

I should note that in cases of a known outbreak, and especially when the public is involved, a full-on decontamination procedure is required, both by local authorities and good common sense.  Typically, however, most owners of residential hot tubs and spas are not trying to solve a known bacterial outbreak where someone got sick — at least I hope not!  They are trying to solve a water maintenance problem — and the SLAM procedure is often prescribed as the solution.  But why would you SLAM when you don’t need to?

When the only tool in your hand is a hammer, then everything starts to look like a nail

Unfortunately, when the problem in your water is not well understood, the solutions prescribed are either not very effective or take the nuclear approach — the bigger the bomb the more effective they are.  In the case of the “shock level and maintain” — it may work, or it may not, and if it doesn’t work the usual approach is to “shock and maintain” at even higher levels.  Why?  because the real problem wasn’t well understood to begin with.

Enter stage left:  Biofilms

Dealers dismiss the problem, manufacturers ignore it, and well-meaning folks misunderstand them and pretend they don’t exist, but biofilms are a thing, no matter what some store or manufacturer or other spa owner may have told you.   One very interesting “blissfully unaware”  forum post of many years ago even suggested that we should be able to live peacefully along with biofilms in our hot tubs because, after all, rivers and lakes have biofilms on every rock and branch, and we don’t get sick when we swim by! I guess when you have a  few billion gallons of water and your own stabilized eco-system you can say that.  Until then, 100 gallons of 104 degree (F)  water per bather is, well, a petri dish.  We don’t want “healthy water” we want “dead” water!

But I digress.  Elevated levels of chlorine (“SLAM’ing”) can certainly kill unprotected bacteria, but usually just attenuates biofilms.  Why do we use chlorine then?  Because its kill rates are well understood!   Check out this page from the Centers for Disease Control and Prevention (the CDC).  Look closely at the names of the known pathogens and their respective kill rates:

With that, I don’t fault the prescribers of SLAM or even full-on decontamination procedures — if chlorine is the only tool in your toolbox then you use that tool as best you can within its limitations.    Basically, the established state-of-the-art is this:  The nastier the bad guy, the more chlorine exposure you’re supposed to hit it with.   For example, “Crypto” (a particularly nasty bad guy) takes over 240 hours (at 1ppm) to kill! You see, we’ve been conditioned to accept that if a little doesn’t work, then a lot will work better. Bigger bad guys get bigger bombs.

If I have captured your attention by now, please see the foundational materials referenced on the Hot Tub home page of this site — there I present more material on the nature of biofilms and my own journey in solving that problem in my own spa.  Biofilms can cause all sorts of water maintenance issues in a spa but, as I found, SLAM’ing isn’t  necessarily the right solution.

SL without the AM

Reviewing the nature of biofilms (see previous reference), we know that they stick to pipes,  form their own colonies, re-generate very quickly, consume sanitizer,  and can even become chlorine resistant.  In severe cases, biofilms provide safe-harbor protection for known pathogens — including Legionella for example.  The problem here is that chlorine doesn’t soften or break up biofilms or release them from the walls —  it only attenuates them and makes them mad (seriously.  read the foundational materials about biofilms regenerating with vengeance).  SLAM’ing may be well intentioned, and may even work — but the high chlorine levels can also put unnecessary stress on your equipment.

Enter Stage Right:  Carpet Bombers

As of this writing, and to the best of my own understanding, the only way to rid your spa of biofilms is to break them up and release them — then and only then will “sane” levels of chlorine be effective.  I’m going to use a war analogy  here because we are definitely “at war” with biofilms:  Why do they send out the carpet bombers to soften up the battle field before sending in the ground troops?  Because it works.  And when Spa owners soften up the biofilms first,  chlorine can move in for the complete kill.  In short, carpet bombing allows us to “Shock” (SL) without the “Maintain” (AM).

In different post I corrected a water problem with just a single shock treatment (the “Shock Level” without the “Maintain”), because I had the QUAT-based formula of “Hot Tub Serum” already in my water.  You can find that post here:

Pushing the limits of Hot Tub Serum

In that particular experiment my water was restored to 80% clarity with a single application of the Serum, with no chlorine in the water!  I pushed the ‘Serum to its limits with a higher dose than prescribed, but the exercise revealed what the product was capable of.  The remaining 20% of water clarity was restored with a single shock-level dose of chlorine, which did its work in about 8 hours — a task that usually takes 24-72 hours at least in my experience.

More generally, using Hot Tub Serum (Total Maintenance) keeps the biofilms “at bay” if you will –it softens them up so that chlorine can do its job. When used as directed, the Serum will actually do a “mini purge” and place a small release on your vessel walls or in your filter compartment — if there is something to release of course.   The product is even EPA registered to control biofilms when used as a regular maintenance product.    Yes, I am impressed with EPA registration, and I remain surprised that other manufacturers haven’t tried to follow suit, or even fake it.

What do I do for more persistent problems?  I have coached several through the purge process of using Ahh-Some.  I use it on EVERY drain — but I realize some folks are just not there yet, and therefore will have to accept that biofilms tend to build up over time and sometimes require one (or more) rescue purges with Ahh-Some to eradicate them.  Ahh-Some contains a CRAZY strong set of carpet bombers — with nearly 50% “QUAT” concentration, which I assume is either by weight or by volume – I can’t tell.  In any case I have personally  discovered that the contaminants released by Ahh-some consumed 75% of the chlorine in my water in just a few minutes. That’s some serious carpet bombing.

As a post script — I have come to know that the light blue gel that is marketed as “Ahh-Some” is also available in a darker purple color and called Serum “Total Cleanse”.  I suppose this is to position it along with the previous “Serum Total Maintenance” product.  In any case, the blue or the purple gel is all the same, very  high QUAT concentration that delivers some serious carpet bombing.  Clearly, that’s why it works better than the others.


Here’s to “dead” water,



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