If you have read the Hot
Tub Chemistry Fundamentals page, you already know a covered
hot tub is more like a sealed tank of water than an open swimming
pool so it does not need a 'daily dose' of chemistry.
You should also be aware most of the instructions
you'll find on hot tub water chemistry are borrowed from the swimming
pool industry and simply don't work in a portable hot tub. That's
why you can follow these instructions to the letter and still get
Plastic vs. Plaster
A fundamental difference between your hot tub and
a swimming pool is construction. A swimming pool is usually made
of concrete and plaster and both these materials are very porous
and very reactive to water chemstry. That means the pool surface
is actually part of the ongoing chemical reaction.
In fact, water chemistry in a brand new pool must
be adjusted to accomodate the changing environment as the concrete
completely hardens over the course of several months..
If the water in a swimming pool is to acidic, it will
slowly dissolve the plaster finish and even start eating into the
concrete structure. If the water is too alkaline, it will leave
crusty scale deposits that must be acid washed and sometimes sand
blasted to remove.
Managing paramaters such as pH, Alkalinity and Hardness
is critical to prevent long-term damage to the surface and structure
of a swimming pool.
Draining a swimming pool to refinish the surface
can cost thousands of dollars.
Your hot tub is made almost entirely of inert plastic.
The only metal component in contact with the water is a heater designed
specifically for the harsh environment of hot tub chemistry.
This means your hot tub is not easily damaged by imbalances
that would otherwise destroy the surface of a swimming pool.
You are much more likely
to damage a portable hot tub by overdosing sanitizer
than by neglecting water balance such as ph, Alkalinity or Hardness.
Hot vs. Cold
If you have ever had food poisoning, you probably
know bacteria can thrive in food if you don't store it properly.
Bacteria reproduces prolificly between 40°F and 140°F.
Outdoor pools in San Diego rarely get above 80°F
even when heated. The cooler water in a swimming pool helps to inhibit
Most portable hot tubs are kept at 100°F or higher
which is smack in the middle of the 'Danger Zone' and a sweet spot
for bacterial reproduction.
The higher temperature in a hot tub also means more
perspiration and body oil and the jets scrub off more dead skin
and loose hair.
This organic waste can become a never ending food
source for bacteria and everything on this buffet line is maintained
at the same temperature as a person with a fever.
All this means a hot tub can go from a sanitary soak
to an itchy rash a lot faster than a swimming pool so the primary
purpose of hot tub chemistry is always sanitation first and foremost.
Hot water promotes bacterial
Check sanitizer level before every soak.
Gallon vs. Gallon
Size, or more accurately volume, absolutely
matters when it comes to hot tub chemistry. A typical residential
swimming pool holds around 15,000 gallons of water. A typical portable
hot tub only holds around 400 gallons of water.
All the extra water in a swimming pool can absorb
and dilute a lot more chemistry and contamination. This means a
pool is much more tolerant of chemical overdose and has a bigger
chemical reserve that prevents dramatic changes in water quality.
Easier to Overdose
If you need to increase Chlorine in a swimming pool by 3.0 ppm you
mght have to add 10 Ounces of Sodium Dichlor.
To achieve the same 3.0 parts-per-million in a hot tub, you only
need to add 0.3 Ounces. This is why it's so easy to overdose a hot
Less Chlorine Reserve
When the swimming pool above becomes contaminated, there
are 10 Ounces of Chlorine in the water available to clean it up.
When the hot tub becomes contaminated there is only
0.3 Ounces of Chlorine available. With less of a reserve, the Chlorine
in a hot tub can disappear a lot faster than in a swimming pool.
Higher Bather Load
The smaller volume of water also means the bather load is more concentrated.
Two people sitting in a 400 gallon hot tub are the same bather load
as 75 people in a typical swimming pool.
The smaller volume of water
in a portable hot tub makes it easier to overdose and harder to
keep sanitary at the same time.