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Simple Hot Tub Chemistry Selector


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Simple Hot Tub Chemistry

  1. Hot Tub Chemistry Fundamentals

  2. Why you can't treat a portable hot tub like a Swimming Pool

  3. Total Alkalinity & pH

  4. Sanitize & Oxidize

  5. Step-by-Step Hot Tub Chemistry Checklist with dosage tables

  6. Simple Hot Tub Chemistry Selector

  7. Hot Tub Chemical Damage

Hot Tub Water Conservation


Hot Tub Electrical Safety

Thank you for your patience. This page is open during construction.

You can find the 'wall-of-chemistry' at any hot tub or swimming pool supply store but, here in San Diego, you can also find pool & spa chemicals at any big-box department or hardware store and even some of the bigger grocery stores.

Many pool and spa stores have 'water analysis computers' and self-help versions are starting to pop up on department store shelves. You can bring in a sample of your water, dip a strip and the computer tells you what to buy. You might not trust a pushy sales person selling the latest 'magic potion' for hot tubs but nobody ever argues with the printout from a pushy computer.

Choosing the right sanitizer and knowing how to use it will filter out most of the frustration associated with hot tub chemistry. It also saves buckets of money.

See Hot Tub Refill Cost and you'll never look at the wall-of-chemistry the same way agian. You can drain and refill the average portable hot tub for around $3.00 worth of water. Nothing on the shelf at any store at any price fixes more problems faster, cheaper or more effectively than dumping the whole mess down the drain and starting over.

See Hot Tub Chemistry Fundamentals for some insight into the marketing machine behind this multi-billion dollar industry and simple facts about a lot of stuff you really don't need to buy or pour into your hot tub.


Sanitizer demand is based on bather load


Selecting the best sanitizer option starts with understanding 'sanitizer demand' and bather load. If you have already read the first two sections of Simple Hot Tub Chemistry, you already know bather load is the biggest variable in keeping a hot tub clean and sanitary.

An open, uncovered swimming pool is exposed to sunlight and a daily load of dust, pollen, insects and other debris that creates a predictable sanitizer demand whether or not anyone swims in the water. A 'daily dose' of sanitizer is needed to compensate for this daily contamination.

A portable hot tub is covered most of the time so sanitizer demand is much lower when the tub is not in use. However, as soon as you sit for a nice, hot soak the much smaller volume of water and the higher temperature in a portable hot tub results in a much higher bather load and much higher sanitizer demand than in a swimming pool.

This is why a portable hot tub can go from clean and sanitary to foul and stinky after just one soak.

Even when a hot tub gets 'rancid' it can be fixed by throwing enough sanitizer at it but the smaller volume of a portable hot tub also means it's much easier to overdose which can cause expensive chemical damage.

Choose a sanitizer based on bather load

When you first get a new hot tub, you might sit in it every day which creates very high bather load and higher sanitizer demand.

After the first few weeks, the novelty often wears off and the frequency of hot tub use may go down dramatically. As bather load changes, so does sanitizer demand. If there is no bather load in a covered hot tub there is very little sanitizer demand.

It's important to select a sanitizer system based on anticipated bather load and sanitizer demand.

A system that automatically dispenses sanitizer 24 hours a day is well suited for a busy hot tub with high bather load. However, the same dispenser can cause chemical overdose and chemical damage if sanitizer output is not adjusted during periods of low bather load or nonuse..

A system that requires manual addition of sanitizers is well suited for light, moderate or intermittent bather load and minimizes the risk of chemical overdose. However, since sanitizer must be added manually before each soak, the risk of infection is higher if this step is overlooked.


Hot Tub Sanitizer Selector Table


Bather Load: Tablet systems are useful if your hot tubs has heavy or consistent bather load because the tablet dispenser delivers a 'daily dose' of chemistry. Manual systems are best suited for light to moderate bather load or intermittent use because you must add chemistry before every soak.

Overall Effort: Ease of use is based on factors such as the number of products you must use, the time you spend testing and adjusting and where you can buy compatible products.

Number of products: Minimum number of products you neede to keep the water sanitary.

Risk of chemical damage: Tablet dispensers automatically release chemistry whether or not your hot tub needs it. If you stop using the tub for a period of time but fail to adjust the chemical dispenser, chemical overdose can quickly lead to chemical damage.

Manual systems only add chemistry when the hot tub gets used so the risk of chemical overdose is much lower provided chemical doses are properly measured and applied. However, the risk of infection is higher if sanitizer levels are not checked and adjusted before each use.

Affects on water balance: Some sanitizers and oxidizers raise or lower pH, alkalinity and hardness which means every time you add sanitizer or oxidizer you spend some additional time correcting water balance.

Sanitizer
Bather Load
Overall Effort
Number of Products
Risk of
chemical
damage
Affects on
water balance
Bromine tablets
Heavy or Consistent
5
4
High
Lowers pH
Lowers Alkalinity
Chlorine tablets
Heavy or Consistent
5
3
VERY
High

Lowers pH substantially
Adds stabilizer

Biguanide
(i.e., BaquaSpa®)
Light to Moderate
4
5
Low
Neutral pH
Bromine 2-part
granular
Light to Moderate
3
2
Low to Moderate
Lowers pH
Lowers Alkalinity
Bromine 2-part
liquid
Light to Moderate
3
2
Low to Moderate
Lowers pH
Lowers Alkalinity
Bromine 1-part
granular
Light to Moderate
1
1
Low
Chlorine Dichlor
+ Minerals
Light to Moderate
1
2
Low
Neutral pH
Adds stabilizer
Chlorine Dichlor
Light to Moderate
1
1
Low
Neutral pH
Adds stabilizer
Chlorine Trichlor
granular
Light to Moderate
1
1
VERY
High

Lowers pH substantially
Adds stabilizer

Chlorine liquid
Light to Moderate
1
1
High
Raises pH substantially
Raises TDS
Chlorine Cal Hypo
Light to Moderate
1
1
VERY
High
Raises pH
Raises hardness substantially

 


Bromine Tablets


Bromine tablet systems are commonly included with new hot tubs as part of the complimentary start-up kit. Tablet systems are very well suited to hot tubs with heavy or consistent bather load because the tablet dispenser can be adjusted to deliver a 'daily dose' of chemistry.

Bromine Tablets
Pros
Cons
  • Constant rate of sanitizer is suitable for heavy or regular bather load
  • Less likely to bleach hair or swimwear
  • No chlorine odor or irritation
  • Tolerates high pH better than chlorine
  • More effective sanitizer than chlorine
  • More stable than chlorine at higher water temperatures
  • Does not add stabilizer byproducts
  • Approved by many state health agencies for use in public hot tubs
  • High risk of chemical overdose and chemical damage
  • Less effective oxidizer than chlorine
  • Requires multiple products
    • Sodium bromide salt
    • Bromine tablets
    • Bromine tablet feeder
    • Non-chlorine shock
  • Lowers pH and alkalinity which must be corrected on a regular basis
  • Higher total cost than chlorine

Important: NEVER mix bromine, trichlor or cal hypo tablets in the same dispenser!

Brand Names (sodium bromide): Jack's Magic® The Yellow Stuff®, Leisure Time® Reserve®, Leisure Time® Sodium Bromide®, Natural Chemistry® Spa Bromine Start®, Rendezvous® Enhance®, Sea Klear® Sodium Bromide®, Spa Choice® Bromine Booster®, etc.

Brand Names (bromine tablets): GLB®, Hasa®, HTH®, Leisure Time®, Natural Chemistry®, Omni®, Rendezvous®, Sea Klear®, Spa Choice®, Spa Essentials®, Spa Guard®, etc.

Brand Names (non-chlorine shock): GLB® Oxy-Brite®, Leisure Time® Renew® & Renew Tabs®, Natural Chemistry® Spa Oxidizing Shocik®, Rendezvous® Activate®, SeaKlear® Chlorine-Free Shock Oxidizer®, Spa Choice® Re-Energize®, Spa Guard® Spa Shock®, etc.


Chlorine Tablets


Chlorine tablet systems are not recommended in most portable hot tubs and will void many manufcturer's warranties. Chlorine tablets are typically made from 'Trichlor' a type of chlorine formulated specifically for swimming pools. Trichlor has a very low pH (2.9) which makes the water acidic and a very high concentration of chlorine which often leads to chemical overdose.

 
Chlorine Tablets
Pros
Cons
  • Constant rate of sanitizer is suitable for heavy or regular bather load
  • Highest concentration of chlorine
  • More effective oxidizer than bromine
  • Less expensive than bromine
  • Readily available at swimming pool supply stores, hardware and grocery stores
  • Widely approved by state health agencies for use in public pools and hot tubs
  • Very high risk of chemical overdose and chemical damage
  • More likely to bleach hair and swimwear
  • Prohibited by most portable hot tub manufacturer warranties
  • Germ killing effectiveness is reduced by high pH often found in hot tubs
  • Less stable than bromine at higher water temperatures
  • Potential for chlorine odor and irritation
  • Requires multiple products
    • Chlorine tablets
    • Chlorine tablet feeder
    • Non-chlorine shock
  • Lowers pH and alkalinity substantially which must be corrected on a regular basis
  • Adds stabilizer byproducts that can inhibit germ-killing effectiveness

Important: NEVER mix bromine, trichlor or cal hypo tablets in the same dispenser!

Chlorine tablets are available in 1" and 3" tablets. The smaller 1" tablets can be used in a floating tablet dispenser. The larger 3" tablets should only be used in an in-line dispenser that is part of the plumbing. 3" tablets should never be used in a portable hot tub.

Brand Names: Aqua Chem®, Blue Wave®, Chem Lab®, Clorox®, EZ Clor®, GLB®, HTH®, In The Swim®, Kem-Tek®, Leslies®, Pool Time®, etc.


Biguanide


Biguanide systems are a bromine and chlorine free alternative that uses a synthetic polymer (PHMB) symilar to chlorhexidene an antimicrobial surgical scrub. It does not affect pH and is not blocked by high pH levels like chlorine.

Biguanide
Pros
Cons
  • No chlorine odor or irritation
  • Less likely to bleach hair or swimwear
  • No bromine
  • Tolerates high and low pH
  • Does not change pH
  • More stable/lasts longer than chlorine or bromine
  • Does not add stabilizer products
  • Prohibited by some hot tub warranties
  • Must use proprietary oxidizer
  • Forms insoluluble particles leading to 'bathtub ring', gummy deposits and potential for biofilm
  • Must use proprietary waterline control product to prevent deposits
  • Must use proprietary filter cleaning product to remove deposits.
  • Use of conventional filter cleaners can permanently damage filters. Cleaning filters with detergents that contain phosphates can block sanitizer.
  • Not compatible with commonly available hot tub products such as sanitizers, oxidizers, clarifiers, etc
  • Must drain/flush/purge all plumbing lines to remove all traces of chemistry before converting to biguanide or converting back to chlorine or bromine
  • Contains hydrogen peroxide which cannot be dumped to a storm drain within city of San Diego
  • More expensive than chlorine or bromine
  • Limited availability (not commonly sold by big-box retailers and not stocked by many swimming pool or hot tub supply retailers)
  • Limited approval by state health agencies for use in public pools and hot tubs

Brand Names: Aqua Finess®, BaquaSpa®, Leisure Time Free®, etc.


Bromine (granular and liquid)


2-Part Bromine systems consist of a sodium bromide salt and a separate oxidizer that must be added to the water manually on a regular basis. Some brands use granular bromide salts while others use liquid.

Manual systems are very well suited for light to moderate bather load or intermittent use because sanitizer will likely have to be added before every soak. Assuming chemical doses are properly measured and applied, manual systems have a much lower risk of chemical overdose and chemical damage because chemistry is only added when the tub actually gets used.

2-Part Bromine
Pros
Cons
  • Less likely to bleach hair or swimwear
  • No chlorine odor or irritation
  • Tolerates high pH better than chlorine
  • More effective sanitizer than chlorine
  • More stable than chlorine at higher water temperatures
  • Does not add stabilizer byproducts
  • Approved by many state health agencies for use in public hot tubs
  • Manual dosing may not be suitable for heavily used hot tubs
  • Less effective oxidizer than chlorine
  • Requires multiple products
    • Sodium bromide salt
    • Non-chlorine shock
  • Lowers pH and alkalinity which must be corrected on a regular basis
  • Higher total cost than chlorine

Brand Names (sodium bromide): Jack's Magic® The Yellow Stuff®, Leisure Time® Reserve®, Leisure Time® Sodium Bromide, Natural Chemistry® Spa Bromine Start®, Rendezvous® Enhance®, Sea Klear® Sodium Bromide®, Spa Choice® Bromine Booster®, etc.

Brand Names (non-chlorine shock): GLB® Oxy-Brite®, Leisure Time® Renew® & Renew Tabs®, Natural Chemistry® Spa Oxidizing Shocik®, Rendezvous® Activate®, SeaKlear® Chlorine-Free Shock Oxidizer®, Spa Choice® Re-Energize®, Spa Guard® Spa Shock®, etc.

1-Part Bromine

2-Part Bromine
Pros
Cons
  • Single product - Does not require separate oxidizer
  • Less likely to bleach hair or swimwear
  • No chlorine odor or irritation
  • Tolerates high pH better than chlorine
  • More effective sanitizer than chlorine
  • More stable than chlorine at higher water temperatures
  • Does not add stabilizer byproducts
  • Approved by many state health agencies for use in public hot tubs
  • Manual dosing may not be suitable for heavily used hot tubs
  • Less effective oxidizer than chlorine
  • Lowers pH and alkalinity which must be corrected on a regular basis
  • Higher total cost than chlorine

Brand Names: Spa Essentials® Brominating Concentrate®, Natural Chemistry® One Step Brominating Concentrate®, Leisure Time® Brominating Granules®, Spa Guard® Brominating Concentrate®, Spa Time® Brominating Granules®, etc.


Chlorine (granular and liquid)


Chlorine (Dichlor)

Title
Pros
Cons
   

 

Chlorine (Dichlor + Silver)

Title
Pros
Cons
   

 

Chlorine ('Trichlor' granular)

Granular Trichlor is not recommended in most portable hot tubs and will void many manufcturer's warranties. Trichlor has a very low pH (2.9) which makes the water acidic and a very high concentration of chlorine which makes it very easy to accidentally overdose the small volume of water in a portable hot tub.

Pros
Cons
  • Highest concentration of chlorine
  • Single product - Does not require a separate oxidizer
  • More effective oxidizer than bromine
  • Less expensive than bromine
  • Readily available at swimming pool supply stores and some big-box stores
  • Widely approved by state health agencies for use in public pools and hot tubs
  • Manual dosing may not be suitable for heavily used hot tubs
  • Very high risk of chemical overdose and chemical damage
  • More likely to bleach hair and swimwear
  • Prohibited by most portable hot tub manufacturer warranties
  • Germ killing effectiveness is reduced by high pH often found in hot tubs
  • Less stable than bromine at higher water temperatures
  • Potential for chlorine odor and irritation
  • Lowers pH and alkalinity substantially which must be corrected on a regular basis
  • Adds stabilizer byproducts that can inhibit germ-killing effectiveness

Brand Names: BioGuard® Power Chlor®, Kem Tek® Super Shock®

Chlorine (liquid)

Sodium Hypochlorite is liquid chlorine bleach.

Sodium Hypochlorite
Pros
Cons
  • Single product - Does not require separate oxidizer
  • More effective oxidizer than bromine
  • Least expensive form of chlorine
  • Readily available at multiple retail outlets
  • Widely approved y state health agencies for use in public pools and hot tubs
  • Does not add stabilizer byproducts like Dichlor and Trichlor
  • Manual dosing may not be suitable for heavily used hot tubs
  • Lowest concentration of chlorine
  • Higest concentration of dissolved salts
  • Raises pH and alkalinity substantially which must be corrected on a regular basis
  • Germ killing effectiveness is reduced by high pH often found in hot tubs
  • Potential for chlorine odor and irritation

Brand Names: Aqua Chem®, Chlorox®, HTH®, In The Swim®, Kem-Tek®,

Chlorine (Cal Hypo)

Calcium Hypochlorite is often sold as "shock" or "super-shock" for swimming pools. Cal Hypo is not recommended in portable hot tubs in San Diego because it increases calcium hardness which will cause scaling.

Title
Pros
Cons
  • Single product - Does not require separate oxidizer
  • More effective oxidizer than bromine
  • Less expensive than Dichlor or Trichlor
  • Aavailable at multiple retail outlets
  • Widely approved y state health agencies for use in public pools and hot tubs
  • Does not add stabilizer byproducts like Dichlor and Trichlor
  • Manual dosing may not be suitable for heavily used hot tubs
  • Raises Calcium Hardness substantially - Not suitable for use in hard water - Causes scaling
  • Raises pH and alkalinity which must be corrected on a regular basis
  • Germ killing effectiveness is reduced by high pH often found in hot tubs
  • Potential for chlorine odor and irritation

Brand Names: Blue Wave® Blast Out®, Dry Tec® Granular Shock®, HTH® Super Shock and Swim®, HTH®, Ultra Shock®, In The Swim® Pool Shock®, Robelle® Powdered Shock®, Robelle Ultima TKO Shock®,

IMPORTANT: Calcium hypochlorite is sometimes available in 1" tablets. NEVER mix bromine, trichlor or cal hypo tablets in the same dispenser!

Title
Pros
Cons
   

 


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