Affordable Hot Tub Repair

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Hot Tub Chemistry Fundamentals


Hot Tub Repair

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

Filtering Out the Frustration

After many years of talking to hundreds of portable hot tub owners, I've found a few, simple misunderstandings cause almost all of the frustration and nearly all the chemical damage that can happen when hot tub water chemistry goes wrong.

  1. A fresh batch of water is the cheapest, fastest way you can solve complex water problems
  2. Filtration is the first step in fixing any hot tub water quality problem.
  3. Chemical overdose is the leading cause of chemistry problems and expensive chemical damage
  4. "Bather load" determines how much chemistry a portable hot tub needs
  5. You don't need most of the stuff on the shelf even if it came with your new hot tub

$4.00 Buck Chuck Rule:

Even here in San Diego with some of the highest water rates in the country, it still only costs about $4.00 to refill the average portable hot tub.

A fresh batch of water is the least expensive thing you can pour into your hot tub. No product on any shelf for any price will solve all the water chemmistry problems faster or cheaper than dumping the whole mess down the drain and starting over.

If it costs more than three bucks to fix it...
Just chuck the whole mess down the drain and start over

Everything you pour into a hot tub stays there until you drain it. When you get to the bottom of a 2 lb container, there are two additional pounds of 'stuff' in the water.

This stuff builds up as chemical byprodcuts that eventually cause unintended chemical reactions. As byproducts build up, water chemistry becomes difficult or impossible to manage.

Even if chemistry can solve a problem, it sometimes takes several doses over several days to get the job done. How much is your time worth compared to a $3.00 batch of water?

Fix it With Filtration First

Just because you can fix a problem with chemistry doesn't mean you should. Every ounce of product you pour into the water stays there until you drain it all out and replace it with fresh water.

Over time, chemical byproducts build up to levels that cause undesireable chemical reactions. Adding more chemistry just adds more byrpoducts and makes the problem worse.

Buildup of byproducts can make it impossible to balance pH or adjust Alkalinity. It can also cause skin irritation and is the source of that caustic, choking vapor that indicates a batch of water is long past it's useful lifespan.

If you can fix a problem with filtration first;
You can avoid chemical buildup.

Your hot tub came equipped with a filtration system capable of removing micoroscopic particles from the water without adding a single tablespoon of chemistry.

Most hot tubs allow you to adjust the filtration cycle from a typical minimum of 2 hours per cycle up to 24-hour continuous filtration.

When you have a water quality issue like cloudy or oily water, try increasing filtration time and run one or two filtration cycles before resorting to chemistry.

If you keep chemistry to a minimum and fix problems with filtration first, you get more miles-per-gallon out of every batch of hot tub water.

CAUTION: Running a 24-hour filtration cycle for prolonged periods may cause your hot tub to overheat espeically in hot weather. The residual heat from the electric motor can gradually increase the water temperature even after the heater has turned off.

Monitor water temperature whenever running extended filtration cycles. If necessary, lower the set temperature to disable the heater and open the cover to vent excess heat.

It's Not a Swimming Pool
(It doesn't need a 'daily dose')

An open, uncovered swimming pool is basically a man-made pond. Every day dust, pollen, bugs, bird droppings and other debris fall out of the sky or otherwise find a way to contaminate the water.

An uncovered swimming pool needs a daily dose of sanitizer (i.e., Chlorine) to compensate for this daily load of contamination.. Without sanitizer, an open swimming pool quickly becomes a swamp.

Sunlight breaks down sanitizer and evaporation makes even more disappear into thin air so an open swimming pool uses up sanitizer every day even if the water is clean and nobody swims in the pool.

A floating tablet dispenser works in a swimming pool because the daily load of contamination needs a daily dose of sanitizer to keep things clean.

A portable hot tub is more like a sealed water tank and does not need a daily dose of sanitizer unless the tub is used daily.

The insulating cover is normally on the tub unless you're sitting in it so there is no dust, pollen or debris and no sunlight or evaporation to deplete the sanitizer (i.e., Chlorine or Bromine).

A covered hot tub is more like sealed tank than an open swimming pool...

If everything is clean and sanitary when you put the lid on, a hot tub does not need additional sanitizer unless it becomes contaminated.

A clean, covered hot tub only becomes contaiminated when you sit in it. If you don't sit in the tub every day, it does not need a daily dose of sanitizer.

A floating tablet dispenser works well in a heavily used hot tub with a daily bather load like at a holtel or health club. However, the dispenser will release a daily dose of Chlorine or Bromine whether the hot tub needs it or not.

If you don't use your hot tub every day, the floating dispenser can quickly overose your hot tub with Chlorine or Bromine.

Mismanaged floating tablet dispensers are the leading cause of hot tub chemical damage.

If you use a floating tablet dispenser you must remember to adjust the output or remove the dispenser entirely during periods of nonuse.

See Chlorine / Bromine Floating Tablet Dispenser Instructions for more information.

Bather Load is the Biggest Variable

Everybody who jumps in a pool or climbs in a hot tub brings with them a certian amount of perspriation, sweat, body oil, dead skin and other 'organic contamination' that stays behind when you get out of the water.

This contamination is called 'bather load'.

In a typical backyard swimming pool, the bather load of a single person is diluted in about 15,000 gallons of water so the ratio of bather load to water is 1: 15,000.

In a typical residential hot tub, the batherload of a single person is only diluted in about 400 gallons of water so the ratio of bather load to water is only 1:400. This means you get a lot more contamination-per-gallon in a hot tub.

The water in a hot tub is also much hotter than a swimming pool so bathers perspire a lot more and the hydro-massage of jets also scrubs off more dead skin, body oil and other organic stuff.

The bather load of two people sitting in a 400 gallon hot tub is about the same as 75 people swimming in the average backyard pool.

That's why a hot tub can go from crystal clear and sparkling to a milky gray, murky mess in just a single afternoon. You get a lot more yuks-per-gallon in the smaller volume a hot tub.

Products You Probably Don't Need

Unless you own a private well, the water pouring out the end of your garden hose has already been processed and treated to meet state and federal drinking water standards.

When you fill a hot tub with a fresh batch of water, it has already been filtered to remove microscopic particles, sanitized to remove bacteria and other microorganisms and pH balanced to protect all the expensive infrastructure (underground pipes) it takes to get water to your home.

A fresh batch of water should only need minor adjustments because most of the work has already been done by your local water district.

Every water district must publish annual reports on water quality which is a great place to learn more about the local water suppply and what you really need to put in your hot tub.

You can find your water district and their water quality reports here:


How much money is sitting at the bottom of your hot tub?

A typical 'start-up kit' comes with every product you might need for a worst-case scenario. Unless your water comes from a well (or a creek), you probably don't need most of the stuff you've been told to add every week.

Using products you don't need is more than just a waste of money. It's a waste of water because your tub builds up unnecessary byproducts and you'll have to drain it sooner than later. The more stuff you dump in: The sooner you'll have to dump it all out.

Everything you add to the water becomes part of an ongoing chemical reaction. Adding more stuff makes the chemical reaction more complicated which makes water balance harder and harder to maintiain.

Every unnecessary dollar you pour into a batch of hot tub water is just money that eventually goes down the drain.

Overdosing chemistry is also the leading cause of expensive hot tub chemical damage.

Metal inhibitor:

Unless you have rust stains in all your sinks, toilets and bathtubs and all your white laundry has a rust-orange tint, you probably don't have enough Iron in your water to leave stains on your plastic hot tub.

If you don't have any blue/green stains in the house, you don't have enough Copper in your water to worry about either.

Metals in the fill water pose very little problem in a hot tub made almost entirely of non-porous plastic. Here in San Diego, most rust stains in portable hot tubs come from lower grades of not-so-stainless steel used for jet trim rings and handrails built into the tub.

Most metals in the water come from older, corroded pipes within the home itself.

(Attn: Blonds - Chlorine does not turn your hair green. Chlorine can burn the blue right out of blue jeans so it will bleach the dye right out of any hair color that comes from a bottle.

Got green hair? Just look at a corroded penny and you'll see the same shade of green which tells you Copper is the culprit. (Maybe they should sell metal inhibitor at salons instead of hot tub stores?)

Alkalinity increasing products:

Don't buy baking soda at the hot tub store.

Read the label on just about any bottle of alkalinity increaser and you'll probaably see 'Sodium Bicarbonate' (a.k.a. baking soda).

Baking Soda increases Total Alkalinity and pH in swimming pool and hot tub water. When Total Alkalinity is properly adjusted, pH will often self-correct so products like pH increaser or decreaser are not needed.

You can buy a 12 lb bag of name-brand baking soda for around $5.00. It even comes with instructions for balancing swimming pool water chemistry but you'll have to divide the swimming pool dosage chart down to the water volume in your hot tub.

If you kept the empty bottle of hot tub 'alkalinity increaser' you can skip the math. Just refill the bottle with baking soda and use the handy hot tub dosage instructions on the back label.

Water clarifier: (the blue stuff)

If you've balanced the water, increased filtration time, increased sanitizer and the water is still can buy a bottle of this stuff and it will fix it like magic...temporarily.

Water clarifier is a flocculating agent which just means it clumps stuff together. When your water becomes dull and loses that sparkle it's often caused by a buildup of contamination particles so small the filters can't catch it.

The flocculating agent attracts the particles creating larger clusters the filters can catch and remove from the water. If you don't remove and clean the filters right away, the floc can break down and release the particles back into the water.

A bottle of the blue stuff can make water bright and clear but adds additional byproducts and s a lot more expensive than a $3.00 batch of water.

Stop the War on Water. If you spend more than two or three days trying to recover a batch of water just dump it out and start over. Your time is worth more than $3.00.

Stain or scale inhibitor: (the green stuff)

The water here in San Diego is often high in pH, Alkalinity and Calcium Hardness but unless you develop a gritty, sandpaper-like deposit on the shell of the tub or have white, crusty build up around faucets and fixtures in your probably don't need this.

Scale forms faster in hot water but only after the water has reached saturation. Saturation happens when the water is so overloaded with chemistry some of reverts back to a solid state and precipitates out of solution.

Scale in a hot tub will typically coat the heat element and cause it to fail prematurely. I've pulled hundreds of heat elements out of tubs as old as 15 and 20 years located all over San Diego County and very rarely see any scale build up.

The element above is coated with scale but it's 15 years old and the owner was using Calcium Hypochlorite. Cal-Hypo is a form of Chlorine appropriate for some swimming pools but all the Calcium byproducts can form scale quickly in the hotter water and smaller volume of a portable hot tub.

If you dump the water on a regular basis and use a 'less-is-better' approach to hot tub water chemistry, you should never reach saturation and should never have problems with scale buildup.

Foam inhibitor:

Foamy water can be caused by pH and Alkalinity issues, body oil and lotions. This kind of foam is usually less than an inch tall, only comes up when the water is agitated, and mostly disappears as soon as you turn off the jets.

In extreme cases, the water may display a 'carbonic reaction' that looks like you filled the tub with Alka-eltzer®. This is one of those unintended chemical reactions that only happens when the water is oversaturated with chemical byproducts and long overdue for a drain & refill.

[insert video of carbonic reaction]

However, if the foam looks like soap's probably laundry detergent. This kind of foam is usually tall and may even overflow the sides of the tub when the jets are running. It will also linger on the surface long after the jets are turned off.

If the foam in your hot tub looks like Mr Bubbles®; It's probably laundry detergent.

The material in some bathing suits can hold detergent through a normal rinse cycle and turn any hot tub into themost efficient soap sud machine you've ever seen.

A single squirt of foam fixing stuff will knock down the suds on contact but it doesn't actually solve the detergent problem. It just puts a layer of silicone on top of the water so the suds can't break the surface. Jet action eventually forces this floating layer to the edges of the tub where it forms a 'hot tub ring' you'll eventually have to scrub off.

You can avoid soap foam entirely by rinsing bathing suits twice when washing them (or just not wearing them) and rinsing filters thoroughly after cleaning them..

You can burn the soap out of a hot tub by adding enough Chlorine or Bromine or non-Chlorine shock but once you get soap in the tub the best way to solve the problem is to dump it all out and start over.

'Fixing' soap contamination with chemicals can be done but leaves a lot of byproducts in the water.

If it foams like soap and smells 'April Fresh' you can always throw your dirty laundry in the tub but it's probably best to just dump it out and start over:

Marketing of Magic Potions:

Every season a new wave of products hits the hot tub market with promises of solving problems you didn't even know you had.

If you have shopped the big box hardware stores you may have learned the people in the garden center know a whole lot about composted steer manure but don't know dirt when it comes to hot tub chemistry.

The best money-making machine in any supply store is the water sample testing station that prints out exactly what you should buy based on a sample from your hot tub.

Nobody ever argues with the printer and nobody seems to notice the whole water test system and the printed results are provided by the hot tub chemical manufacturer.

If you have shopped multiple hot tub supply stores you may have noticed just about every sales person can tell you what you are doing wrong and why their products will solve all your water woes. This is how people end up with a box or cabinet full of miscellaneous, expired hot tub chemistry.

Here is an inside-look at how a product makes it to that wall-of-chemistry:

What does this product do?

  • Cleans something
  • Makes a huge difference in retail sales
  • Makes spa season more profitable
  • Rescues your watercare business
  • Gives you exclusinve territory (if you buy enough product)
  • Enforces Minimum Advertised Pricing (MAP)
Is it any wonder the sales person really, really, really recommends this particular potion for solving your particular problem?


  1. When in doubt: Drain it out. Water is the cheapest thing you can pour into your hot tub. Nothing fixes every water quality problem faster than dumping the whole mess down the drain and starting over. Even in drought, the water in your hot tub has been recycled more than any other drop in your house. Draining your hot tub as needed is not a waste of water.

  2. A covered, portable hot tub is more like a sealed tank than an open swimming pool. It does not need a daily dose of sanitizer unless it has a daily bather load. Chemical overdose is a waste of money and the leading cause of expensive chemical damage.

  3. If you dump more stuff in the water the chemical reactions become more complicated and the water becomes much harder to manage. Most of the stuff on the shelf is designed to solve a specific problem. If you don't have that specific problem, you don't need to add that particular stuff. Use a 'less-is-better' approach to get the most mileage out of every batch of water.

©Affordable Hot Tub Repair, 2014