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Can I Use Chemicals In A Wood-Fired Hot Tub?

The use of chemicals in the water is common with expensive, electric hot tubs, however this leads to common questions about their use with wooden hot tubs for ease of use.

This post looks at the considerations involved when deciding whether to use chemicals in a wooden hot tub, to ultimately answer the question:  “Can I use chemicals in a wooden hot tub?”.

Before we go on, it’s important to note that traditional wooden hot tubs (those without an internal liner) are not suitable for use with chemicals.  In the case of Royal Tubs, only our fibreglass and lined tubs are suitable for use with chemical water treatment.

Over time, the chemicals will react with the wood, causing grey-scale (where small grey flakes will come off the wood and end up in the bathing water) and ultimately decaying the structure of the wooden hot tub.

Why Use Chemicals In Your Wood-Fired Hot Tub?

In short, using chemicals to maintain water hygiene in your wooden hot tub allows you to keep the same bathing water for longer.

The water in a wood-fired hot tub is not automatically flushed or changed, which means that if the water isn’t changed regularly algae and bacteria will begin to grow, in addition to the contaminants which are added to the water every time it’s used… think shampoo, washing products, sweat, make up etc.  These all build up in the water over time, reducing water quality.

By adding chemical treatment to the water, bacteria and algae growth is prevented (or rather, they’re killed off very quickly).

What Chemicals Can I Use In My Wood-Fired Hot Tub?

There is a wide range of chemicals available for use in hot-tubs, spas and swimming pools.

The most popular options are chlorine and bromine tablets, with chlorine being the most commonly used thanks to its low cost.

There are also a range of less reactive treatments available which claim to be kinder to the skin, such as ionised silver oxidant tablets.

Which Chemicals Are Best For My Wood-Fired Hot Tub?

This question depends on the user.

Many people find that chlorinated water causes reactions such as skin irritation (or “red eye”), and dryness of hair and nails, just as you may find at a public swimming pool.  These effects are actually caused by the by-products of the chlorine breaking down contaminants in the water, and are a sign that the water ought to be refreshed, but parallels are drawn nonetheless.

Bromine is a less-reactive, but more expensive alternative to chlorine.  Many people report bromine treatment being kinder on the skin and hair after spending time in the water.

Silver based treatments are less reactive again than chlorine or bromine, although they are primarily used for the control of algae in the water.

Unfortunately, there’s no simple answer to this question:  it will depend on your own body and the convenience you’re seeking.  It’s also important to note that there is no definitive answer to how often you’ll need to change the water in your hot tub, even if you are using chemicals.  This will depend on factors such as:

  • The frequency of use
  • The number of bathers
  • Any hair or makeup products bathers are wearing
  • Whether people shower before getting into the tub
  • Whether footwear is worn around the hot tub
  • Plus many, many more.

While no chemical treatment will eliminate the need to periodically change the water in your wooden hot tub, using a silver-based treatment can extend the period between changes to around a week (depending on frequency of use), and chlorine or bromine tablets can extend that period a little further, perhaps as much as 10-14 days (again, depending on the use of your tub).

Limitations

Aside from personal safety and your body’s own reaction to these chemicals, the most important factor from a hot tub perspective when using chemicals is the heater.

Wood-fired hot tub heaters directly heat the bathing water, meaning the steel is in constant contact with the water (and hence any chemicals added to it).  

Standard, 430-grade stainless steel is not suitable for use with chemicals in the water.

If you plan to use chemicals to prolong the period between water changes, your heater must be specified in a higher grade steel (304-grade at a minimum, 316-grade is preferred) in order to resist corrosion by these chemicals.

Failure to upgrade the steel, and the use of chemical treatment is guaranteed to cause premature failure of your wood-fired stove, and invalidate the manufacturer’s warranty.

For this reason, it’s highly recommended that you consult with your supplier before purchasing and follow their guidance on the use of chemicals in your wooden hot tub.

Summary

While using chemicals in your wood-fired hot tub adds convenience to its maintenance, it’s not as simple as “throwing a few tablets in the water”.  

Many people enjoy the simplicity of a wood-fired hot tub in part because there is no requirement to chemically treat the water, and the use of such chemicals should not be thought of as mandatory.  Indeed, the majority of wooden hot tub owners enjoy their peaceful retreat without ever using them.

It’s not uncommon for people to react to chemicals differently (which may affect your guests).  All chemicals have the potential to be dangerous, and should be used, handled and stored with the utmost care and diligence.

To sum up, adding chemicals to the water can add a dash of convenience to your tub, but you should discuss this with your supplier and follow all proper guidance when it comes to using them.

Go back Read Next: Why Acrylic Liners Herald The Next Generation Of Wood-Fired Hot Tubs