Frequently Asked Questions


Hot Tub Care & Maintenance

How often you clean out the ash depends on how often you use your hot tub. For infrequent users, once a month should suffice; for frequent users, we recommend clearing out the ash once a week. Use a shovel to remove the ash.

At a minimum, your hot tub water should be treated with both a sanitizing agent (bromine) and an oxidizer (also called “Shock”). The sanitizer will kill bacteria, keeping your water clean. Shock oxidizes your water, giving the sanitizer a boost as well as helping remove organic contaminants from the water.

Although a common choice for other pools and spas, we do not recommend using chlorine to sanitize your tub or using chlorine / tri-chlor-based Shock to oxidize your tub. Chlorine is harsh on the wood and will lead to faster decay of the wooden components. Further, if you have a wood-fired tub, chlorine can lead to corrosion of the hot tub stove.

Bromine is gentler on the skin and has a less powerful odor. Bromine also has a lower pH level than chlorine and therefore it can be easier to keep your water pH balanced when using bromine.

Redwood Outdoors sells a Bromine Cleaning Kit with everything you need to keep your hot tub sanitary, including SpaGuard bromine tabs and SpaGuard enhanced shock. The kit also comes with a floating bromine dispenser and testing strips for checking your bromine levels.

NEVER mix chlorine and bromine either dry or in the hot tub water as this can cause a dangerous reaction. If you are considering switching from one sanitizer to another you should always first clean and drain your hot tub including a plumbing line flush.

Regularly check the bromine levels within your hot tub (i.e., multiple times per week) to make sure your water is sanitary. We recommend maintaining a bromine level of 3ppm (or slightly lower). This is at the low end of the typically recommended level for a plastic spa (3 - 5ppm). The reason for this is to better preserve the wood. At higher concentrations, bromine, like chlorine, can be harsh on the wood. Color-coded test strips are available that easily test the concentration of bromine (and other chemicals) in your hot tub.

To add bromine to your tub, we recommend using a floater which will distribute chemicals evenly. Putting tabs directly into the tub so they sit on the bottom is not recommended as this will damage the liner. There should be a floater with bromine tabs floating in your hot tub at all times. After adding new water, use approximately 1 bromine tab per 100 gallons (always refer to the product label for the manufacturer’s specific directions).

In addition to bromine, use 3 tablespoons of Shock per 500 gallons of water. If you are using bromine, be sure that the Shock you are using is not chlorine or tri-chlor based. If you are tubbing less than 4 times per week, add Shock once per week. If you are tubbing every day, add Shock twice per week. These are general guidelines and you should always refer to the product label for the manufacturer’s specific directions.

After adding Shock, leave the hot tub for at least 30 minutes with the cover off before using the hot tub again.

Yes. Keeping your water sanitary is not enough to maintain your hot tub. It is also very important to monitor your alkaline, pH, and calcium (hardness) levels to avoid damaging your hot tub and electric equipment.

Any damage to the equipment or the hot tub due to improper water maintenance is not covered under Redwood Outdoor’s product warranty or 3rd party equipment warranties.


Alkaline acts as a “buffer” in your water to changes in pH level. Alkaline is measured in ppm. The recommended range for alkaline is 80 - 120 ppm. If your alkaline levels are too low, this can lead to pitting / etching in your wood or liner, sudden changes in your pH level, and corrosion of any metal in your hot tub. If your alkaline levels are too high, this can lead to scaling on the equipment, more particles in your water leading to clogged pipes / filters, and “pH lock” (i.e., inability to change the water’s pH).


pH is the acidity of your water. pH is measured on a relative scale from 0 - 14, with 0 being most acidic, 7 being neutral, and 14 being not acidic at all. The recommended range for pH is 7.2 - 7.8. If your pH level is too low (i.e., <7.2; too acidic), your sanitizer will not work, this may result in bathers having an itchy burning sensation on their skin and eyes. addition, acidic water seriously damage equipment. if ph level is high (i.e.,>7.8; not acidic enough), your sanitizer will stop working and you will have cloudy water with lots of particles in it.

Calcium (Hardness)

Dissolved calcium is naturally present in most water. Calcium is measured in ppm. The recommended range for calcium is 150 - 250 ppm. If your calcium levels are too low, this can lead to corrosion on your equipment (electric heater, stove, and even cover), your water may also be abnormally foamy. If your calcium levels are too high you will get scaling, which will block your pipes and damage your equipment over time.

In most cases, when balancing your water you will find that you need to increase your alkalinity, decrease your pH, and increase calcium. Our Water Balancing Kit provides the chemicals needed to make these adjustments as well as test strips so that you can check the levels in your water. These test strips also come with our Bromine Cleaning Kit.

If you find that your water needs to be adjusted differently (e.g., if you need to decrease your alkalinity), SpaGuard also offers chemicals to make these adjustments which can be sourced from any pool and spa store.

If you are filling your hot tub for the very first time, you should perform two checks before you add any chemicals.

1. Check the calcium level (this can be done with a test strip). If your water’s calcium is naturally >250ppm, it is not recommended for use in your hot tub. We recommend filtering your water to reduce the calcium or using a different water source.

2. Check your water for levels of metals. This cannot be tested with typical home kits and we recommend bringing a sample to a pool and spa specialist shop for testing. They can also recommend solutions if your water does contain metals.

Once you have confirmed that your water source is suitable and you are using it in your hot tub, regular water balancing can be done in three steps:

1st: Test your alkaline levels and adjust to within the recommended range.

2nd: Once the alkaline levels are between 80 and 120ppm, test your pH levels and adjust to within the recommended range.

3rd: Once your pH is between 7.2 and 7.8, test your calcium levels and adjust to within the recommended range.

It is important to adjust levels in this sequence because they will influence each other, if you switch between testing pH and alkaline you may never get either into the correct range.

Wood-Fired Hot Tubs

Our wood-fired hot tubs do not have circulation or filtration systems. This means that even with chemical treatment, the hot tub water needs to be changed regularly. We recommend that our wood-fired hot tub customers change their hot tub water every 2-3 weeks, depending on usage. It is especially important that you take a shower to clean off before using an off-grid hot tub, as this will help extend the life of your water.

Electric Hot Tubs

Our electric hot tubs have circulation and filtration systems. Circulating the water through your hot tub’s filter cartridge helps keep it free of contaminants. In order for this to work as intended, the pump and filter should be operated for at least 3 hours every day whether the spa is used or not. Circulation and filtration mean the water can last much longer before it needs to be changed. Electric hot tub owners should change their water approximately every 3 months, depending on usage.

If you have an electric hot tub, the filter cartridge needs to be regularly changed to keep the filtration system working effectively. A filter cartridge typically lasts ~12 months, however, the filter cartridge must be cleaned regularly to achieve this lifespan.

To keep your filtration system in top working condition, we recommend cleaning it once per month. To clean the filter cartridge, remove it from the filter and place it in a bucket of water. Add a cleaning agent to the water and swish around to mix. Let the cartridge sit in the bucket for ~24 hours. After 24 hours, take the cartridge out, rinse, and leave it to dry. Once the filter is dried out, you can put it back in the filtration system for use.

We recommend customers buy filter cartridges in pairs. Then when it's time to clean your filter, you can use your second cartridge. By rotating between filter cartridges, you can avoid having to stop using your hot tub while the filter is being cleaned and you can buy cartridges less frequently.

Weekly Maintenance Checklist

• Check your bromine levels and add bromine tabs if needed.

• Add Shock (Oxidizer).

• Check the water’s alkalinity, pH, and calcium. Adjust if any of the levels are out of the recommended range following the sequence above.

• Clean above the waterline. Wipe away the debris that might contaminate the water and throw off the chemical balance.

Monthly Maintenance Checklist

• Clean your hot tub filter (if you have an electric hot tub).

• Change your water (if you have a wood-fired hot tub). This might need to be done bi-weekly depending on your usage pattern.

Quarterly Maintenance Checklist

• Change your water (if you have an electric hot tub).

Annual Maintenance Checklist

• Drain your hot tub and hose down the interior with fresh water. Gently scrub the liner / benches with a soft-bristled brush and soapy water. Never use harsh chemicals such as bleach to clean your hot tub.

• Flush and clean your plumbing lines (if you have an electric hot tub).

If you are using your tub with a liner, you can leave your tub empty for an extended period. Some customers will drain their tub and leave it empty over the winter if they do not plan on using it.

If you are using your hot tub without a liner, we do not recommend leaving your tub empty for more than a few hours. This is because the wood can change shape when it drys, and when it swells up again, it may not seal. If you plan on draining your tub to change the water, we recommend refilling it as soon as possible to make sure the wood remains damp and does not change shape.

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