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Chlorine-free hot tub maintenance with GUAa: a complete step-by-step guide
Chlorine is the most common way to keep your hot tub water fresh — but it's also the reason why some people's hot tubs "smell like a pool," irritate their eyes or skin. Chlorine-free active oxygen maintenance is a convenient alternative: it keeps the water fresh by oxidizing impurities, without the chlorine smell. In this guide, you'll find the exact procedure with the Czech system GUAa OxiSystem, which we keep in stock in the e-shop — including what active oxygen can't do and how to fix it.
How GUAa OxiSystem works
The system has two components that complement each other:
- GUAa OXI — active oxygen (based on potassium oxygen salts). It oxidizes organic impurities in water — sweat, cosmetics, skin oil — i.e. „food“ that would otherwise spoil the water. It works quickly: you can swim an hour after application.
- GUAa WHIRLPOOL — additional water care product: helps evenly disperse substances in the water column, limits the formation of a surface film on the surface and reduces dirt deposits on the walls of the tub.
Honestly, what this system is not: active oxygen is oxidation, not sterilization of water. Therefore, for chlorine-free maintenance, we recommend UV-C lamp (with GUAa it is fully compatible — we have it in stock), consistent filtration and regular water changes. It is precisely in this combination that chlorine-free operation makes sense — and that is exactly how we build it into our hot tubs.
Commissioning (new filling)
- Clean the bathtub mechanically to remove deposits and limescale (it will help when changing the water). SPA DECALCITE).
- Fill and turn on the filter circuit.
- Edit pH to 6.8–7.4 (drop tester + pH Minus/Plus). Attention: for GUAa, the target pH is slightly lower than the usual 7.2–7.6 — OXI acts acidic, the system is built for that.
- Apply OXI: 50 g per 1 m³ of water with filtration turned on (dissolve in a bucket of warm water and pour over the surface).
- After 12–24 hours add WHIRLPOOL starting dose: 250 ml per 1 m³.
- After mixing, the hot tub is ready; after 7 days, proceed to regular maintenance.
Weekly routine (repeat every 7–14 days)
Step: 1
What: Measure and adjust pH (check every 2–3 days in summer)
Dosage per 1 m³: target 6.8–7.4
Step: 2
What: OXI on the surface with filtration and nozzles on
Dosage per 1 m³: 50 g
Step: 3
What: After 12–24 hours WHIRLPOOL directly into the bathtub
Dosage per 1 m³: 100 ml
Step: 4
What: Rinse the filter cartridge
Dosage per 1 m³: —
Practical tip: a level cap of OXI can ≈ 100 g. For a regular hot tub with a volume of ~1,100 l, the following applies: half a cap of OXI per week + ~110 ml of WHIRLPOOL. If the water foams after a party, a defoamer will help (10 ml/m³ as needed).
Annual maintenance plan
Rhythm: Daily/every other day
What to do: visual inspection of water; in summer pH every 2–3 days
Rhythm: Weekly (7–14 days)
What to do: pH → OXI → after 12–24 h WHIRLPOOL; rinse cartridge
Rhythm: Monthly
What to do: alkalinity control (target 80–120 mg/l), deep cleaning of the cartridge (SPA CLEAN FILTER)
Rhythm: 3–4 months
What to do: cleaning the circulation circuit (before draining, on a full bath: add the product to the circuit, swirl for ~10 minutes, drain, rinse) → complete water change → descaling → refilling with starter dose
Rhythm: Seasonally
What to do: filter cartridge inspection/replacement (every 3–5 months), technology review — We will be happy to help with service.
Filtration: 2–3 shorter cycles per day so that each one filters the entire volume of water (time = volume ÷ filtration capacity). Filter more when you are away — stagnant water spoils faster.
What to never do with GUAa
- Do not mix with chlorine or bromine. The manufacturer explicitly warns: GUAa preparations must not be used together with chlorine-based products.
- Do not combine with a salt system — electrolysis produces chlorine, see previous point.
- Don't switch from chlorine to day. Correct procedure: either neutralize the chlorine with OXI (it breaks down within about 30 minutes after mixing), or change 30–50 % of water, or let the circulation run for 1–2 days without chlorine dosing. Use GUAa first 1–2 days after the last chlorine.
- Don't rely on chemicals for a neglected filter. The cartridge is the first line in chlorine-free operation — hence the emphasis on rinsing and cleaning.
Frequently asked questions
What role does GUAa play in water stewardship?
GUAa OxiSystem is a chlorine-free oxidative water care: active oxygen breaks down organic impurities and WHIRLPOOL keeps the water clear and the surface free of film. Strengthen the microbiological protection of the water with a UV-C lamp, consistent filtration and regular water changes — that is exactly how we recommend chlorine-free operation.
How long after dosing can I take a bath?
After applying OXI, an hour with the filtration turned on is enough. WHIRLPOOL is added 12–24 hours after OXI.
Why does GUAa have a different pH than the „swimming pool“ 7.2–7.6?
The system is set to pH 6.8-7.4 — OXI reacts slightly acidic and works best in this range. Stick to the manufacturer's values, not general tables.
How often should you change the water?
For a private hot tub, every 3–6 months (earlier for intensive use); with GUAa, we recommend combining the 3–4 month cycle with cleaning the circulation circuit. In the meantime, releasing a portion of the volume monthly helps.
What if the water becomes cloudy or foamy?
Turbidity: check the pH, clean the cartridge and perform an extra dose of OXI; a clarifier (SPA CLARIFICATION). Foam after intensive bathing: defoamer 10 ml/m³. When nothing helps, it's time to change the water.
Can I use GUAa in a hot tub of another brand?
Yes, the system is not tied to our bathtubs — it is dosed according to the volume of water. However, for hot tubs with their own automatic water treatment (salt, chlorinator), please consult us first; combinations are not possible.
Is chlorine-free operation financially worthwhile?
The costs are comparable to chlorine maintenance (in the order of hundreds of crowns per month depending on volume and usage) — the main benefit is comfort: odorless water, gentle on the skin and eyes. You can calculate the total operating costs in the article How much does it cost to operate a hot tub?.