Maintaining water quality in your ice bath

Cold water immersion delivers real, measurable benefits — but only when the water itself is clean, balanced, and properly maintained. This guide covers what good water care looks like in practice: the chemistry to monitor, the systems that keep water safe, and how maintenance requirements shift depending on how intensively the bath is used.

Why Water Quality Matters More Than Most People Expect

An ice bath holds a relatively small volume of water — often between 500 and 800 litres — that is used repeatedly by one or more people. Each session introduces organic matter: sweat, body oils, dead skin cells, and trace contaminants from the skin's surface. Over time, without proper treatment, this creates conditions where bacteria can proliferate and water chemistry becomes unstable.

Poor water quality doesn't just create hygiene concerns. It can also accelerate corrosion of the bath vessel and components, reduce the effectiveness of sanitisation systems, and create an unpleasant experience that discourages the consistent practice that makes cold therapy effective.

Poor water quality doesn’t only create hygiene concerns. It can accelerate corrosion of the stainless steel vessel and components, reduce the effectiveness of the sanitisation system, and create an unpleasant experience that discourages the consistent practice that makes cold therapy effective.

Understanding Water Chemistry

Across both the System range baths (residential) and System Pro range baths (commercial), Fjord baths monitor two core water chemistry parameters: pH and ORP. Understanding what these measure makes water management considerably more intuitive.

pH (Acidity/Alkalinity)

pH measures how acidic or alkaline your water is on a scale of 0 to 14. For a Fjord bath, the target range is 7.2 to 7.6 — slightly alkaline. Water that drifts below this range becomes increasingly acidic, which can irritate skin and eyes and accelerate corrosion of the stainless steel inner vessel. Water above 7.6 reduces the effectiveness of sanitisation, allowing contaminants to persist even when the system is running correctly. Keeping pH within range is the foundation on which everything else depends.

ORP (Oxidation-Reduction Potential)

ORP is expressed in millivolts (mV) and measures the sanitiser’s ability to oxidise and neutralise contaminants — in practical terms, it is a real-time indicator of how effectively the water is being disinfected. The target range for Fjord baths is 650 to 780 mV. Higher values indicate stronger disinfection capacity; readings that fall consistently below this range signal that sanitiser effectiveness has dropped and the bath should not be used until the cause is identified and resolved.

ORP is a more reliable indicator of water safety than measuring free chlorine alone, because it reflects actual disinfection performance rather than the presence of a chemical. It is the reason Fjord’s auto-dosing system monitors ORP continuously rather than simply dosing on a timer.

Free Chlorine

For System Pro baths where the HANNA BL120 auto-doser is managing water chemistry, the target free chlorine level is 1 to 2 ppm. This is the residual chemical sanitiser maintained in the water to support the ORP reading and provide an additional layer of protection. The BL120 uses liquid chlorine (sodium hypochlorite) — never tablets, granular chlorine, or stabilisers, which can interfere with the dosing system and cause water balance issues.

Total Alkalinity and Calcium Hardness

While pH and ORP are the day-to-day indicators, total alkalinity and calcium hardness are important supporting parameters that a qualified pool technician will test during periodic servicing. Total alkalinity acts as a buffer for pH, resisting sudden shifts and making the water easier to keep in balance. Calcium hardness affects how water interacts with metal and plastic surfaces. Water that is too soft becomes aggressive and can accelerate corrosion over time. These parameters do not change rapidly, but they need to be checked and corrected periodically to maintain the overall health of the system.

What Changes Water Chemistry

Understanding what drives chemistry shifts makes maintenance more intuitive and less reactive.

• Body load: Every person who enters the bath introduces sweat, body oils, and organic compounds. These are the primary driver of ORP depletion and bacterial load. A bath used by multiple people daily demands meaningfully more active management than one used by a single person a few times per week.
• Ambient temperature and UV exposure: Outdoor baths exposed to sunlight experience faster chlorine degradation. High ambient temperatures accelerate bacterial growth and chemical depletion.
• Source water quality: The town water used to fill the bath carries its own chemical profile. Chlorine levels, mineral content, and pH will all vary by location and season. Hard water areas introduce higher mineral loads from the outset, affecting both balance and TDS.
• Bather hygiene: Showering before use significantly reduces the organic load introduced to the water. In commercial settings, this should be a clear expectation for all users.

Sanitisation Options

UltraZone UV and Ozone

UV and ozone systems are the most sophisticated approach to water sanitisation for residential and light commercially used ice baths, and they are increasingly the standard for well-designed products on the market. 

A UV system passes water through a chamber where ultraviolet light destroys the DNA of bacteria, viruses, and other microorganisms, rendering them unable to reproduce. Ozone works similarly. Generated on-site, it is introduced into the water where it oxidises and neutralises contaminants before breaking down into harmless oxygen.

Used together, UV and ozone provide broad-spectrum sanitisation with minimal chemical input. They are well-suited to residential baths and light commercial use environments where water is changed regularly and the organic load is manageable. They create a noticeably cleaner bathing experience, with none of the chemical odour associated with traditional sanitisers.

Additional chemical treatment is optional and supplementary for UV and ozone systems. on this model, not the primary sanitisation method. During periods of heavy use an oxygen-based shock treatment (Oxy Shock) can be added to oxidise contaminants such as PRODUCT that the UV and ozone system may not fully address on its own. A low but consistent residual of spa sanitiser such as PRODUCT can also be maintained to support the UV system between circulation cycles. Always dissolve chemicals in a separate container with water before adding to the bath — never add directly to the bath water, as this can corrode the stainless steel.

Fjord's system range for residential or light-commercial use baths uses UltraZone UV-C and ozone sanitisation. 

Chemical Auto-Dosing

For high-use commercial environments such as wellness studios, gyms, recovery centres, and hospitality facilities, UV and ozone alone may not be sufficient. 

Chemical auto-dosing systems continuously monitor water chemistry and dispense precise amounts of sanitiser and pH adjuster in response to real-time readings. This removes the reliance on frequent manual testing and human timing, ensuring that chemistry stays within target ranges regardless of how the bath is being used. In demanding environments, this consistency is the difference between reliable hygiene and preventable problems.

Filtration: The Mechanical Foundation

Sanitisation and chemistry management get most of the attention in water care discussions, but filtration is the mechanical foundation that makes everything else work. A filter physically removes suspended particles from the water — skin cells, body oils, dust, and organic debris — before they break down into compounds that challenge your sanitisation system. Without effective filtration, even a well-dosed bath will gradually cloud and develop an odour that no amount of chemical adjustment will resolve.

Filter Types

Most ice baths use cartridge-style filters. These are pleated polyester or fibreglass medium housed in a canister through which the circulating water passes. The quality and size of the filter matters considerably. Undersized filters, or those designed for general water flow rather than bathing water, reach capacity quickly and require more frequent cleaning to maintain adequate flow rates and water clarity.

Spa-grade cartridge filters — the standard used in quality hot tubs and commercial aquatic environments — are the appropriate specification for an ice bath. They offer significantly greater surface area than generic alternatives, handle higher flow rates without pressure drop, and are widely available from multiple suppliers, keeping replacement costs predictable.

Fjord baths use XL spa-grade 50 sqft filter cartridges [link]. 


The spa-grade filters used in any Fjord System or System Pro ice bath. 

Cleaning Your Filter

A filter should be rinsed with a garden hose and ideally a cleaning attatchment such as PRODUCT every two to four weeks under typical residential use, and more frequently if the bath is used daily or by multiple people. When rinsing, work from the top of the cartridge downward, directing water between the pleats rather than across the surface. This dislodges trapped debris rather than compacting it further into the medium.

Every one to three months, a deeper clean with a dedicated filter cleaning solution such as PRODUCT is worthwhile. These products break down the oils and organic compounds that a water rinse cannot remove — the same body oils and residues that coat the filter medium over time and reduce its effective surface area. Soak the cartridge overnight, rinse thoroughly, and allow it to dry completely before reinstalling if a spare is available.

Replacing Your Filter

Even with regular cleaning, filter cartridges have a finite service life. The pleated medium degrades over time, losing its ability to trap fine particles effectively. As a general guide, plan to replace the cartridge every three to six months in residential use, and every two to three months in commercial or high-use environments.

A useful indicator that replacement is overdue: if the cartridge no longer responds to cleaning — water clarity remains poor or flow rate stays low despite a thorough rinse and soak — the medium is spent. Continuing to run an exhausted filter places additional load on the pump and reduces the effectiveness of the entire water treatment system. Worst case, an exhausted filter reduces the movement in the water, which can create corrosion of the stainless steel over time. 

Keeping a spare cartridge on hand is a simple habit that pays dividends. It allows you to swap and clean without any interruption to the bath’s operation, and it removes the temptation to defer a replacement because a new filter has not yet arrived.

Fjord baths are fitted with XL spa-grade filters sized for high-capacity water management. Replacement filters can be found here. [LINK]

Testing and Monitoring

For residential baths used a few times per week by one or two people, a standard test strip checked two to three times per week is adequate. Test for pH, sanitiser level, and alkalinity at minimum.

For commercial baths, the general check should be completed at opening, mid-shift, and close as a minimum, or every two to four hours under high use. Each check includes verifying water level, confirming circulation, reading pH and free chlorine via test strips or a handheld tester, and confirming the auto-dosing controller panel shows pH 7.2 to 7.6 and ORP 650 to 780 mV with both pumps on Auto. Record every result in the maintenance logbook. Trends over time are more informative than any single reading, and a logbook is also a regulatory requirement for commercial facilities.

For busy commercial environments, a digital or handheld water tester provides greater accuracy than test strips and removes the ambiguity of colour-matching. Cross-referencing handheld readings against the auto-doser controller is good practice and will alert you early if the inline probes are drifting and need calibration.

Practical Maintenance Habits

• Test water chemistry two to three times per week at minimum for residential use, and daily in commercial settings.
• Encourage users to shower before entering. In commercial spaces, make it a non-negotiable policy.
• Keep a maintenance log. Tracking chemistry over time reveals patterns and helps you anticipate issues rather than react to them.
• Replace filters on schedule. A clean filter is fundamental to water clarity and reduces the work the sanitisation system has to do.
• Monitor source water quality seasonally. Municipal water chemistry can shift between seasons, which affects how you balance the bath.
  

Water care is not complicated when approached systematically. The goal is consistency rather than perfection at any single test. We recommend focusing on building a consistent, well-managed environment and routine that supports safe and clean immersion every time.