Most labs rely on purified water across their operations, making water purifiers integral to a lab’s design, but selecting the best purifier for your lab can be a challenge because of all the factors involved. Water purification methods vary in their technology, output, flow rates, and designs, among other details. Most labs will have multiple or multi-stage water purification systems in place, and systems typically combine multiple technologies to achieve a particular purity level.
What matters most is that the water purification system(s) consistently meets a lab’s needs. Considering the following factors when purchasing can help lab managers achieve that.
What is the required purity level?
Understanding the required purity level for lab water quality can be challenging, given the many terms thrown around. Some may refer to it by standards-based types or grades, purification technique—such as reverse osmosis (RO), deionization (DI), or distilled water—or application, like instrument feed water or molecular grade water.
Several organizations publish lab water standards, including the International Organization for Standardization (ISO), ASTM International (ASTM), the Clinical & Laboratory Standards Institute (CLSI), the American Chemical Society (ACS), and various pharmacopeias and other regulatory bodies worldwide. Which standards to reference depend in large part on field and local regulations.
While these standards are an easy benchmark for reference, determining the water purification for your lab is a more nuanced matter than matching purification grade to process (e.g., “I’m running HPLC, so I need type I water.”). Most standards organizations advise following established application-based specifications, especially for highly sensitive analytical purposes. When used as a reagent or in analytical equipment, labs should always complete fitness-for-use validations.
When choosing a purification system, consider both your unique experimental or process needs and the quality of the supply water. Whether it’s potable water feeding an integrated purification system or pretreated water for further polishing, you will need to know which contaminants of concern for relevant applications are present and their quantity to choose the most appropriate configuration. As with most things in the lab, the quality of what goes in impacts the quality of what comes out. Manufacturers will provide guidelines for feedwater quality—typically including specifications for conductivity, total organic carbon (TOC), and various minerals—for optimal performance. It may not always be possible to meet those specifications or necessary if the final lab water meets the application requirements, though major deviations are more likely to strain the system and require increased maintenance.
How much water does your lab consume?
Depending on the lab, daily water consumption might range from a few liters to thousands of liters. The latter requires high-flow rate water purifiers to keep up with the demand.
When assessing consumption needs, laboratory managers will also need to factor in time and duration of use to ensure adequate supply when the demand is highest. Even a lab with low overall water consumption might need a high-flow water purifier if most of the usage is concentrated at a particular time of day. Alternatively, storage solutions can help ensure demand is met.
Water purity generally degrades during storage due to air exchange, chemical leaching, or biological activity, so it should be checked at the point of use if stored externally for general lab purposes. Water used for analytical or other sensitive applications should not be stored externally—rather, look for systems with built-in storage capable of maintaining quality requirements through recirculation or a combination of features that mitigate contamination. A few considerations for storage systems include:
When assessing consumption needs, laboratory managers will also need to factor in time and duration of use to ensure adequate supply when the demand is highest.
Container material: Contaminants ranging from ions to more complex plastic compounds can leach into the water from contact materials, including metal, plastic, and glass. Higher-purity water extracts ions more aggressively from surrounding materials. Choose systems with high-quality materials compatible with the type of water being stored and the applications.
Stagnation: Purified water will become contaminated with time. The NIH recommends using a circulation loop with ultraviolet light and submicron filtration to hedge against microbial contamination.
CO2 absorption: Water can quickly absorb gases, including carbon dioxide, from the atmosphere. To prevent this, some water purification systems incorporate a nitrogen blanketing system or bag design to fill the headspace with inert gas or remove it altogether.
How often would filters and cartridges need to be replaced?
Filters and cartridges need to be replaced as their performance drops from accumulated impurities. Be vigilant in monitoring water quality for process, analytical, or experimental work, and replace filters and cartridges consistently and according to needs and the manufacturer’s recommendations. Even when reduced performance still meets application needs, delayed maintenance can still put undue strain on the system and affect reproducibility. Consider filter and cartridge costs within the total cost of ownership. Potentially, systems with higher purchase prices and fewer consumables could save you money in the long run.
Are there any space constraints?
As a lab manager, you’re likely all too aware of how precious space is in your lab. Compact and flexible designs for water purification systems that can be wall-mounted or placed in tight spaces can allow a small lab to make the most of its limited space. Other labs may need to install water purifiers around or integrate with existing infrastructure. The type of purification system and storage design will likely need to be balanced between available space and requirements.
Do you need to monitor water quality data?
Labs often need to closely monitor the quality of the output water from their purifiers to ensure consistent results and prevent damage to sensitive equipment like HPLC systems. Most type I and II systems at least monitor a couple of metrics at the dispenser, like conductivity and TOC.
Regulated labs that require monitoring and documenting water quality should also consider connectivity both for real-time monitoring and data transfer.
Regardless of the water purification system you deploy, filters foul, operational efficiency decreases with time, and the cost of ownership is often underestimated. This is why, in addition to these metrics, ease of maintenance and after-sales support should be a major deciding factor.
