NSF/ANSI 50 has many specialized tests for assessing filter media, filters, and systems that incorporate filters. Through NSF’s work with the Joint Committee on Recreational Water Facilities, NSF has helped the industry create a multidimensional filter assessment criteria, including testing methods for contaminant loading, treated water volume, and filter media cleaning water needs. This assessment gives valuable insight into filter performance because it is not a singular assessment.
NSF has 55 years of testing products, auditing filter manufacturers, and certifying pool, spa and recreational water products for the industry. NSF’s history of filter performance testing and safety assessment began in 1960 with pre-coat (i.e., DE type) and granular media bed (i.e., sand type) filters. Later, during the 1960s, other product standards were issued for cartridge filters, pumps, skimmers, etc. In 1977, NSF merged all the individual pool and spa equipment standards under one standard number: NSF/ANSI Standard 50. This enabled NSF to better serve the recreational water industry with one balanced group of public health officials, product manufacturers, product user group. Having one group address any and all recreational water facility issues has enabled NSF to perform ongoing development of advanced product criteria.
One example of new product criteria is the Filtration Efficiency testing program that is offered by NSF’s Recreational Water Program. This special testing program enables a manufacturer to obtain independent third-party assessment of important factors of filter performance beyond the traditional NSF/ANSI Standard 50 criteria.
The traditional criteria are:
• Material safety evaluation
• Corrosion resistance evaluation
• Structural integrity, including a 4:1 design burst pressure, 75psi hydrostatic pressure test, 20,000 cycle test of 0-30-0psi and 100psi sustained pressure test, as well as head loss pressure testing, filter media cleanability, turbidity reduction and other requirements.
However, the NSF Filtration Efficiency testing program goes beyond these requirements to enable assessment of filter performance for other variables of water and filtration efficiency.
NSF testing program generates data such as:
• Total dirt-holding capacity of a filter (when dosed with the challenge media)
• Total treated water volume (while filter is run at target rate and being dosed with the challenge media)
• Total water consumed (during backwashing and cleaning cycle after reaching its pressure differential)
In recent years there has been a plethora of new NSF/ANSI Standard 50 criteria for product performance assessment to help all stakeholders ensure they are getting products that meet their technical requirements without limiting product design or innovation.
There has been interest in assessment of filters and pre-filters as being more water efficient, and giving credit to products that perform more efficiently. Some code agencies struggle with product efficiency assessments due to single-attribute evaluation criteria. With ongoing drought conditions, there is demand in the recreational water industry for standardized methods to provide assessment criteria for the water-saving properties of various filtration products and system designs.
NSF/ANSI 50 doesn’t currently include a specific test method to quantify filtration device water efficiency. But NSF has created additional criteria to address this need. The new NSF criteria evaluate parameters such as filter dirt-holding capacity, total water volume treated during a filter run, time required for filter cleaning, water consumption as part of filter media cleaning and provides composite metrics of all values to enable performance rating of filtration systems.
NSF staff developed the criteria as part of the NSF/ANSI Standard 50 Task Group under the Joint Committee on Recreational Water Facilities. It enables a thorough multi-dimensional assessment of filter efficiency.
This criteria will be balloted into NSF/ANSI 50 because of industry participation and because it is the ideal platform for adding and publishing such methods. This new criteria will provide a mechanism for those manufacturers wanting to address growing environmental pressure in the recreational water industry.
The intent would not be to give specific water savings (i.e., company X’s filter saves ___ gallons or company Y’s filter saves ___ gallons), but would be to give a tiered ranking, i.e., Green Level 1, 2, 3 or Gold, Silver, Bronze, etc., that provides a multidimensional assessment of filter performance.
We believe this approach is more technically accurate and would prevent product manipulations.
Criteria would include:
• Total water volume filtered or treated
• Total dirt-holding capacity
• Cleaning or backwashing water consumption
• Can be reported as % efficiency, gallons consumed per 1,000 gallons filtered, gallons used per year, etc.
• Water savings
• A rating scale for filters based on performance metric related to testing
• Cleaning cycle time
• Effect of pre-filter use upon filter cleaning cycle time
It’s important to not focus solely on water consumption during backwashing or filter media cleaning. A single-metric approach neglects other important factors, such as the amount of total water cleaned or filtered (not just how much water is spent during filter cleaning). Facility operators and management also may want to know the overall labor time (to figure cost) for filter cleaning, as well as quantification of dirt-holding capacity. Additionally, aquatics facility operators and industry professionals know that removal and replacement of a portion of pool/spa water is best practice for managing water quality and water chemistry.
Various national and international pool/spa guidelines, such as World Health Organization Guidelines for Safe Recreational Water Environments, Volume 2: Swimming Pools and Similar Environments 2006, recommend pool and spa dilution. Typically, this is achieved via makeup water. For instance, the WHO guideline (and the requirement in some European countries) is 30 liters of water per day per swimmer. Coagulation, filtration and disinfection will not remove all pollutants. Pool design should enable dilution to limit the buildup of pollutants.
This is an important consideration that often is lost in the rush to assess “green” credits by code agencies. They may not have sufficient industry knowledge or understand the value of water changing or discarding of filter backwash that is high in total dissolved solids. High TDS negatively impacts water chemistry and maintenance for aquatics operators. When clean makeup water is added (and some TDS-laden water removed) it enables better water quality for swimmers.
For these reasons, a multiple-variable approach to filtration efficiency is best. The NSF Filtration Efficiency testing program provides a more complete assessment of filter performance to help users find products that save water without sacrificing the critical importance of water filtration and public health.
For more information contact Theresa Bellish at bellish@nsf.org.