Understanding DIN standards

by Sally Bouorm | April 1, 2011 11:03 am

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By Dennis Ashworth

When visiting a European aquatic facility, North American operators and designers would likely be in for a few surprises. In fact, when comparing what is acceptable in our region to a minimum European Deutsches Institut für Normung (DIN) standard, the results can be downright shocking.

Some believe Europe is almost 40 years ahead of North America when it comes to public swimming pools and spas, particularly in terms of water clarity, mandatory filtration requirements, disinfection levels and trihalomethanes/chloroform control and testing. In addition, European operators also seem more aware that trihalomethane (THMs), nitrogen trichloride (NCl₃) and other chlorine compounds create risks for both the building envelope and a facility’s bathers and staff. Why these standards haven’t served as a blueprint for the North American pool industry is a question aquatic facility professionals need to ask themselves.

Setting the bar with DIN

DIN is a German national standards organization, known in English as the German Institute for Standardization. Founded in 1917 and operating out of Berlin, DIN currently has more than 30,000 standards in effect, covering all varieties of technology. These standards are available in numerous languages and adopted by many countries or re-written to apply to the countries requirements.

In Europe, DIN is the standard that must be adhered to when a public pool is designed, constructed and equipped. These standards are far stricter than North American equivalents, and tend to result in improved designs and the best possible water quality. The legislation demands quality and provides strict parameters to provide positive results.

This begs several questions: Why is it taking so long to adopt similar requirements in North America? Why is a system that appears to work so well totally disregarded? What do we accept as water and air quality minimums—and why? Is it time for those of us in Canada and the U.S. to re-evaluate our standards with DIN as a guide?

There are several possible reasons North American standards differ so greatly from DIN. One potential reason is that the European scientific community is given greater respect than its North American counterparts. While Canadian and U.S. researchers may be equally skilled and thorough, too often their findings go ignored or unnoticed. In addition, North American manufacturers may have a greater influence on the rules and regulations adopted by governments and testing bodies. In Canada specifically, operators and regulators tend to look to the U.S. as an example; however, 24 U.S. states do not have a pool health act. Standards are often changed to meet the pools, not the other way around. DIN, on the other hand, takes a different approach, one worth investigating in greater detail.

Finessing filtration

The design of the filtration system is critical and mandatory to meet DIN requirements. The depth and design of the filter media provides healthy water returning to the pool. In Germany and Austria, where regulations are strictest, sand is the industry standard, though in a very different form than North American operators are used to.

European-style filtration systems differ from their North American equivalents in many ways, including:

• air release at the top of the filter;
• a clear, wide view port for easy operator inspection;
• pipe connectors located further apart from one another;
• nozzle plate collection (instead of laterals);
• filter bed depth greater than 1,200 mm (47.2 in.) of graded filter media;
• filter backwashing with water and/or water and air;
• diffuser/backwash piping sized to backwash without pressure;
• mandatory use of flocculent; and
• a large freeboard area (open space from the bottom of the diffuser to the top of the sand).

Slower flow rates per square foot are designed to provide superior water quality. The slower the flow, the higher the quality of the filtered water—and slow is good when swimming pool filters are designed correctly.

For filters with higher flow rates up to 667 litres per minute (lpm) per square metre (17 gallons per minute (gpm) per square foot), taller filters with multi-layer, multi-grade media are designed. This provides greater bed depth and extra contact time for flocculation, as well as more freeboard for media expansion during backwash.
If these designs are effective, one might wonder why North American filter manufacturers continue to build horizontal filtration systems with very shallow sand depths (some less than 305 mm [12 in.]). Removing bather waste in a heavily loaded public leisure facility would be nearly impossible at flow rates in excess of 57 litres per 930 cm² (15 gallons per sf); a 1.2-m (48-in.) horizontal filter only provides approximately 610 mm (24 in.) of filter media depth. North American engineers also often specify filters to be able to fit through a typical building door; again, a practical, budgetary concern that does not necessarily reap the most benefits for water quality and user experience
Unfortunately, in North America, price often overrides quality. While these approaches might be healthy for the budget, they do not necessarily provide the safest and most comfortable environment for swimmers.

Important norms and guidelines for pool operation in Europe1
Parameter	Austria	Germany	Switzerland
	BHygG/BHygV	DIN 19643	SIA 385/1
Free chlorine (residual)	0.3 to 1.2 ppm2	0.2 to 0.6 ppm2	0.1 to 0.6 ppm2
Combined chlorine	= 0.3 ppm2	= 0.2 ppm2	= 0.2 ppm2
pH value	6.5 to 7.8	6.5 to 7.8	6.8 to 7.6
Redox potential (ORP)	= 700 mV2	= 700 mV2	= 650 mV2
Aluminum	= 0.1 ppm	= 0.1 ppm	N/a
Trihalomethanes (THM)	N/a	= 0.02 ppm	= 0.02 ppm
Turbidity	N/a	= 0.02 NTU	= 0.02 NTU
(filtred water)
Fresh water addition/dilution	= 30 L/pers./day	= 30 L/pers./day	= 30 L/pers./day
1 To be amended 2011.
2 If swimming pool operates at higher pH levels, higher free chlorine residuals are recommended.

Chart courtesy Wapotec^®

Conquering chlorination

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Poor filtration also leads to another issue—higher chlorine levels. Take, for example, super chlorination and/or shock treatment. In North America, however, many operators still add greater and greater quantities of chlorine into public pools in order to maintain water clarity. In Europe, however, it has been widely accepted that adding more chlorine to a swimming pool will create more problems than it solves. In fact, numerous scientific articles around the world have documented that adding more chlorine produces increased amounts of toxic chlorine byproducts[3] (CBPs). Tests have shown shock treatment can increase THM levels almost instantly by more than 400 per cent.

DIN standards provide not only an upper chlorine limit, but also a maximum reading for free chlorine; in North American jurisdictions, such as Alberta and Ontario, only a minimum level of free chlorine (0.5 ppm) is required by the provinces’ health acts. Switzerland’s SIA standards, for example, are similar to DIN and allow minimum chlorine levels to be as low as 0.1 ppm, with maximum levels of 0.6 ppm.

DIN sets the maximum levels of free chlorine to prevent the formation of CBPs, while up until recently, North American standards have only provided minimum guidelines based on drinking water research due to the lack of information on swimming pool water. The National Swimming Pool Foundation (NSPF), a non-profit organization focused on creating healthy pools and healthy bodies through aquatic education and research, has prompted more studies on recreational water, which looks to improve North American pool and spa water standards.

Differences in free chlorine requirements: Pools1
Ontario minimum	Alberta minimum	European DIN
0.5 mg/L	0.5 mg/L (if oxidation reduction potential [ORP] is more than 700 mV	Minimum of 0.3 mg/L and maximum of 0.6 mg/L

Differences in free chlorine requirements: Spas
Ontario minimum	Alberta minimum	European DIN
5.0 mg/L (if oxidation reduction potential [ORP] is more than 750 mV	2.0 mg/L	Minimum of 0.7 parts per million (ppm) and maximum of 1.0 ppm

Long term health effects

Respect for bathers, especially young children with extremely sensitive upper respiratory systems using public swimming pools and spas, is an exacting science and one that cannot be viewed in isolation without concern for long term health.

Long term contact with CBPs have been well documented and is a subject public swimming pool operators and mangers must make themselves aware to understand the health risks.

Research by Dr. James Amburgey of the University of North Carolina shows that it takes six days for bather waste, deposited by swimmers in the pool’s shallow end, to reach the filters—without aggregation. Most public pool officials worldwide agree that to maintain health pool and spa water, a free chlorine reading of approximately 1 ppm is the right level. However, to achieve this, agglomeration, aggregation, flocculation and coagulation combined with superior filtration (using a deep, multi-layered filter bed and a vertical filter with low flow and pressure) are imperative to improving pool or spa water and the health and safety of patrons.

Properly maintained pool water has no chlorine odours or tastes and does not cause bather’s eyes to burn or skin rashes.

While the modern North American scientific community is finally doing its own research, replicating the European studies in actual swimming pools, they are still several decades behind their European counterparts.

Winds of change

During my 47 years of visiting public pools across Canada, I cannot think of one facility that would pass the DIN requirements; thankfully, that is starting to change, as there are several pools presently being built to DIN standards in Canada.

Conclusion

In North America, billions of gallons of unheated, out-of-balance, expensive taxpayer-treated water is wasted every year. Ever-rising chlorine levels, designed to solve numerous resulting mechanical and circulation problems, have proven costly and potentially hazardous to the users, staff and building lifecycles. With these factors in mind, perhaps it is time for the Canadian aquatic facilities industry to look into these European standards for inspiration. Adopting DIN standards could be one of the most important and impactful steps the North American pool and spa industry could make.

 

Dennis Ashworth joined the aquatics industry in 1963. An author, lecturer, industry court expert witness, builder and designer, he operates SP&S Swimming Pool & Spa Equipment, a water treatment business based in Newmarket, Ont. He can be reached via e-mail at swimpool@msn.com[4].

Source URL: https://www.poolspamarketing.com/trade/understanding-din-standards/

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