SPECIAL REPORT: Water Filtration For Cooking And Refrigeration

If someone asked you for a short list of hot topics in foodservice these days, water quality and filtration would have to be near the top. Seems as if we just can’t get enough on the subjects. And small wonder: Water is crucial in foodservice, quality has always been spotty and prices keep going up. Combine all of that with equipment maintenance and replacement costs, and you’ve got yourself a touchy subject.

Mike Sherer covered the topic extensively in “Water Rights,” his cover story for the February 2011 issue of FER (which you can reference at http://bit.ly/SdBKaZ). Then we followed up with two sessions at FER’s Multiunit Foodservice Equipment Symposium (MUFES) in January at the Barton Creek Resort in Austin, Texas. Those sessions delved even more deeply into explaining chemistry and technical details.

Total Dissolved Solids

The water that arrives at your restaurant includes a lot of things besides good old H20, as Brian Madden noted at his MUFES session on filtration for cooking equipment. Water quality can vary greatly from town to town and sometimes from neighborhood to neighborhood, says Madden, who spent nearly 20 years focused on water quality and filtration before assuming his current role as v.p. of sales at Sandstone Group.

Geography and type of water source both make a difference, he notes. Is your water coming from a lake or river? Is it coming from an aquifer? Groundwater tends to have a lot more materials in it. How does the municipality treat the water? Even the condition of the pipes on your property and nearby can make your water different from other water in the same jurisdiction. What’s in your water has big implications for your equipment and for what filtration, if any, you’ll want to use.

Your water can have suspended, undissolved solids in it, such as wood and dirt particles. And it can have a variety of dissolved solids. The term Total Dissolved Solids, or TDS, is used to refer to all of the positive- and negative-charged ions in the water, including a hodgepodge of minerals, salts and metals that can have many affects you don’t want.

In the bigger picture, the minerals, salts and metals can skew the power of hydrogen, more commonly known as pH. The pH scale, as many of you will recall from your chem classes, is a 14-point scale. A pH of 7.0, right in the middle, is considered neutral, neither acidic nor alkaline, and that’s what pure water is. The lower the number, the more acidic; the higher, the more alkaline. This information helps you read water-test results. The pH has implications for taste and corrosiveness, among other things. Acids corrode metals; alkalinity tends to coincide with hardness, which inhibits the effectiveness of soaps.

“Larger water companies usually have their water-quality reports online,” Madden told MUFES attendees. “Look for the pH level: It’ll be above 7.0 to keep it from causing corrosion.”

A subset of TDS, “hardness” refers mainly to compounds of calcium and magnesium in the water Madden says. They’re not health issues, and in fact have some nutrient value. But hardness can impact taste and, more important for our purposes, can add to scale buildup in cooking equipment and refrigeration systems, such as icemakers. Measure hardness with a number. Most of the time it’s milliliter per liter or ppm. One grain per gallon usually is equal to 17 ppm. About half of the U.S. water supply is rated hard or very hard. In many locations, a water softener is necessary.

Although softeners are a topic unto themselves, it’s worth noting that they’re ion-exchange systems that generally use two tanks. One tank holds salt water, and the other is full of resin beads saturated in sodium. Incoming water pumps through the beads, which give up sodium as they exchange it for the calcium and magnesium, capturing the minerals until the sodium level drops to where it’s no longer effective. Then, in a regeneration process, the salt water in the second tank is backflushed through the bead tank to both flush out the minerals and restore sodium levels and the beads’ capture capacity.

Chlorine & Chloramines

Another big category of TDS, Madden notes, includes the disinfectant chemicals that water companies add to the water for public-health reasons. Historically, the favorite has been chlorine, and it has been used widely for more than a century. But in more recent decades, an increasing number of jurisdictions have been reducing chlorine levels and supplementing with added chloramines, which are a combination of chlorine and ammonias. Chloramines are not as strong as straight chlorine, but they’re more stabile and last longer in the water system, meaning they offer some residual disinfectant after chlorine has dissipated. Also, chloramines are friendlier or milder than chlorine, an important quality for certain environmental and health priorities.

Why Filter?

So, after that big preamble about what’s in the water, why do these solids become a concern for cooking equipment? The bullet points: The minerals and salts (corrosive chlorides) build up in the form of sediment in cooking equipment that requires hot water for heat transfer—especially equipment that generates steam. As mentioned in a recent article on steamer and combi maintenance [FER December 2012, page 63], the deposits tend to be more pronounced on the hottest surfaces. The buildup acts as an insulator, not only slowing the heat-transfer process, but also causing excess energy consumption and excess heat that can prematurely destroy the heat source and nearby components. Additionally, sediments over time can physically clog inlet and drain lines as well as anywhere openings are small to start with.

In the case of chlorine and chloramines, the real problem—and it’s a huge one—is metal corrosion. Both chemicals are extremely corrosive to iron, steel and copper, just to name the biggies, and they’re even more destructive when heat is involved.

So, to protect your equipment investment from premature failure and huge, avoidable service bills, in most parts of the U.S. you really need to filter the water. The question then becomes, “Which types of filters should be used for what local conditions?”

Types Of Filters

You can start the decision-making process by getting a water-quality report from your local water company. If you want to delve more deeply and see whether your own neighborhood conditions are different from the water company’s system averages, you can have water from your site tested or you can get a kit and test it yourself.

After you have the data in hand, your filtration supplier can sort through your options. You may want to filter all of your incoming water, or you may want a specific filter for a specific piece of equipment, depending on your local conditions. Types of filters are covered in detail in the previously mentioned FER February 2011 cover story, but let’s quickly review the options:

• Mechanical: Removes large sediment, such as twigs and rocks.

• Carbon: Actually a type of mechanical filter, carbon filters come in brick and granular designs. Impurities become attached to the carbon’s surface. As the most effective way to eliminate chlorine and chloramines, carbon filters are finer than coarser mechanical filters. Generally, multi-stage filtration should progress from coarse to fine.

• Membrane separation: Reverse-osmosis filtration is the best-known type of membrane treatment, which is finer than carbon filtration. Water is forced through a membrane, usually a very fine one, that catches virtually all TDS and chemical contaminants; what passes through is pure water. Particles down to 0.1 microns typically are caught; some ultrafine systems can intercept particles as small as 0.01 microns.

• Scale inhibitor: Inhibitor materials—polyphosphates are the most common—bind with minerals or cause them to crystallize, making them unable to precipitate and cling to surfaces in the equipment.

On The Refrigeration Side

Refrigeration has its own considerations, as MUFES attendees heard from Scott Hester, v.p. of Refrigerated Specialist Inc. and immediate past president of the Commercial Food Equipment Service Association.

Although his session more broadly focused on ice-machine maintenance, including filtration, Hester notes many of the same water contaminants need to be dealt with, but for different reasons and sometimes with different results.

Scale is the biggest concern wherever water is flowing in the machine, he said. Refrigeration-related scale can be controlled by the same types of filters used in cooking applications as well as with regularly scheduled cleaning.

Slime is another major concern, mainly where water either is not moving or is slow. Although filtration can’t prevent slime because it’s caused by airborne yeasts, molds and algae, filtration can and does complicate the problem.

“After the water filter has removed the chlorine,” Hester laughs, “we get the opportunity to grow some green stuff.” To combat algae, which need light to grow, use opaque water and beverage lines. For other bioforms, he points out the industry now widely uses antimicrobial sachets, ozone treatments and other methods to introduce sanitizing agents into the machine’s airspace.


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