Water Treatment Advice

Hardness and impurities in the mains water supply will result in lower dishwashing standards and higher detergent, energy and equipment servicing costs. That's why Meiko, a world leading specialist in commercial dishwashing systems, takes a close interest in water treatment technology and can provide in-depth advice and a complete programme of water treatment appliances to suit most conditions.

Dealing with hard water

The majority of caterers are in area where the water supply is classified as moderately or extremely hard. This happens because the water contains dissolved chalk, limestone and other minerals. Changes in water industry sourcing policies have made matters worse in some areas, adding hard water to supplies which traditionally were soft.

Water hardness is typically expressed in Britain in either degrees Clarke or parts-per-million (PPM) of dissolved solids. Water rated above 7 degrees Clarke or 100 PPM will cause scale formation on all surfaces which come into contact with it; i.e. pipes, tanks and heater elements. This scummy furring-up reduces the efficiency of the equipment and makes it more prone to breakdown. At the same time, scaled up elements use up more energy; (scale just 1.6mm thick causes a 12% loss in heating efficiency). Chemical costs can also be higher because a greater concentration of detergent is needed.

Water Softeners

Meiko offers a complete range of water softeners which work on the ion exchange principle (sometimes also referred to as cation exchange or base softening). Units work by passing water through resins in the form of millions of tiny beads held in a plastic drum. Passage of water through the resin brings about a chemical change where the calcium and magnesium ions in the water lose their positive charge and are exchanged for non-hardening sodium ions.

The resins should never need replacing but require regular regeneration. This entails flushing a small amount of brine through the cylinder and is normally carried out when the dishwasher is not in use. Regeneration refreshes the resin while the hardness salts which have accumulated in the resin pass harmlessly to drain rather than clinging to surfaces inside the machine.

Duplex Water Softeners

Duplex softeners which automatically regenerate themselves relative to the flow of water are available for any dishwashing requirement. These comprise two cylinders one of which regenerates while the other continues in use, ensuring a continuous supply of softened water irrespective of water quantities used.

Water Demineralisation

In applications where the quality of the finished ware is especially critical, such as high quality glassware or cutlery, water demineralisation units not only soften hard water but also, thanks to selective dealkalisation resins remove traces of heavy metals such as lead, copper, mercury, etc.

Further 'polishing' of the water is aided by a carbon filter, which removes any traces of organic matter and chlorine. The resultant water is chemically pure and leaves no visible residues when it evaporates, which means the glassware and cutlery can be washed to exceptionally high standards with no need for hand finishing. Resins are held in cartridges which need to be changed at predetermined intervals.

What is Osmosis ?

Osmosis is the natural process by which plants and trees take up nutrients from the soil around their root systems. When solutions, of different concentrations, are separated by a semi-permeable membrane - a membrane which will only allow the passage of water and not the dissolved species - water will naturally pass from the dilute solution to the more concentrated, in order to make the solution strengths equal. This phenomenon is called osmosis.

Reverse Osmosis

In applications where a high quality finish is required on glassware and cutlery, without the need to hand polish, we recommend the installation of an Osmatron Reverse Osmosis system.

Reverse osmosis works by passing water via a high pressure pump through a semi-permeable membrane which allows the passage of water but not the dissolved solids in the water, which are concentrated and directed to the drain. Up to 97% of minerals in the water are separated off. Treated water is stored in the unit and automatically delivered to the glasswashing machine via an electronically controlled stainless steel pump. To ensure optimum membrane life, water should be softened e.g. in a central water softening system.

Water Connection Equipment

UK water industry bye-laws stipulate that contaminated water in the machine (for example, alcohol from dirty glasses, or detergent) cannot under any circumstances siphon back into the mains water supply.

This is not a problem on machines which are solely connected to an external hot water supply but can be on machines which receive their water from the cold water mains. The answer preferred by the UK water industry is an air-break in the water connection, known as a type A air gap. Should water flow back, it cannot bridge the gap.

The size of the gap, which can be integral with the machine or in a separate break-tank, depends on the gauge of the pipe. Units may also house a booster pump if it is necessary to deal with loss of pressure on the incoming water.

Meiko offers complete solutions for connecting machines correctly, the type 'A' air gaps manufactured by Meiko have been tested and are approved by the WRc (Water Research Centre). The WRc issues approval listings called IRN, or Installation Requirement Notes, and failure to comply could leave the caterer open to prosecution. The lowest IRN numbers (IRN 000 and 001 indicate that a machine can be connected to any water supply without needing any extra fitments.

Matching softeners to needs

Integral water softeners can be incorporated in Meiko frontloading and hood-type dishwashers and suit operation with an incoming hot water supply up to 55°C. Salt for regeneration is located in a 0.8kg capacity container accessed via the floor of the wash tank, regeneration takes approximately 25 minutes. Following regeneration, the fill and final rinse valves are opened to enable the base exchanger and rinse boiler to be flushed out at full pressure, thus removing any salt deposits and preventing the formation of chloride which could otherwise corrode the stainless steel.

Stand alone water softeners are compactly sized for unobtrusive siting near the feed-in point into the machine. Units contain sufficient resin to enable heavily used dishwashers to run for many days before needing regeneration, which is carried out automatically at time intervals pre-set on a simple time clock. A manual over-ride button permits variation of the pre-set times, if required.

The choice of softener depends on how much water is consumed each day. This is determined by multiplying the machine's rinse consumption per cycle by the number of racks handled per day, plus the wash tank volume. Meiko offers a choice of six automatic softeners able to deal with cold water in volumes from 665 litres up to 4600 litres before needing regeneration.

There are also three warm water feed models to deal with circumstances where unsoftened water is used in pre-heated form up to 65°C. Booster pumps can also be supplied if the water pressure is too low.

There is also a choice of hot or cold water softeners with integral electronic controlled pump set specifically to deal with low water pressure applications.

For further details and pricing on Meiko water treatment systems see below, or contact our sales team on 01476 591650.