RAI Info

Water Softener Facts and Fiction

Commercial dish wash and laundry must be supplied with a softened water supply to work correctly. You can soften water with chemicals but it’s a lot more expensive than putting salt in a softener. Zeolite-based water softeners – whether stand-alone or integrated – need a supply of salt so they can periodically recharge the ion exchange column. Salt does not soften water. Salt recharges the ion exchange column in the softener – it is the zeolite ion exchange unit that softens the water.

[notice]You need to ensure the water softener is ¾ full of salt at all times.[/notice]

Here’s why…

[important]How Water Softeners Work[/important]

Most water softeners use an ‘ion exchange’ resin in which hardness ions are exchanged for sodium (Na+) ions. This works because by and large sodium salts are soluble and magnesium and calcium salts aren’t. So, any magnesium or calcium salts that pass through the resin have their calcium or magnesium swapped for sodium. Think of the resin as being a magnet and the hardness being iron filings. From time to time the resin needs ‘recharging’ by flushing a large amount of common salt (sodium chloride – NaCl) through to replace the sodium and wash out the other salts it has taken out of the water. A bit like getting the iron filings off the magnet.

Once the resin is saturated with calcium and magnesium the softener enters a 3-phase regenerating cycle.

  • First, the backwash phase reverses water flow to flush dirt out of the tank. In the recharge phase, the concentrated sodium-rich salt solution is carried from the brine tank through the mineral tank. The sodium collects on the beads, replacing the calcium and magnesium, which go down the drain.
  • Once this phase is over, the mineral tank is flushed of excess brine and the brine tank is refilled. Most water softeners have an automatic regenerating system. The most basic type has an electric timer that flushes and recharges the system on a regular schedule.
  • During recharging, soft water is not available.

A second type of control uses a computer that watches how much water is used. When enough water has passed through the mineral tank to have depleted the beads of sodium, the computer triggers regeneration. These softeners often have reserve resin capacity so that some soft water will be available during recharging.

A third type of control uses a mechanical water meter to measure water usage and initiate recharging. The advantage of this system is that no electrical components are required and the mineral tank is only recharged when necessary. When it is equipped with two mineral tanks, softened water is always available, even when the unit is recharging.

This is the reason you need to keep plenty of salt in the tank: you never know when the unit will take itself offline to recharge the column.

[important]Types of Water Softener[/important]

Water softeners for commercial dishwasher come in 5 varieties: manual, integral, continuous, automatic cold and automatic hot.

Manual Water Softener

A stainless steel cylinder about the size of a medium fire extinguisher with a water inlet and water outlet. Manual water softeners need to be manually regenerated several times a week depending on water hardness and number of washes. This is a massive pain in the arse and rarely gets done. Manual water softeners are fitted near to the dishwasher or in a cupboard nearby and regular access to them is needed.

Integral / Internal Water Softener

These look similar to the water softeners in domestic dishwashers and need to be topped up with salt regularly but unlike domestic dishwashers, they do not operate automatically. On most machines the customer has to remember to operate the water softener by running a recharge cycle. On a higher specification machines a warning light will come on reminding you that a recharge cycle is needed.

Continuous Water Softener

These look and operate just like the water softeners in domestic dishwashers; all you have to do is keep them topped up with salt.

Automatic Water Softeners (Hot / Cold)

The water softener is plugged into the mains and connects to the water and drainage supply. Its operation is fully automatic; it just needs to be kept full of salt. Automatic water softeners are usually installed next to the dishwasher, under the dishwasher stand or in an adjacent cupboard.

Choice of Softener

The manual water softener is the cheapest and will work in all water conditions. On the downside it takes the most looking after and a regular routine to maintain its performance. People often forget this with the inevitable impact on wash results – which they blame on the chemical. Integral water softeners have very limited resin capacity and so are only suitable for moderately hard water areas and for low usage situations. Continuous water softeners have the same low resin volume but as they operate continuously, they are suitable for moderate use in moderate water quality areas. Automatic water softeners have the resin capacity and are capable of operating in all water quality areas and at high wash volumes but are the most expensive.

Although you can get chemicals formulated for hard water areas there really is no substitute for a water softener when one is needed. Also salt is cheaper than chemicals; spending a few hundred quid on a softener soon pays for itself.

[error]Magnetic Water Softeners[/error]

Many claim you can soften water with a magnet. You can’t. It’s everso simple; water isn’t magnetic, nor is hardness. (A related scam is that you can clean beer lines with magnets – this is also nonsense).

Magnetic water softeners are claimed to rely on several principles depending on the particular system in question and how gullible the sales person thinks you are. Claims include water has a dipole and so can be softened using magnetism. This is Utter, Utter Bollocks (µ2B). Water does have a dipole has an electrical dipole, not a magnetic one and nothing will change that. No amount of magnetism will soften water.

Another explanation quoted is that magnetic water softeners ‘ionise’ water to remove hardness. Rubbish. You can’t ionise water with a magnet – or anything else – except by chucking ions into it. (Atoms in many compounds are held together electrostatically; when you chuck crystals of table salt (sodium chloride) into water it dissociates into ions of sodium and chloride Na+ and Cl).

Another is ‘magnets decrease surface tension’. Again, total rubbish. You cannot soften water with magnets no matter how much slick science-y sounding stuff you put in a brochure. It’s pure nonsense.

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