Managing the water supply correctly is just as important to laundry’s overall operation and cost effectiveness as purchasing the right wash chemistry. There is no point in buying expensive chemicals if they are then dosed into water which is not suitable for washing textiles.
At best it is pouring money down the drain (hard water neutralises even the most expensive detergents) and at worst it could create an infection outbreak.
Many launderers regard water as a commodity that is virtually taken for granted and purchased as part of the day-to-day operation of the laundry. Regardless of how much is paid for the water supply or the effluent charges associated with disposing of it, failure to adequately manage water supply and its use can have far-reaching effects.
From the moment the water passes through the meter and enters the laundry premises, it needs to be carefully managed and controlled in much the same way as a business manages the fuel used in its delivery vehicles.
Water is the fuel used to operate both the laundry boiler and washing machinery. Failure to control its quality is as damaging as filling a diesel-engined car with unleaded petrol.
The first part of water management is to ensure that the water is in the right condition to be used. Failure to do this risks premature fabric damage. If there is any contamination in the water when it is received, then it will affect the quality of the finished work. For example, if work is being carried out on the water mains one mile away, then the supply could well be brown with mud and rust particles in it, in addition to the hardness salts and other possible contaminants commonly found in our water supply.
Other more unpleasant contamination can be found in borehole water, especially if the water catchment source is in a rural area and there is a lot of livestock in the pastures. Possible urine and faecal contamination means that the water needs to be filtered, softened and possibly disinfected before it gets anywhere near to being used in the laundry.
Most modern water softeners will have fine mesh or membrane filters at the water entry point and many newer units will also be fitted with automatic sensors to detect when the resin in the water softener needs to be regenerated. Operators need to ensure there is a plentiful supply of brine available. For laundries that don’t have a modern water softener with an intelligent controller, water hardness should be routinely checked at least twice daily to avoid contaminating the whole system with hard water.
Resins used in water softeners have a limited ability to remove the hardness salts in the incoming water supply. Therefore, if the water hardness varies, even when using the same volumes of water each day, the periods between the softener regeneration can vary.
Say, for example, a laundry is processing 15tonnes of laundry per day in washer-extractors with an average water consumption of 20litres/kilogram and the raw water hardness is 15degrees Clarke* (214.5ppm or 12.5grains/gallon calcium carbonate equivalent) and regenerating once every 8hours at the end of the normal working day.
This means the laundry must remove 15,000kg x 20litres x 12.5grains = 3.75million grains of water hardness per 8hour day.
If water hardness increased by just 3degrees Clarke, the laundry needs to remove 4.52million grains of hardness and regenerate 100minutes BEFORE the end of the working day, otherwise most of the detergent dosing throughout this period will be neutralised by excess hardness.
Remember to routinely check both the water pressure drop across the softener and the cleanliness of the filter screens at the water inlet. If the resin is not back-washed correctly with a high enough water pressure or for long enough it can quickly clog and block, forming channels through the resin bed that not only reduce the water softening capacity of the plant but can lead to reduced water supply – with potentially disastrous results.
The same applies with the water inlet filters. These can also become blocked and reduce water flow or they can become corroded and start to release rust into the water, which will affect the condition of the resin in the softener and also affect the quality of the finished work by turning it yellow. The effects can be even worse where sodium hypochlorite bleach is used. The iron in the rust catalyses (accelerates) bleach damage to cotton, so that textiles go into holes very readily.
The next part of water management is water storage capacity. Unless a laundry is fortunate enough to have two water softeners so that whilst one is producing soft clear water the other is regenerating, then it is essential it has a soft water storage tank. This tank, especially in older laundries, will probably be located on the roof of the building and be of sufficient capacity to meet the production requirements for at least 4 – 6hrs.
Having the tank on the roof ensures that there is a constant head of water to produce good water pressure into the washing machinery without any production delays caused by fluctuations in mains water pressure.
It also means that if the washing machinery has been piped up well, there should be very little variation in water pressure when two or more washing machines call for water at the same time.
If this is not the case, then the diameter of the header pipe and individual off-takes should be examined and increased where necessary. There are pipe sizing charts generally available, based on a loss of head of only 1cm of water per metre run. The size of the off-take pipes should match the inlet size of the washer extractor itself.
If the guidelines are followed, then two large washer-extractors will make a rinse dip simultaneously in less than one minute. Before purchasing additional washer-extractor capacity, it is worth looking at raising water delivery speeds (pumping the supply if necessary) because this can raise laundry output at a fraction of the cost of an extra machine.
Most modern washing machinery will be automatically controlled and the timer on the process unit does not start operating until all the desired wash process parameters have been achieved – the correct wash dip has been delivered and the correct wash temperature achieved. If the water supply is poorly connected, the first washing machine in the line will have the highest water pressure and the supply will reduce dramatically for those washing machines furthest from the water supply inlet.
This means that a standard wash process of, say, 35minutes duration can take in excess of 65minutes, because of the delays whilst waiting for the water supply.
Adequate capacity
Regardless of the number of water softeners, a water supply header tank is always advisable. The tank should be of adequate capacity to match the production requirements of the laundry. If the laundry is based on a tunnel washer and washer-extractors, then it is essential to pipe the tunnel so that it always has preference for water pressure. For example, a tunnel on a 2minute cycle cannot afford to wait for water pressure to be restored and an intermittent loss of pressure may result in a blockage.
Even where a water storage header tank is installed correctly, it must be maintained properly. It should be completely sealed to prevent atmospheric dust and dirt settling into the tank and to prevent birds and other wildlife from gaining access to the inside of the tank. On many occasions the water supply to the laundry has been heavily contaminated with coliforms and other potentially harmful bacteria because a bird or a rat has managed to get inside, been unable to get out again and drowned. The body then gradually decomposes to provide a source of potentially lethal contaminated water to the laundry. There is little point in incurring the costs of thermal disinfection during the wash process if you are then going to rinse the clean work in water contaminated by rotting carcasses.
The build-up of sediment in the base of the water header tank should be checked at least once every six months. Most tanks need regular draining and internal cleaning to get rid of silt.
Even more important is the build-up of very fine colloidal rust particles, because of the effect these have on colour (and speckles) and textile life.
Even with effective water filtration and a secure tank, a certain amount of dust and dirt will accumulate and settle in the tank.
If the tank is permitted to run low at any time – especially if the water inlet is located close to the bottom of the tank – sludge and slurry will be agitated and cause the water to turn dark brown. A good way to check this is to fill a machine with water first thing on Monday morning and then shine a torch through the front glass into the machine through the water whilst the drum is stationary. The back plate of the inner basket should be clearly seen if the water is clear. The best machine to choose is a medium-sized, glass fronted washer-extractor.
Management of water is just as important as the management of the fuel in a car. Failure to use the right fuel or make regular maintenance checks can result in being stranded on the highway. The same thing will also happen if a laundry doesn’t manage its water – except the business will be on the highway to financial disaster.
*To convert degrees Clarke to ppm multiply by 100 then divide by 7.
