A History of Dishwasher
A dishwasher is an appliance/person used for washing plates, dishes, forks, spoons and other utensils. A dishwasher generally refers to two things, a person washing pots and pans by hand, or a mechanical appliance which does part or all of the washing by itself.
The modern day mechanical appliance runs on electricity, and apart from needing to be loaded, does all the washing by itself. The use of mechanical dishwashers in developed countries is widespread, with the vast majority of residential homes and commercial eateries using them.
Mechanical dishwashing machines were invented much earlier than their electrical counterparts. Reports suggest the first patent for a mechanical dishwasher was issued around one hundred and sixty years ago. But the current dishwasher owes it’s genesis to an invention of Josephine Cochrane.
Her hand operated dishwasher was unveiled in 1886 at the World’s Fair, which happened to be hosted in the USA, in the city of Chicago. Josephine was a wealthy lady with plenty of servants, and it’s claimed that her motive for inventing her machine was to stop her servants damaging her fine china.
The first dishwasher which incorporated plumbing was developed in the roaring twenties. Invented by W H Livens, it was a front loading machine, commercially a success and continued to evolve until electrical components and elements were installed. The 1970’s was the decade when dishwasher became a common appliance in most western households.
The modern day dishwasher works with a simple to complex timing mechanism, which can be operated through either mechanical or electronic buttons. A dishwasher takes water from the home’s water supply through an intake valve. A pump connected to an electric motor then forces the water to a spray arm. The spray arm is located at the top of the internal basin, and sprays water and detergent onto the plates etc.
Capacity of Dishwashers
The capacity of a dishwasher corresponds to the amount of plates and utensils which can be placed within it per wash cycle. The exact terminology used by the industry is ‘place settings’.
And it’s an international standard followed by most countries. One ‘place setting’ refers to the number of items that can be used in one meal by one person.
One place setting:
- One plate.
- One soup bowl
- One desert bowl.
- One tea cup.
- One tea cup saucer.
- One fork.
- One Knife.
- One desert spoon.
- One tea cup spoon.
The size of the above items is not specified in the ‘place settings’ standard. Only that, one of the above, of an average size, can be held by the dishwasher.
Therefore, the ‘place settings’ standard is not an exact science, but a general guideline. Dishwashers typically have between four and fourteen place settings.
The average is around eight, but it’s recommended (space permitting) to have in the region of twelve place settings for your new dishwasher.
Size of Dishwashers: Compact, Slimline, Fullsize
The capacity of a dishwasher is largely dependent on it’s overall size / dimension.
As most modern dishwashers are usually installed under worktops or within cabinets, manufacturers stick to standard dimensions.
The three standard width sizes are as follows,
1. Compact – Width 55cm wide. Usually placed on a worktop.
2. Slimline – Width 45cm wide. For small families, singles and couples.
3. Fullsize – Width 60cm wide. For large families and businesses.
Of the three above form sizes, the fullsize dishwasher is the one most people will think of as ‘the’ standard size. Measured as sixty centimetres in Europe and twenty four inches in North America.
The width and depth is the same for fullsize dishwahers. But it does differ for compact and slimline dishwashers. So for example.
1. Compact – Depth is 50cm
2. Slimline – Depth is 60cm
3. Fullsize – Depth is 60cm
The final dimension we need to consider is the height of the three form factors.
1. Compact – Height 45cm
2. Slimline – Height 85cm
3. Fullsize – Height 85cm
Performance of Dishwashers: Cleaning, Drying, Energy
When it comes to performance, dishwashers are graded on three important performance criteria. The grading system goes from A down to G. With grade A being the best. The three performance categories are as follows,
- Cleaning performance. Indicates how well the machine can remove dirt and grease.
- Drying performance. Measures the amount of excess water at the end of a wash cycle.
- Energy efficiency. A high performer can save a substantial amount of water and electricity.
The cleaning performance of a dishwasher is not only a visible indicator. There is also hygiene to consider. Manufacturers claim that dishwashers kill more germs than washing at a kitchen sink.
A dishwasher will operate at temperatures of around seventy celcius. Which is higher than hand washing. This means that dishwashers wash close to or exactly at sterile levels.
A dishwasher can also save time. Research has shown that a dishwasher can save a couple of days in saved time, in comparison to washing dishes by hand, over a year long period
The green credentials of dishwashers are clear cut. An average wash cycle at a kitchen sink (for a family) uses around fifty litres of water. Whereas a full dishwasher wash cycle uses around twenty five litres of water on average. This can add up to a considerable amount of water per year.
Sound damping is a final performance consideration. Manufacturers have done a good job of developing superior sound absorbing machines. You should expect a decibel level of around 42. Older machines are around 55-70 decibels. A difference in 10 decibels, which is three to five times quieter.
Features of Dishwashers
When it comes to features, wash programmes are a primary consideration. The more the better. Some of the key programmes are as follows,
1. Fast cycle, plates with little dirt on them.
2. Economic, low temp, saves on electricity.
3. Performance, high temp, intensive wash for caked on dishes.
4. Half load, for fewer dishes, less litres of water are used.
5.Glass wash, calmer water pressure to protect delicate and expensive glass.
Hardware features are few and far between. An LCD display is standard on virtually all dishwashers. And a clear and easily understood panel is desirable. Apart from this, internal adjustable racks and baskets are another option to look for.
When it comes to cosmetics, dishwashers are usually rather bland in design and coloured in white, gray or silver. For the style conscious, built in dishwashers are either hidden behind a kitchen cabinet, or the door of the dishwasher is attached with a cabinet facade. However, it has to be said, Smeg have recently produced a range of 1950’s styled dishwashers in a selection of extravagant colours.
Sound dampening has recently improved for high end dishwashers. While an entry level machine will produce a decibel level of around seventy, a high end machine will only produce a decibel level of forty. Which is similar to the sound a kettle makes.
The internal basin of dishwashers is either made from plastic of stainless steal. Stainless steal basins last longer and are to be found in all high end machines. A filter is installed in most basins, which will need to be cleaned manually on low level machines, but, automatically cleaning filters are available. A basin will typically include two draws for inserting plates, utensils and cups. The more you pay for a dishwasher, the more likely the draw can be collapsed, removed, and folded, to increase greater flexibility.
On expensive dishwashers, features such as a delayed start time are included. Microprocessors and sensors have enabled dishwashers to alter the length of wash cycles by sensoring water temperatures. This is useful for people who do not wash on full loads, due to the resources saved.
For medium level machines, an LCD display to operate the wash programmes and to show the status of the current wash cycle comes as a standard. The dishwasher door should also self balance when attempting to load and unload pots and pans. A cutlery basket and adjustable internal baskets are to be found in virtually all dishwashers.
So to conclude, an LCD display, a self balancing door, baskets and plenty of wash programmes are about the pinnacle of features to be found on an average dishwasher.
Installing a new dishwasher
When purchasing a new dishwasher the process of installing it is usually included free in the price, or for an additional fee. If the installation is an add-on fee and you are considering saving yourself a little money, then this page will highlight a simple guideline for installing a dishwasher.
First things first, installing a dishwasher is not child’s play, and for the novice budding engineer, it is as complicated as some retailers would lead you to believe. But, once you do understand the in and outs of how’s a dishwasher is installed, repairs to simple malfunctions may also be a possibility.
The process for installation is highlighted below. However, it may not apply to all homes, and it is far from being comprehensive enough to help those with zero diy experience.
First the electricity for your home needs to be switched off. You will need to locate your circuit breaker box to achieve this.
The next thing that needs to be achieved is to switch off the water supply to your home. The primary water supply is normally routed through the kitchen. A valve to shut off your water supply should be located under the sink in your kitchen. Once you believe you have achieved this, then try turning your taps on and off around your home.
The above two steps will make sense now. You will now need to connect the water supply and electricity to the dishwasher. A corner piece with a 90 degree ‘T’ angle is needed for the water supply. This part may not have been included with your dishwasher. One end of the corner piece is installed into the dishwasher and the other to the household water pipe. A dishwasher should only need a cold water supply.
Now, if your dishwasher has a plug attached, then the process of connecting electricity to your dishwasher has been simplified greatly. If not, then you will need to double check you have definitely switched off the electricity supply to your home. Then you will need to connect a electrical wire to the junction box on your dishwasher. If there is no wire behind your dishwasher, then you will need to run a cable from your breaker box to the position behind your dishwasher.
Finally you will need to connect drainage for the waste water. How you proceed with this part will depend on the configuration of your home. But it should come down to one of two things. Connecting a waste hose from your dishwasher to the standpipe of the sink in the kitchen. But if the dishwasher is too far from the kitchen sink, then a waste pipe will need to be fitted on the wall behind the machine, your waste pipe will be connect to this outlet instead.
So to sum up: First turn off the water and electricity supply to your home. Then connect the water and electricity supply to your dishwasher. Then install a drainage hose. After that you simple need to push the dishwasher back into place.
The manual with your dishwasher should include any intricacies your machine may have in it’s installation. And likewise the above guide is only a rough outline for an atypical home. This guide may not apply to your home. If you are in any way uncertain, then either research the above steps in-depth from other online sources or simple pay for the installation from a professional.
Tips: How Best to Use a Dishwasher
Below is a list of things to do and avoid when operating a dishwasher.
1. Do not wash crystal, gold plated china, pans made from cast iron, silver plated china, copper, kitchen utensils without a steel handle such as wood or plastic. Any of these products may be faded or break from continual dishwasher washes.
2. When unloading a dishwasher it is advisable to unload the bottom draw first. Most dishwashers do not dry out all of the water. So, when cups are removed from the top draw first, they may drop water onto the bottom plates and utensils.
3. Some dishwashers contain a filter which needs maintenance. You should periodically check to clear any residual waste or limescale from the filter.
4. Some dishwashers require salt and rinse aid alongside the detergent to perform at their maximum. The salt helps to soften the water and the rinse aid contains surfactants to stop droplets of water forming and smearing glassware and plates. Dishwasher salt is not the same as culinary salt, and is purged of impurities, manganese and iron. Inserting salt which is not designed for a dishwasher will more than likely damage the softening system.
5. Over or under filling a dishwasher has it’s disadvantages. When too many items are placed inside, then the dishwasher will have difficulty cleaning to it’s peak performance. Cups and plates may also knock against each other and become chipped. While under filling a dishwasher does not have any disadvantage to the cleaning performance, there will be a waste of detergent, water and electricity.
6. Check that the dishwasher sprayer and sprayer arm have a free motion to clean the whole of the load.
Soft and Hard Water: It’s Implications for a Dishwasher
So you may be asking yourself what is soft and hard water, and how does this effect me and my dishwasher? Well, hard water is rich is minerals, primarily two minerals,
1. Calcium Ca2+
2. Magnesium Mg2+
To a lesser extent some hard water locations may have a small to medium amount of Aluminium, Iron and Manganese.
Now, these minerals have their advantages for practices such as brewing beer. But, when it comes to the internal parts of a dishwasher they prove problematic. The minerals attach themselves to heating elements within the dishwasher, which is known as scaling or limescale. Over time this will negatively effect the performance of a dishwasher and may destroy some elements.
Most dishwashers have a solution to this problem. They have a salt dispenser, which adds a small amount of salt to the water, which in turn helps to soften the water and lowers the risk of scaling.
A survery of England and Wales has concluded that the majority of England is a hard water location. Wales on the other hand is mostly a soft to medium location. There are some exceptions in England, such as the North West and North East and Cornwall, which is soft to medium. But, virtually the whole of the Midlands and South of England is hard water.
Detergent is split between two categories, with two options within each. Fist the form it comes in,
1. Tablet form
2. Powder form
Then there is the chemical composition of the detergent, which, due to environmental concerns within the wider society, is split between two camps,
Obviously the first category is self explanatory, but the second category is less clear. What separates biodegradable and non-biodegradable detergent is most usually phosphates. Phosphates are used by detergents to combat hard water. Hard water can be found in most midland and southern areas of England.
Hard water contains Magnesium and Calcium ions which produce scaling. Phosphates aim to soften the water by lowering the mineral content of it. But, the problem with phosphates is they do not naturally biodegrade and therefore are a problem for the environment.
The actual cleaning composites of the detergents is a mix of either chlorine or oxygen bleaching agents, enzymes, starch, anti cake and foam agents and gels. These composites help to break down the food deposits and then to bleach them.