From DIYWiki
Revision as of 11:28, 12 September 2012 by NT (talk | contribs) (→‎See also: m)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to navigation Jump to search

This applies to domestic dishwashers. Catering dishwashers are quite different.


  • A £300 machine lasting just 10yrs = £30/yr = 57p a week.
  • Electricity use is comparable to power use for handwash water heating, so is not an added cost
  • Detergent tabs 7.5p a wash
  • salt £1.30/yr = 2.5p/week

2 machine washes a week = 57+15+2.5 = 84.5p

If we estimate 12 minutes a day handwashing, that's 84 mins a week.

Thus each hour of handwashing avoided costs 60p. Working for 60p an hour seems to be popular.

Water use is typically less than hand washing dishes.

The wash program

The wash cycle consists of 4 parts:

  1. prerinse - softens dried foods, usually cold
  2. main wash
  3. rinse
  4. dry - old machines hot dry, new machines use a slow cold dry

The biggest difference between different wash programs is the water temperature.


Baked on grease can be removed from wire oven shelves by dishwashing, which softens it temporarily, then wiping with a copper scourer. Remove from dishwasher at the end of the wash cycle while its still hot, not after the final cold dry is finished.

Baked on grease is mostly not removed from non-stick oven trays, but regular washing slows its formation.

Egg and egg mixes can cook and stick on rather than clean off with some wash programs. Egg needs to be cold washed to avoid it setting, and programs designed for oven dishes heat up too soon for raw egg.

Wooden items can be dishwashed, but the wood surface slowly deteriorates over many washes. OK for a one off wash of tools, or for low value disposable goods such as cooking spatulas.

Other uses

Cleaning many diy items


Goods can be descaled in a dishwasher by putting citric acid in the detergent dispenser instead of detergent.

Electrical goods

Despite the usual advice to never mix electricity and water, a wide range of electrical goods and parts can be dishwashed. However its essential to choose correctly which items can and can't, and also necessary to use a safe drying procedure, which isn't as simple as leave till touch dry.

This should not be attempted by anyone without the necessary electrical expertise to do it safely.


The art of dishwasher cooking has a small cult following. Care is necessary to avoid washwater & detergent contamination.

Not able to

Dishwashers do not sterilise items.

One use we can't really recommend is cleaning the toilet seat by putting it in with the dishes. Apparently this was actually done in one US restaurant. Yum.

Glass etching

A small percentage of glassware slowly gets etched, going cloudy. Some lead glass is vulnerable, some isn't. Its caused by the hot alkali, and there's no remedy other than not dishwashing it, to avoid the cloudy area growing.

Its also possible to get hard water desposits on glass if salt & rinse aid aren't used. These come off with acid, eg vinegar.


The author has used various brands of detergent tablets from cheapo to expensive brands, and has never found any noticeable difference in the end result.

Separate detergent and rinse aid is cheaper than most brands of detergent tablets.

Dishwasher detergent is also very good at cleaning hobs, sinks etc. Use it with hot water and avoid skin contact, it can cause chemical burns.


Only use dishwasher salt. Other grades are much too impure, and stop the ion exchanger working, causing scaling & water spotting.

All in one tablets contain something to soften water, but it doesn't have the same end result as the salt in the salt reservoir (which refreshes the ion exchanger). The salt reservoir still needs to be filled, unless your water is totally soft.

Rinse aid

One uk.d-i-yer says his machine cleans fine with no salt or rinse aid. Some certainly don't.


  • Clean filters
  • Ensure the machine has salt in the reservoir
  • Unblock spray arm jets & check they rotate ok
  • Acid clean the machine

When it doesn't clean

When a dishwasher doesn't clean stuff off, the following can be used:

  • An overnight soak in water before dishwashing removes a lot of muck
  • A 2 day soak in bleach removes more resistant muck
  • Cleaning ceramics, glass & plastics with hydrochloric acid removes just about everything else, including rust marks
  • Vinegar soaking removes a range of muck films on stainless steel pans & cutlery
  • Spots of rust & muck on steel can be removed with a copper scourer or a brass brush in a die grinder.
    • Avoid steel scourers & brushes, they scratch steel

Cleaning the dishwasher

Proteins form a gloop that accummulates in some hidden parts of the machine, causing smells, bacterial & mould growth and sometimes machine failure.

Ordinary washing up liquid removes muck dishwasher detergent doesn't. A few drops of it in the machine before starting avoids buildup. Don't overdo it.

Acetic & citric acids tackle both protein gloop and limescale. These need to be used without the usual detergent, which is alkaline.

They are far more effective used hot than cold. For it to work hot requires delaying its release into the wash water until the main wash cycle, as the initial rinse is cold. Ways to do this include:

  • putting acid powder in the detergent drawer
  • or using a commercial delayed release dishwasher cleaner bottle. These use a wax insert under the cap to open only when hot. But the cost is several times as much.

Child safety

Dishwasher detergent is alkaline, and need to be kept well away from young children and animals.

Liquid pouches in particular have caused A&E admissions. They look a bit like sweets, and have a great texture to chew on, until it bursts in the mouth. Child then ends up with a tube down their airway for a week until the swelling goes down, and in some cases operations have been required to reconstruct the throat.

Smell & mould

Closing the door for days with dirty dishes inside causes mould & smells. Leave the door ajar and this doesn't normally happen, the air circulation dries the dishes and prevents it.

See also