Is Calgon Worth Using?

A lot of people want to know if Calgon (or a similar anti limescale product) really works. More importantly do washing machines really “last longer with Calgon” as their adverts insist they do? The short answer is clearly the products must work as advertised but it’s more complicated than that.

They will help prevent limescale, and limescale definitely damages washing machines. But in theory at least you shouldn’t really need anything other than the washing machine detergent.

So washing machines can last longer with Calgon, but that doesn’t mean they can’t last longer without it either – as long as you use good quality detergent and the correct amount of detergent for the type of water in your area.

Manufacturers of washing machines and detergent (indirectly) say that you don’t need anything to protect from limescale other than detergent. Here are some examples from washing machine instruction manuals –

Too little detergent results in limescale on the heating element

Rule number 4: Use the right amount of detergent. Too little will cause poor wash results and a build up of scale

This obviously means that using enough detergent will not result in limescale. Here’s a different quote from a users guide to looking after your washing machine produced by Persil, which goes further –

One of the things that can damage your washing machine is the build up of scale, particularly in hard water areas. But if you use Persil Automatic at the correct dosage you won’t need any additives to help protect your machine from scale

So washing machine detergent already contains ingredients to soften the water and protect the washing machine from limescale.

If you use a good quality detergent, and the correct dosage for the hardness of your water and the level of soiling on the laundry you should not need to use anything extra.

If you are getting limescale problems then you probably aren’t using enough detergent. I have to say though that as so many people seem to under-dose with detergent maybe Calgon does a good job of helping such people protect against limescale when they persuade them to use their product.

Calgon softens the water

It’s advertised as a limescale preventer. Technically it is, though it doesn’t do anything different to the softeners in detergent (which they do state clearly now on their web site). It simply softens the water, the same as detergent does.

One advantage is that you can then use less washing machine detergent. However, that would only make sense if the combined cost of Calgon and the reduced amount of detergent was less than the cost of the full dose of detergent alone. I doubt that it is though.

Can limescale really shorten a washing machine’s life?

Limescale damage on a heating element
Limescale damage on a heating element

Yes there’s no dispute about that, it can rot seals and insulate the heating element but these effects usually take a long time to become a problem. The controversy over Calgon is any idea that if you don’t use Calgon it will shorten the life of your washing machine.

Also, does limescale really shorten a washing machine’s life as quickly as most people might assume? Which? have recently submitted a complaint to the Advertising Standards Authority, asking it to investigate the claims made in Calgon’s adverts after their tests showed that washing machines do not succumb to masses of limescale and break down if Calgon isn’t used.

I’ve stripped down many old washing machines that were covered in limescale inside – caked in it – but were still actually working. The heating element can become covered in it but many still soldier on. However, any coating of limescale on a heating element will have an insulating effect. That will reduce the amount of heat produced, and increase energy use and wash times.

It can also causes hot spots, which can cause a heater to fail. Limescale is more of an issue in very hard water areas. In areas with soft or moderately hard water it can take many years for limescale build up enough to cause a break down. Many modern washing machines just don’t last long enough for limescale to cause a problem these days.

In September 2011 Which? also published an article in their magazine entitled, “Calgon’s own research matches Which? findings”. They reported that Calgon themselves have found it takes at least 3 years to show signs of significant limescale damage, by which time you would have spent £170 on Calgon (2011 prices). I think it’s safe to assume this is in hard water areas, so soft water areas would presumably never show any signs of breakdown due to limescale.

Do not use in soft water areas

There could be many people using Calgon who have relatively soft water and could therefore be softening the water in their washing machine too much. This is because Calgon has often been advertised in areas with soft water, and their hard water checking tool was “faulty” (see next paragraph) for many years. Apart from being a waste of money, water which is too soft is not good for washing laundry. It can cause excessive soap suds, poor wash results, and even prevent detergent from being dissolved properly.

Check if your water is hard or soft

If you are concerned about limescale you need to know exactly how hard or soft your water is. For many years Calgon’s website had a post code checker tool. It checked the hardness of the water in your area by post code. I was initially impressed with this, and even considered linking to it, but when I entered my own post code I received a full red bar pointing up to “hard”, and the following message –

HARD – We recommend using Calgon in every wash to prevent limescale build up in your washing machine

As I knew we had fairly soft water I sent them an email pointing this out and asking them to look into it. The tool was clearly “faulty” (at least with my post code).

Even though they acknowledged receipt of my e-mail and claimed they would look into it, the erroneous advice was still there over 6 years later. Unfortunately I was left feeling they couldn’t be trusted to advise on whether you have hard water or not.

Fortunately they’ve now dropped this tool and just use a UK map with large red areas highlighted. However, when I contacted Yorkshire water to double check the hardness of my water they told me that post codes were an unreliable way of accurately determining water hardness.

Free water hardness test kits

Although Calgon have an online form that you can fill in to send off for a free test kit I sent for one through my local water company. Ironically, when mine arrived, it was supplied by Calgon. It consisted of a small strip to dip into the water which would indicate the hardness of the water. Sure enough, it showed my water is soft. So this at least implies their proper physical testing kit can be trusted.

Summary regarding Calgon tablets (or similar products)

Products such as Calgon don’t do anything that proper washing machine detergent doesn’t do (as long as you use the correct amount) but they do the following –

  1. Help protect against under dosing
  2. Soften the water allowing you to use the amount of detergent recommended for soft water in a hard water area

The last effect could potentially save money if the money saved by reducing the amount of washing detergent is greater than the cost of the Calgon (or similar) tablets. I don’t know of anyone who has done the appropriate tests to determine this but Calgon claim you could save up to 25% of the amount of detergent required. 25% is presumably the best case scenario, it depends how much the tablets cost compared to how much you save in detergent. The calculation you need to do is, if you used 25% less detergent but started paying for 1 Calgon tablet in every wash would you save money?

Why do some manufacturers recommend Calgon?

A few reputable washing machine manufacturers recommend Calgon. Calgon’s site lists 6, but because some of them are the same manufacturer making different brands (eg, Electrolux, Zanussi and AEG) there are only really 3. I was initially puzzled as to why because, if it was really so necessary and useful surely all brands would recommend it? But conversely, if it really was unnecessary, then surely no brands would recommend it?

Of course recommending any product to all new customers is likely to be a commercial arrangement, but I can only assume they are recommending it because they would rather people use Calgon tablets and be more likely to keep their washing machines free of limescale (and working) due to the fact so many people don’t use enough detergent.


Some people do indeed suffer from problems caused by limescale and I occasionally come across people who claim to have used good quality detergent and always used the right amount but still have limescale problems in their washing machines. This appears to contradict some of the advice in this article. There’s no way of knowing how accurate their anecdotal evidence is but in the interests of balance here’s a link to one such case – Limescale

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3 thoughts on “Is Calgon Worth Using?”

  1. My Miele recommend a superheat wash with nothing but detergent and it really works. I found it on white goods care site.

  2. I use Calgon in every wash, and have done so in the same machine for over 11 years.
    The machine was second hand when I bought it, ex rental, so it is 12+ years old.
    My last two machines failed due lime-scale build up on the heating element in under 3 years.
    The small additional cost per was has been more than offset by the fact that I have not had to buy 3 new machines.

    Plus it also does act as a descaler.
    During use scale brakes off, but if no (of insufficient) softer is used it it then replaced by new scale. Just look in the bottom of kettle in a hard water ares, lots of lose bits of scale and the element and sides are still covered. The scale is falling off as fast as it forms. That is why kettles have a filter on the spout, to keep the scale out of your drink.
    With Calgon the scale still falls off, but is not replaced. Eventually most of it falls off, especially in the case of the element, which is subjected to increases in temperature, and expands/contracts.

  3. Hi Mark. No one says Calgon doesn’t work, what’s in question is how necessary and or cost effective it is bearing in mind detergent does the same job. The trouble is many people don’t use the correct dosage of detergent so they get limescale.

    Even Calgon say it’s not a descaler –

    “Calgon has a unique formulation with active ingredients being polycarboxylates which softens hard water, preventing limescale from forming in the first place. It is not a descaler, it is purely a preventative ”

    Consumer group Which? extensively tested it and said –

    “We found no convincing proof that washing machines really do ‘live longer with Calgon’ when we put it to the test.”

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