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[SimonCornes]

Thats it - what do you use to avoid lime scale build up? I started using de-ionised because thats what the local car accessory shop had and it's also used for electric irons apparently. But someone said recently that I should be using distilled water instead so I have a gallon of that on order! Can someone give me the benefit of their experience please ??
Thank you

[DBS88]

Simon, the issue is to avoid limescale build up, so it depends where in the Country you are as to how much of an issue hard water is. For example, where I live the water is drawn from chalk aquifers and is hard so limescale buildup will foul my boiler very quickly, however, my daughter lives in Scotland, the water there is soft, no limescale, so tap water there is probably fine, but a complete no no in the Southeast of England.
Probably the best, cheapest source of water for your boiler is rainwater - it's soft, just run it through a filter to remove any dirt. Next if you have a dehumidifier, the water from there is also soft, so again a good source.
Then true distilled water - unfortunately the terms distilled water and de ionised water are being used interchangeably so be careful.
My understanding is that de ionised water tries to reclaim the ions and it does this from the things it comes into contact with, in our case brass boiler fittings, the so called dezincification of brass, which leads to the fittings failing. I am not a chemist or metallurgist so could be completely wrong

[SimonCornes]

I was told that rainwater was a good substitute if you didn’t have de-ionised or distilled but, going by my electric kettle where I do get scale then tap water is sadly not an option where I live. So the question still stands- de-ionised or distilled?

[rhavrane]

Bonjour,
As mentioned by David, deionized or distilled water wants to get ions back so attacks metals, so I would kindly suggest you to use sometimes "normal" tap water or add a drop of it in your deionized or distilled water.
Hopefully, ionization is not a short term effect, they can be possibly visible after years, I don't know if you have seen my topic:
https://www.modelboatmayhem.co.uk/forum/index.php/topic,70548.0.html

[Bunkerbarge]

Distilled water is simply the result of evaporating, or boiling to speed it up, water and then recondensing the vapour into a liquid.  This is a useful method of cleaning solid particles from water and is used in many industrial plant for that purpose.  The resultant water is simply cleaner than the original.


De-ionised water on the other hand has had ions removed.  The ions are molecules with a resultant positive or negative electrical charge and in water they make up most of the dissolved salts.  The process of de-ionising the water, using ion exchange, actually makes the water more chemically consistent by removing minerals but it leaves behind uncharged contaminants such as bacteria, viruses and other products.  De-ionised water is used in lead acid batteries because it is chemically more consistent and filtration removes the remaining contaminants.  It is a better electrolyte than distilled.  This is the very reason that makes it more harmful to metals as it can leech ions out of any metal it comes into contact with.  As with many of these things however it only takes place over a prolonged length of time.


To answer the question distilled water is better for boiler use.  De-ionised would be unlikely to cause any damage unless used for a long time but then it could and copper is one of the metals that are susceptible. The easiest sources of distilled water to us as modellers would be 1) filtered rainwater, 2) filtered tumble dryer condensate and 3) filtered de-humidifier condensate.  If you are lucky enough to live in a very soft water area, such as Scotland or West Yorkshire, tap water would be fine but if you live in a very hard water area such as most of the south of the country (and Lincolnshire is appalling) then I would use one of the alternatives above.

Simple answer, distilled.

[SteamboatPhil]

Not sure if it is still the case but some chemists used to sell distilled water.

[tonyH]

Even Amazon sell it. Look for the words "STEAM DISTILLED"

[1967Brutus]

De-ionized water is a bit of a misleading term. "De-ionizing" is done by means of an Ion-exchanger, and what happens is that the scale forming ions are exchanged for non-scaleforming ions. But the amount of Ions (positively or negatively elctrically charged particles) of the water remains unchanged.

Hence, the water is still elctrochemically active, causing the de-zincification. It does not cause scale as a plus, but it causes brass to become brittle and porous to some extent. This is a slow process, but after a number of years, brass parts become unreliable.

Destilled water does not do this: There are NO (or barely any at least) ions in destilled water, not scaleforming nor non-scaleforming. Hence no electrochemical activity, and no scaleforming.

In copper boilers, de-ionized water is all you need. IF the boiler and its fittings are made out of copper. Chances are, boiler and fittings are made of brass. Then destilled water is preferrable.
In steel boilers that are very frequently used, you need a pH above 8 (preferrably 9 or more) and an oxygen scavenger, otherwise you will see pitting. Steel boilers not in use, best are stored with treated water, and topped up so there is no more air in it.


You can buy destilled water, but home-destillers are fairly cheap to buy (around 100 Euro gets you a decent one). Takes quite a while to earn it back, but the convenience of having destilled water at will is worth something as well.
My local tapwater is roughly 200 ppm Total Dissolved Solids (TDS), my destiller gets that down to about 7~10 ppm in the first run, less than 2 in the second run, pretty close to lab quality. Pretty time consuming though, a single run is roughly 4 hrs for a batch of 4 litres, double that if it is double destilled.
Destillation does a fairly decent but NOT perfect job of removing dissolved oxygen from the water. Not very important in Copper or Brass boilers, but very preferrable in steel boilers. The de-ionisation process does nothing for Oxygen removal to my knowledge.

Without a condenser (water going through the boiler only once), and emptying the boiler, after use, single run destillate is more than good enough, because there is hardly any scale formation happening below 30 ppm and normally, starting with 10ppm, on a once through steam system, 30 ppm is roughly where you'll end up at the end of a run.
I use full condensate return, and using double destillate allows for about 4 hours of operating time before it has thickened to 30 ppm. I do not empty my boiler after use, I refresh the system after four hours of runtime.

[KBIO]

Except to live in the  Gobi desert , a banal bucket left in the garden will suffice for your happiness.
Filter it through a rag to eliminates debris and insects and fill up a jerrycan .  That’s it.
We don’t heat very much for long periods . We do not have the problems of industrial boilers that heat to several hundred bar and high pressure. We are not in a laboratory . There is a big difference between good and better. And often the best is not that good!
Deionized water exposed to air can quickly absorb CO2 and form carbonic acid (H2CO3), which can change the pH of neutral water from 7.0 up to 5.6 . This water is not too good for the brass fitting and other metals . The copper does not fear corrosion .Remember that the pH scale is logarithmic, which is a significant change in chemistry!
Now , you do what you like the best , I am at the pub with my friend  !
 


 

[1967Brutus]

We don’t heat very much for long periods .

My little Microcosm had well over 100 hours of clocked runtime in a little over a year...

[NoNuFink]

 Just out of idle curiosity - I don't build/operate steam - 
Where would water from a domestic water softener fit in this??
Certainly it keeps scale from forming on taps, shower heads etc.  and has not (apparently) harmed the copper pipes in my home during the last 50 yrs.
As I said  Just curious 

[1967Brutus]

Just out of idle curiosity - I don't build/operate steam - 
Where would water from a domestic water softener fit in this??
Certainly it keeps scale from forming on taps, shower heads etc.  and has not (apparently) harmed the copper pipes in my home during the last 50 yrs.
As I said  Just curious

A domestic water softener is basically an ion-exchanger, so that would be de-ionized water.
Copper is usually not affected by de-ionized water, since copper is not an alloy like brass.

[NoNuFink]

      I'll start worrying about all the brass compression fittings and taps then.