Using rainwater in boiler

Hi,

I live in a soft water area - so reading around, it sounds as though I should be able to use tap water in my 3.5" loco copper boiler (I have used it twice already). But it seems rainwater is a popular choice.

We collect the rain from the shed roof into a barrel - so have an ample supply of rainwater. I bought a couple of 25litre water drums and some ultra-fine paint filters and have just filled one drum with "filtered" rainwater. The filters seem to have worked a treat - there are no visible (to the eye) bits in the water, but it has a brown tinge to it and a musty smell.

No doubt if I drained the barrel and waited for a deluge, then I would automatically end up with clearer water - but that's not really practical.

So I guess I'm asking does it matter about the smell/discolouration? Given that it's only for use in the boiler (i.e. not for brewing up with).

Regards,

Mike.

Mike

I don't do anything with steam engines, but on another forum I have seen the suggestion that you take some of the intended water and boil it to dryness in something like a pyrex dish, and see what the remains look like. That way you'll get a good idea of what dissolved solids there are and what sort of deposit you may get on boiler tubes, shell etc. without risking fouling your boiler, which would be a lot harder to clean. The other possibility that comes to mind with material dissolved in the water is that of provoking "priming" through foaming or frothing. Again testing the water as above may let you see if that is likely.

Certainly collected rainwater seems to be looked on very favourably, possibly with more filtering or settling though to get rid of more of the unwanted matter.

Keith

I don't know much about steam engine water either, but I do use rainwater for lots of other things. I would recommend making a simple filter using sand and gravel, this will take out most of the nasty stuff, a good one will make drinking water. Lots on the web but use the usual common sense with some of the ideas.

As a club, and in a hard water area, we always used rainwater whenever possible, and only debris filtered it (leaves and insects etc) through something like a few layers of cheesecloth.

There shouldn't be anything nasty in the water itself, only what it collects on touching materials, TDS or Total Dissolved Solids are a result of water passing over / through high mineral contaminants (ie causing 'hard' water) and in your case, if you are in a soft water area, the only test you need to do is look at the inside of your kettle, if its clean, then its totally suitable to use in your boiler.

The other point to note is that if a boiler containing hard water is 'blown down' properly before fully cooled there will be little or no residual coating on the inside or tubes.

I don't know about paint filters but a coffee fiter would be pretty good. Don't forget that even in a soft water area modern tap water is so processed that is may well be slightly hard - I do get slight deposits in my kettle. Also there will be other residues from the chlorine and SO2 additions depending on your supplier.

I use dehumidifier water as I have gallons but if I forget it the club supply is nicely 'treated' by the leaves that get in. Tannin as from leaves is a standard treatment for full size loco boilers.

The thing to never ever use is 'demineralised' so called distilled water sold for steam irons and batteries.

Edited By Bazyle on 13/03/2014 17:04:01

Hi.

Thanks all. I shall do the boil test and see what's left behind (I remember doing that now at school!). If nothing else, it'll be interesting.

I did think about making a sand filter - but it's something else to have lying about the place. Perhaps I'll look at taking the water off the conservatory roof, at least it'll be fresher and will likely be much clearer once run through the filter mesh.

Thanks again,

Mike.

Is water from a dehumidifier also suitable, assuming you can get enough of it for your purpose?

Andrew M

I use dehumidifier water (and so do colleagues) in car radiators and to top up Lead-acid batteries. And if does not smell either.

A UK shed without a dehumidifier is a shed with rusty tools, sooner or later.

Cheers, Tim

Bazyle, why should one not use demineralised water on model boilers?

On the first generation container steam ships in the 70's, operating watertube boilers at 62 bar pressure, 540 deg.C superheat, we made our own boiler water firstly distilling by evaporation from sea water - which was good enough for all domestic services and drinking water on board. The distilled water was then demineralised before it was deemed good and pure enough to be allowed to be used in our boilers. If it was necessary for those boilers then it should be OK for model boilers surely, or am I missing something - which is quite possible!

Chris

PS  I would have thought dehumidifier water should be fine for use in a boiler.

Edited By ChrisH on 13/03/2014 18:32:07

> The distilled water was then demineralised

The stuff sold for batteries etc. isn't distilled first, just passed through an ion-exchange column, as I understand it.

Neil

The only difference between demineralised water and distilled is that the former is not bacterially sterile.

As this could be used in a boiler and not for potable consumption it shouldn't be any problem at all.

The case for dehumidifier water rather than rain water becomes stronger............!

hi mike, if you live in a soft water area and no scale etc in your club room kettle, i would use the tap water. south wales where i am has excellent water for boilers.

a few sensible precautions are necessary i think in any part of the country ie blowing down the boiler after each steam up. i used to live down south in a hard water area some years ago. ive a paper by Ray Parsons on water treatment in miniature loco boilers if you are interested. water treatment is not dependant on the pH value but on lots of other factors and is quite a complicated subject.

cheers,

julian

Thanks for replies all.

I always (well both times!) blow down the boiler - and the tap water here is definitely soft, so for now I think I'll stick with tap water. Are dehumidifiers are a practical source of water for a loco boiler? Not sure if they'd produce enough.

Regards,

Mike.

Depending on the humidity I get between 3 and 5 litres of water a day on average from my dehumidifier.

Demineralized water is used in industrial boilers all the time.

You can get small water test kits for swimming pools online that would give you a quick read on TDS, chlorides, pH etc for whatever water you decide to use. You never know for sure what rain is bringing down with it, or what it picks up in guttering, tanks etc.

This is what I used to use for the Marine Tank and the guy is really easy to deal with, RO-Man

Easy to set up and you can get a bigger system if you want but the smallest of units will make mare than enough demineralised water for any loco.

graham.

We use rainwater in our club for over 20 years. There is no problem with using it.

Befor we used water from the city water pipe and that was the death of a view boilers. They get many limescale in the boiler and so they overheat partially and the boiler fail.

Since we use rain water we had no problem.

Werner