The Fresh Loaf

A Community of Amateur Bakers and Artisan Bread Enthusiasts.

Use Rainwater to make sourdough?

canuck's picture

Use Rainwater to make sourdough?

Ok, this may be an odd idea, but it just hit me this morning.   I have a rainwater collection system that I use to water the garden.    I was mixing up a batch of dough, and I wondered "What if I use the rainwater instead of the tap water that I normally use?".

So a couple of followup thoughts and questions:

  • Probably people have been doing this for hundreds if not thousands of years.   Its only an odd idea for a city person?
  • Rainwater is going to naturally not have any chlorine, and should be pretty pH neutral (maybe a little acidic?).  Does that make a difference chemistry-wise?  The yeast and bacterias should love this stuff, right?
  • The baking process should kill any nasty bits, my rainwater is stored in large drums and we use it very regularly, and it looks very clear and clean coming out of the barrels (no algea or anything like that).

Anybody done anything like this?  Maybe I should try it and post the results?  Ideas, comments?

Ford's picture

If you live in a smog-free area, then the water is probably fine.  But if the air contains pollutants, then don't use rain water.


Danni3ll3's picture

but there is no way that I would use the water out of my rain barrels to make bread! Especially after I found a dead slug floating in one while using the water to water my plants. And yes, the barrels are covered. I have no idea how it got in there.

Mini Oven's picture
Mini Oven

I'm sure, and trace minerals as well.  Boil & cool first?   :)

I ran water flea thru my Nutri-info checker but came up blank.  :(    So you're on your own with how much their little dead bodies contribute.  The live ones might even eat some of the yeast!  Dig out that dusty microscope and watch the action!  

jimbtv's picture

Stagnant water is rarely safe to drink, especially in our highly-tuned American digestive systems. You also need to consider the entire path taken by those little rain drops before they made it to your collection barrel, and the fermentation that occurs inside the less-than-sterile containers.

I certainly would consider using the water but first I would put it through some purification processes, like U/V exposure, < 3 micron filtration and/or heat treatment. After examining the cost, municipal water might be the better alternative.

kdhowley's picture

I lived in outback Australia for some time, right on the edge of the Tanami desert. The tiny community we lived in used bore water, but it was something I found absolutely undrinkable (super salty!). I'm a pilot and had access to the rain water collection system that collected water off the hangar roof - not filtered in any way that I was aware of. We just used to fill up large containers with this water and used it as our drinking water. Keeping in mind that it's damn hot (42C) most of the year, and for 6 to 8 months there is absolutely no rain. Never had an issue at all. Maybe we were lucky but I'd say if you were baking the water into the bread anyway, you definitely wouldn't have any issues. Where I live now in NZ we are on raintank water too, albeit through a filter - but nothing tastes quite as good as rain water! 


lepainSamidien's picture

Your idea made me think of this video : . . . it's a video of a peasant-baker in France (a guy who grows his own grains, mills them into flour and then makes bread) demonstrating how he makes a new levain each spring.

Basically, he runs a large sheet over the dew that collects on a parcel of wheat on a spring morning. That sheet absorbs the dew, and then he wrings the sheet into a small basin and adds flour to it, from which he creates a new levain.

It's possible that, should there be enormous concentrations of nuisance bacteria in your rainwater, you will have some trouble getting a good levain growing out of it. But as far as safety is concern, it is important to remember that whatever you make with your levain is going to pass through an oven that is pretty darn hot and from which few beasties will make it out alive. On the other hand, the oven won't correct ALL of the off-flavors such a process might pick up.

But why not give it a try ? Pick up some rye flour and go wild.

canuck's picture

Thanks Everyone - great comments.   I'm thinking of doing a side-by-side comparison of refreshing my started and see if the rainwater (filtered I guess, don't want any slugs!) makes a difference to how the starter responds.  I may also try to just bake a loaf.   I have relatives in Paraguay who collect all their water in big cisterns, that's all the water they have and use, and they seem pretty healthy, so it can't be all bad!

Andyhop's picture

Hi Everyone,

Couldn't help but join and chip into this convo as I have very recent (looking at the results right now) experience in this exact department.

Firstly, I also live in Australia on the edge of the Western Australian Wheatbelt overlooking the Indian Ocean. We have amazing air quality, but our scheme water sucks. Consequently we harvest 20,000 Gallons of rain water in 4 enormous rainwater tanks. These are then filtered through two graded particulate filters (down to 5 microns) for our day to day usage in our house, drinking, showering, clothes washing, everything. The water is a soft as water comes, tastes as clean and fresh as any posh bottled spring water and nothing ever has scale on it.

When it comes to bread baking however, there appears to be another story!! It makes the most amazing voluminous sourdough starter, but at the moment, it won't make decent or even usable dough, bread for all tea in china. it is way too slack, full of way too much air, which disintegrates upon looking at it, let alone touching it,and can't possibly be handled without some kind of Jedi mind trick or levitation!!!

I say yet, because these are early days (I'm trying to decide what to do with both my yeasted and sourdough mixes as I type). Some early searching has indicated that very soft water, is ill advised in bread making, as it makes the dough too slack as it lacks the "gluten-strengthening minerals and tend to yield soft, sticky dough" (, yep, been there, looking at that!!

So my next step is to try mixing my rainwater down with scheme (mains) water at different ratios, to try and increase the hardness.

I shall let you know how it goes.

Mini Oven's picture
Mini Oven

set a few small blocks of limestone in your water pitcher or drip the rain water over a block of limestone.  

-An old plantation trick from the West Indies.  The block also cools the water.  :)

Also check on thiol compounds in the TFL archives. 

gerhard's picture

How are you collecting the rain water.  Is it drained off a roof?  I would worry about bird droppings.  You don't just have to worry about live bacteria but toxins left behind by bacteria.  At the very least I would take a sample of your collected water and have it tested for potential issues.  We live in a house built in the late 1800s and it has cistern but even back then the water used for drinking and cooking came from a well the collected rain water was for washing.