The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Water for starter - PH and reverse osmosis

perry's picture

Water for starter - PH and reverse osmosis

My ph is 7.4 - does this matter in bread making.  Also is it okay to use RO water

FoodFascist's picture

Hi there,

I'm not sure about pH - I know generally very alcaline water isn't great but don't know how critical your particular pH reading is.

From what I know about RO though, it's not far off being distilled - i.e. very poor in minerals, which isn't actually that good for you. It'll have an impact on the taste, too, but whether big enough for you and other eaters to notice is to be seen. TBH I'm not sure why people bother with reverse osmosis filters, they are comparatively expensive to run, have the lowest output of all filters (only about 65% if I remember correctly?) so a lot of water wasted, and besides the water they produce is devoid of essential minerals. Much better to install an ordinary filter and if your water is also too hard, a magnetic conditioner. IMHO.

RO water may also be quite soft, I remember lumos here talking about the effects of very soft water on dough structure but can't remember exactly what those effects were, hope she'll jump in soon.

LindyD's picture

Per Bread, water that's slightly acidic (pH just under 7) is preferred for bread baking.  Your reading is slightly alkaline which could decrease yeast activity.  Fermentation just may take longer.  Take heart that it's not 8 or 9.

I would avoid RO water, though.  It's stripped of minerals, and minerals supply food for the yeast.  You can do a search here using "reverse osmosis" and you'll come up with a number of discussions on that topic.

If you use your tap water for cooking and drinking, use it for your bread.  If you are on city water and it's treated with chlorine, just fill a container the night before and let it stand (uncovered) overnight and most of the chlorine will dissipate.  

sam's picture


Respectfully, I believe it is a fallacy that yeasts+LAB need anything more than just plain H2O and flour food.  

I exclusively use distilled water for my SD culture, levains, and breads.  Here's what it looks like.



It provides great leavening and flavor.  The flour provides all the minerals it needs.

And there's nothing wrong with drinking distilled water.

MangoChutney's picture

We recently bought a water still and are very much enjoying drinking the distilled water we get from it.  Our well water is very hard, and alkaline enough that it only needs a little salt to be called brackish.  In late summer it sometimes tastes fishy, which I attribute to the actual fish in a nearby pond which probably taints the groundwater when there has been too little rain.  It is a relief now to always have clean water to drink.  I have been using the distilled water in my bread.  It still rises, so I guess the yeast don't need the minerals in the well water.

Doc.Dough's picture


I concur. In fact I bake with RO water exclusively.  The TDS level is consistently around 6 ppm, it works just fine, and the pH is really hard to measure because the conductivity is so low. Once I mix water with flour the pH goes to around 6 and continues down from there until the LAB stop metabolizing. See link below for data.

I suspect, but have no personal experience to confirm, that if your municipal water supply delivers free chlorine to your tap then you may have problems. If that is the case, then a simple activated carbon filter will strip the chlorine and fix the problem. I suppose that highly alkaline water might pose a problem but it would be more likely from a local well than from a city supply where there is monitoring and some semblance of quality control.


Rosalie's picture

I am determined to get back into sourdough.  My first step is making the starter.  I have reverse osmosis water.  I do not use it for baking yeast bread because it does not give me good results.  But can I use reverse osmosis water (NOT just filtered or distilled, but reverse osmosis, which is virtually pure water) for making and maintaining the starter?


Edit:  Okay, I guess the terminology has me confused.  But what I have is RO, and I want to know if I can use it for my starter?

thomaschacon's picture
thomaschacon (not verified)

It's just water devoid of trace amounts of ions and minerals.

Not sure I would drink a lot of it, but should be fine for cooking/baking/starter maintenance/etc. Once had distilled water delivered. My stomach did NOT like that at all. Worst stomach ache ever. No idea why, but lesson learned.


I've never killed a starter using even plain ole' tap water. I currently use a Brita filter water pitcher.

All at Sea's picture
All at Sea

Another vote for RO being just dandy for bread, starters, the whole dough ensemble!

Live on a boat, so we have to either catch our own water (rain) or make it - courtesy of a watermaker. That means reverse osmosis H2O.

No problems with RO water, promise you - it will keep your wild yeast in liquid nirvana. Been using it to make starters for over two years. Nay worry, lass!

All at Sea

Doc.Dough's picture

A reverse osmosis (RO) filter has pores that are so small that only H2O-sized molecules can make their way through, along with very small quantities of very small ions.  An RO filter is generally preceded by a particle filter that removes sediment down to 5-20 microns AND an activated carbon filter to remove chlorine (because chlorine will damage the polymer membrane that makes up the RO filter).  The carbon filter also removes some dissolved gases.  You can use a TDS meter to measure the quality of RO water (it measures total dissolved solids by observing the conductivity of the water, but it only measures those dissolved solids that ionize so it won't find sugars or proteins). Anything below ~20 ppm TDS is pretty good.  Above that, suspect your filter to be leaking.  If you don't like the flavor you can always add back minerals to "improve" it for drinking. Calcium, magnesium, bicarbonate and sulfate are commonly found in mineral waters (and tap water) at concentrations of up to 500 ppm or higher.

All at Sea's picture
All at Sea

... you say "If you don't like the flavor you can always add back minerals to "improve" it for drinking.", Doc. If the watermaker is doing its job, there is no flavour. I guess some folk might not like the absence of flavour, is how it goes.

Yet to me, a long full glass of ice-cold RO water is absolute nectar on hot days. Crystal clean, no whiff of chlorine, no hint of any odour - no absolute nuffink! Just pure hydration at its cleanest and most refreshing.

Because we get all the nutrients we need in food, the lack of mineral content in RO won't hurt you.  You'd have to be in a startlingly low-nourished state to suffer from the 'emptiness' of RO water. We've lived off that and rainwater almost exclusively for 3 and a half years now. Still tootling; still healthy in wind and limb.

All at Sea

dabrownman's picture

RO, bottled RO and bottles of spring water, as well as, tap water that has been allowed to sit for a a few hours to allow the clorine to disapate.  All work equally well for me.  Maybe the bottles spring water has better spring in the oven but I can't prove it :-)

Janetcook's picture

I use RO water only for drinking and cooking and my leavens thrive on it. 

Good Luck :-)