[KCguy]

Ive got my RO system setup and I want to begin harvesting yeast, but heard that RO water is a little acidic.  In fact, mine is testing out at ph9.  Is there any harm being done to the yeast if I use RO water to wash it with? 

[narcout]

Check this out:

https://www.homebrewersassociation.org/forum/index.php?topic=19850.0

[KCguy]

I will read that right now, but I shouldve been clearer - I dont plan on rinsing, only adding some water to the trub/yeast cake so that it comes more easily out of the fermenter, rather than in globs and sloppy clumps.  Maybe later, after seperation, I might use a turkey baster to pull off the yeast suspension, and leave the trub behind.  But for now, just to salvage the cake, Im adding water to get it all out of the fermenter...

[Robert]

Nope.  That's enough water to introduce all the problems with yeast rinsing.  Don't add water.  Plan ahead to leave enough beer behind to harvest the yeast.  Water + yeast = many detrimental effects to the yeast.  BTW there are significant negative effects of watering yeast not covered in that thread,  but it is an admirable thread indeed.

And don't be scared of a little trub carried over, even when you repitch the yeast.  It won't grow, only the yeast will.

[denny]

I will read that right now, but I shouldve been clearer - I dont plan on rinsing, only adding some water to the trub/yeast cake so that it comes more easily out of the fermenter, rather than in globs and sloppy clumps.  Maybe later, after seperation, I might use a turkey baster to pull off the yeast suspension, and leave the trub behind.  But for now, just to salvage the cake, Im adding water to get it all out of the fermenter...

You're better off using beer than water.  That's advice from a friend who learned it at Siebel.

[denny]

Nope.  That's enough water to introduce all the problems with yeast rinsing.  Don't add water.  Plan ahead to leave enough beer behind to harvest the yeast.  Water + yeast = many detrimental effects to the yeast.  BTW there are significant negative effects of watering yeast not covered in that thread,  but it is an admirable thread indeed.

And don't be scared of a little trub carried over, even when you repitch the yeast.  It won't grow, only the yeast will.

Great minds, buddy....

[kramerog]

I use Miller High Life Light to get the yeast out or whatever I have on hand to offer the non-craft drinkers.  I think the High Life Light will be 2 years old in August. 

[MattyAHA]

ok, to sum up everything i learned on this thread and other threads, do not wash yeast, do not add water, simply decant the slurry into a sanitized vessel trub and all with the beer, correct?

[KCguy]

I usually end up with about 5.25 g per batch, so that I get right about 48-54 bottles yield.  Are you saying to pull out less beer to bottle with, or add water to the cooled wort so that I end up with something like 5.5 gallons?   

Id prefer to simply pitch a new batch of wort directly onto the legacy cake/trub as many have advised, but my bottling days dont usually coincide with brewing days, so I doubt I'll ever be able to do that. 

[Robert]

I plan my post boil volume so I'll leave enough beer behind after kegging to harvest the yeast, a good quart or two at least, but how much will be up to you.  Who advises pitching new wort onto the cake?  I've heard of it being done but bad idea.  You'll be way overpitching, and really carrying over a lot of trub, among other things.  Leave beer on the cake, swirl up and dump into a sanitized container,  when ready to pitch you can pour some of the beer off, swirl, let trub settle for a minute or two if you want, and pitch as much as needed.
 

You can also separate some trub at harvesting by letting it settle for a few minutes before pouring off into your container.   Since your yeast cake will be at least 4 times what you need to repitch, you can lose a bit at harvest and at repitching.

[Robert]

I use Miller High Life Light to get the yeast out ...

Hey, now the 40 oz makes sense....  Actually this sounds like a great tip.  Beer is beer in this application.

[Richard]

heard that RO water is a little acidic.

Technically, RO water is a perfect pH 7.0, which is the dividing line between acid and base, so it is neutral on that scale. What you may have heard is that it is corrosive, which is true. Another way to phrase it is that there are lots of things that will happily dissolve in pure water at a much faster rate than they dissolve in "normal" water.

[Robert]

Another way to phrase it is that there are lots of things that will happily dissolve in pure water at a much faster rate than they dissolve in "normal" water.

One problem with water in the context of this thread is that lots of things want to dissolve in any water.  But exposing yeast to any water will always present the situation of a lower level of dissolved solids outside the cell (water) than inside the cell.  This will cause the yeast to, in simplest terms, spill its guts, as the stuff inside tries to get into the water.  Rapidly turning inside out is of course not a pleasant thing for yeast any more than it would be for you.  The cell walls may not rupture instantaneously, so a minute or so of exposure right at pitching (if you really feel a desperate need to thin the slurry with water or separate trub at this point) may not seriously compromise the viability of the yeast crop, but any longer exposure or storage of yeast in anything other than beer will.  Thanks to ToddH for pointing this out on a recent thread.

[hopfenundmalz]

heard that RO water is a little acidic.

Technically, RO water is a perfect pH 7.0, which is the dividing line between acid and base, so it is neutral on that scale. What you may have heard is that it is corrosive, which is true. Another way to phrase it is that there are lots of things that will happily dissolve in pure water at a much faster rate than they dissolve in "normal" water.

If you expose distilled water to air, CO2 will difuse in, the carbonic acid formed drops the pH to about 6.5.

[denny]

ok, to sum up everything i learned on this thread and other threads, do not wash yeast, do not add water, simply decant the slurry into a sanitized vessel trub and all with the beer, correct?

Exactly.