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Re: cellar chemistry #1

Hello Kevin,

The right way out of your problem (assuming the conditions you have set
up, i.e. 1 gallon eveporation and 1 gal. water change) is to add 1 gal.
of the reconstituted RO water (to replace the water change) and then 1
gal. of RO water (to replace the evaporated water).

That way your conductivity should remain constant over time. 

Of course. you can make up the reconstituted RO water with 1/2 of the
salts and just add 2 gallons of that half-strength water!



> Date: Fri, 2 Jun 2000 20:03:46 -0400
> From: "Kevin Zippel" <kczippel at worldnet_att.net>
> Subject: cellar chemistry #1
> As I said in a previous post, I never worried much about tap-water quality
> until it was a problem.  Now that I have studied it and understand it
> better, I worry about it a lot!  [ignorance is bliss?!]   At first, I was
> using RO water just as a base to reconstruct tap water.  But after I went to
> great extremes to get the initial concentrations of all the ions just right,
> evaporation would go and mess it all up by changing the concentration of
> water around my ions!  Should I then be topping off with RO water before I
> do water changes, to bring all those ions back to their original
> concentrations??  Evaporating water presumably leaves its dissolved contents
> behind, concentrating the water in the tank.  Adding pure RO water would
> seemingly bring it back to its original concentration, but adding
> reconstituted water might make it more concentrated with solutes (harder,
> saltier) with every top-off.  The purist in me had to know how significant
> this factor really was.  [yes, I have way too much spare time]  I set up the
> following basement experiment:
> Three 5-gallon buckets were filled with tap water and churned with an
> airstone.  When each had lost 1 gallon (20%) over time to evaporation, they
> got one of three 'water change' treatments.
> - - bucket 1 represents the lazy aquarist; the evaporated water was simply
> made up for with straight tap water and no water was changed.
> - - bucket 2 represents the avaerage aquarist; after 1 gallon was lost, a
> second gallon was siphoned out and the 2 were replaced with straight tap.
> - - bucket 3 represents the anal aquarist; the evaporated gallon was replaced
> by an RO gallon before a 1 gallon water change using straight tap.
> 'Concentration' was measured with a PinPoint conductivity meter.
> Measurements were taken 1 day after water changes, as conductivity rose
> significantly over the first 24 hrs.  [I don't know why it would, perhaps
> dissolved gases have some effect, but it did stabilize after a day, so I
> took all measurements only after 24 hrs]
> It's been 1 month and I just did the 3rd water change.  Here's the deal thus
> far:
> date     bucket 1     bucket 2     bucket 3      tap
> 5/2       start
> 5/3       215             215            215             215
> 5/13     fan added for forced convection (I got impatient!)
> 5/16     water change #1
> 5/17     261             251            218             221
> 5/24     water change #2
> 5/25     279             259            207             227
> 6/1       water change #3
> 6/2       300             275             205            227
> In just 1 month (granted, with forced convection), the lazy aquarist had
> raised conductivity by 40%.  The average aquarist raised conductivity by
> 28%.  The anal aquarist actually lowered conductivity (I'm guessing that's
> explained by the 'salt' stains above the water line).
> Interesting.  Probably not as much an issue for the keeper of planted tanks,
> where presumably many of those extra ions are used by the plants.  But it's
> food for thought/discussion.
> Kevin [really bored in Detroit] Z.