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Re: DIY deionizer

> Date: Thu, 1 Nov 2001 19:22:17 -0500
> From: "Joe Kopanski" <kopanski at earthlink_net>
> Subject: DIY deionizer
> Iím looking for advice on building a water deionization system for plant +
> S.A.
> cichlid tanks.

Don't. <g>

> My plan is to create a three-stage system:  1) Granular activated carbon
> (GAC) cartridge, 2) Anion resin, 3) Cation resin.  I plan on using the
> deionzer chambers from Cole-Parmer ($75 each) plus anion and cation resins
> from Spectrapure ($85 and $41/gal respectively).  While the resins are color
> indicating, Iíll also make a resistivity probe for my voltmeter to measure
> water quality.

A $15 pocket tds (total dissolved solids) meter from Hannah Instr. is likelier
to work. Electrolysis and other problems actually make DIY probes rather
difficult to make, unless you have a high-frequency ac Ohmmeter. There are
also cheap little green/red LED in-line indicators for water treatment
monitoring. They change when the water drops out of the megOhm range.

> The main reason I want to build my own DI unit, is so that I can plumb it
> for very easy recharge.  

RO (Reverse Osmosis) units do it without *any* need for recharge, at far, far
lower cost. That's particularly true if you salvage the waste water. I used to
hook mine right into the patio-drip-irrigation system. [It is only a few
percent higher tds than the tap water.]

> I plan on plumbing it so that I valve off each
> deionzer chamber when exhausted and gravity fill with recharge solution.
> After recharge, Iíd gravity flush a 5 gal carboy of DI water through the
> chamber, through a marble chip bath, and down my household drain.  While my
> initial cost will be high, I hope to have a portable, high capacity source
> of high purity (< 1 ppm) water that can be recharged cheaply, easily, and
> ďforeverĒ.

Provide for major dilution of those recharge solutions, first, for many water
departments now have sewer alarms for anything strong enough to affect the
treatment process. You don't want an environmental swat team in your yard. ;-)

Under current requirements, I'm not sure if that dilution/cleanout water
doesn't approach the waste water produced by efficient, modern RO units! By
coiling 30' of poly inlet tubing in the warm closet, housing my water system,
I turned a 10 GPD system into more like a 30-50 GPD unit, BTW. RO efficiency
goes way up with both pressure and temperature. Attic pre-heating would work
in many homes, too.

Your initial cost is many times what I have paid for RO units. The fuss is
much less with them, while the output water is "safer." 30-50 ppm of tds is
enough to help prevent tds shock and buffer the pH a little bit. IMHO, that's
probably as "pure" as water for fish and plants should ever be.

DI water (and distilled) must always be cut with some tap water (or
reconstituting salts) to be safest for fish or plants, except when used as
simple top-off for evaporatiion, etc. It just creates too much osmotic
pressure drop across the cell membranes, and can even burst them under some
circumstances (like abrupt tds reduction).

> Will my recharge scheme work?

Yep. Sounds OK. Just a lot of extra work and $$$. 

I have arranged two food-safe barrels to receive slow discharges from my RO
and tap waters, with a swamp-cooler cutoff valve on each. [Dry carpet policy.]
Both are fed from a refrigerator-ice-maker saddle valve on the cold line under
a sink. Drip-irrigation valves regulate the flow at each system (and make
annual cartridge changes easy). The newest RO unit came with triple-carbon
filters, and I installed two more in series to the "tap" barrel. A 10 GPD RO
unit let me have ample water for about 150 tanks and smaller containers for
killies. Everything is available at warehouse stores, at reasonable prices.

> I plan on connecting directly to my cold water line and flow control by
> adjusting the cold water faucet.  Will my city water pressure be enough to
> drive a filter housing and two DI chambers in series?  The DI units are
> rated for 15 GPH.

That could be a bit *too* fast for the carbon filter to extract much
chloramine, or even chlorine. I guess that might mean much more frequent
recharges if the ion beds saturate. Slow flow is better (carbon adsorbs huge
amounts of chloramine under slow flow and tap pressures), so intermediate
storage is a must if you have many tanks to service. I just used a waterfall
pump, in either barrel, on the end of 60' of vinyl tubing to reach any tank in
the house. X-10 remote pump switch and hose valve and sprinkler on delivery
end automated the process of tank-to-tank changes. Lifting the pump from one
barrel to the other permitted "mix-and-match" to any water tds desired.

> Iím thinking a GAC cartridge is the way to go, since I donít think I need to
> filter out particles less than 10 microns.  Is a carbon block a better idea?
> But would I need a pre-filter to keep the block from clogging too soon?

Probably. It would depend on how low the turbidity is in your tap water.

Sorry to sound negative. I think you have a good project that will provide
lots of processed water. Having been there, done that, I just wanted to share
my perceptions. I had 30+ years of facing the same problems for processing
water in my holography company. As you can see, I'm sold on the cost,
reliability and convenience of RO. [I've used both systems, a lot, BTW.]

There are several good suppliers of complete RO units to aquarists. They cost
a bit more (not much) than Home Depot, but provide ample expert support. The
one I know best is Dr. Ron Harlan, Back-To-Nature Aquatics in Glendale CA.
There is another in AZ that is highly regarded, but IDK the name. Ron
advertises in the big mags, but didn't have a web presence, the last time I

Good luck,


PS A point of aquatic philosophy: 

I don't mind the time and effort of doing water changes, feeding my fish,
trimming plants and vacuuming up mulm. I'm viewing and interacting with them
right when I do it, and it disciplines me to keep an eye on them before things
go bad. We both benefit.

Repetitive tasks that do not create that direct interaction need to be
minimized if we have any limits on our hobby time. Changing filters,
recharging ion-exchange chambers and responding to list questions fall into
that category, IMHO. ;-)

[Easy for me to say. I just moved and have no fish or plants, right now. WH]

Wright Huntley 510 612-1467 - 879 Clara Drive, Palo Alto CA  94303

   "You need only reflect that one of the best ways to get
   yourself a reputation as a dangerous citizen these days is to
   go about repeating the very phrases which our founding
   fathers used in the struggle for independence."
           --   Charles A. Beard (1874-1948), U.S. historian