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[Amps] water purity/conductivity in water cooled tube amplifiers

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Subject: [Amps] water purity/conductivity in water cooled tube amplifiers
From: John Lyles <>
Date: Sat, 28 Apr 2018 11:37:39 -0600
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I concur with Roger, and have always been taught to avoid using Brass fittings in a high resistivity pure water system for amplifiers. Zinc leaches out, but then again, I don't have systems with routine water replacement, as we use Cuno or Culligan 'resin' beds and oxygen removal bottles in a continuous purification loop. It is done in a sidestream running a few GPM through these bottles, and they are replaced about annually. The main DI system has 100 hp pump and is 950 GPM.

In another building where I have a test amplifier and dummy loads, the water does need replacement every 5 years or so, even with the purification loop. Somewhere in the myrad of pipework, there are some bad materials that will, over time, deposit copper oxide and other coatings inside of hoses and anodes of tubes.


Date: Tue, 24 Apr 2018 11:21:01 -0400
From: "Roger (K8RI)" <>
Subject: Re: [Amps] water purity/conductivity in water cooled, tube, >
We use what we have, what we can afford, and / or what's available.?
That said, brass is one of the poorest metals to use with DI, or
distilled water.
BUT On the positive side, even with monster QRO amps, their runs are of
a relatively short duration.? I've seen around 30, 12KW RF generators?
that have shared cooling water running through them 24 X 7.? There was
the occasional down time for various reasons, but the resistivity was
only checked on a weekly basis.? 24 X 7 That's 168 hours each per week,
but with 30 that cooling system was receiving 5,040 hours per week.? If
the water is changed every 20 weeks, that is roughly 100,800 hours per
water change.? As I remember the water tank was somewhere between 500
and 1000 gallons
"IF" the amp has only a couple gallons capacity and it runs, say 25
hours per week, experience tells me that unless there is something
unusual about the system, "I would expect" the need to change the water
as once or twice a year. It might go several years.

73 and good luck,
Roger (K8RI)

On 4/23/2018 11:33 PM, Randy wrote:
On 4/23/2018 9:28 AM, wrote:
I know that really pure water is actually corrosive and will do it's
best to gain ions in order to get to some natural level of
minerals/contaminants.??? I built the coolers out of several pieces of
brass and hard silver brazed it all together.? I know the electrical
current will cause an etching or eroding effect of the materials in the
cooler, but I used what I had.?? At this point, I have no idea how often
I will changing? out the water.? Could be after only 10 hours of use, or
it may be 100 hours and the cooler may rot out in no time.

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