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

John Lyles jtml at losalamos.com
Sat Apr 28 13:37:39 EDT 2018

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)" <k8ri at rogerhalstead.com>
> To: amps at contesting.com
> Subject: Re: [Amps] water purity/conductivity in water cooled, tube, >
> 	amplifiers
> 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, amps-request at contesting.com 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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