On eBay there's an ad for a 500 gpd watermaker (US Watermakers) that
uses a brass General pump.

Question to co - most watermakers seem to use either bronze, s/s or
titanium pumps - yours is brass. what's the expected pump life in
tropical (85-90 deg) seawater.

Answer from co - We have watermakers with brass pumps that have lasted
20 years. The damage that occurs to the pump is primarily when the
pump sits in salt water. The system should be back flushed after each
use with fresh water thus eliminating this problem. Most of the units
we manufacture have stainless steel pumps.

What about using the brass pumps - what he says is true WRT corrosion
- typical operations would be 1 hr per day and back flushed with RO'd
water. And brass should be fine in distilled water.

But what about plain old wear from hours of operation. What about the
pickling chemical?

What really wears out are the seals and that is the same regardless of
the cylinder and manifold material. A commercial brass head pressure
washer pump can last several thousand hours. 4 or 5 years of
watermaking time. He does have a point that, properly maintained,
backwashed and run every couple of days, the brass pump will probably
last for a good while. OTOH, if it soaks in sodium metabisulfite
pickling solution for long the cylinder walls have a good chance of
pitting. SMBS turns to sodium bisulfite in water which if it gets warm
can form a mild sulfuric acid.

Then again, a brass pump cost about half what a bronze pump does and one
quarter of a stainless pump. If it lasted more than a few years and you
could replace it yourself, it might work out dollar wise.

dg wrote:

On eBay there's an ad for a 500 gpd watermaker (US Watermakers) that
uses a brass General pump.

Question to co - most watermakers seem to use either bronze, s/s or
titanium pumps - yours is brass. what's the expected pump life in
tropical (85-90 deg) seawater.

Answer from co - We have watermakers with brass pumps that have lasted
20 years. The damage that occurs to the pump is primarily when the
pump sits in salt water. The system should be back flushed after each
use with fresh water thus eliminating this problem. Most of the units
we manufacture have stainless steel pumps.

What about using the brass pumps - what he says is true WRT corrosion
- typical operations would be 1 hr per day and back flushed with RO'd
water. And brass should be fine in distilled water.

But what about plain old wear from hours of operation. What about the
pickling chemical?



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

I asked Brent Swain the same question on the metaboatsociety.com forum,
and he replied that he has used a brass pump for 6 years with no adverse
affects,

see here http://tinyurl.com/29cbw

regards
garry



"dg" wrote in message
...
On eBay there's an ad for a 500 gpd watermaker (US Watermakers) that
uses a brass General pump.

Question to co - most watermakers seem to use either bronze, s/s or
titanium pumps - yours is brass. what's the expected pump life in
tropical (85-90 deg) seawater.

Answer from co - We have watermakers with brass pumps that have lasted
20 years. The damage that occurs to the pump is primarily when the
pump sits in salt water. The system should be back flushed after each
use with fresh water thus eliminating this problem. Most of the units
we manufacture have stainless steel pumps.

What about using the brass pumps - what he says is true WRT corrosion
- typical operations would be 1 hr per day and back flushed with RO'd
water. And brass should be fine in distilled water.

But what about plain old wear from hours of operation. What about the
pickling chemical?