Spectra Watermakers Newport 400 - Manual (Page 44)

44
Operation and Repair Bulletins
The following documents are sections of our complete service bulletin set.
These are available on our website Spectrawatermakers.com
MB-2 MEMBRANE CARE
Membrane life is affected by a large number of factors and is somewhat unpredictable. A
big commercial plant running 24/7 will get 10 to 12 years out of a set of membranes. But
they do all kinds of fancy chemical injections and never shut the thing off. Most cruisers are
lucky to get five or six years out of one. You hear of the eight or ten year old membrane now
and then. The biggest killers of membranes are lack of use, chlorine damage, and improper
storage.
Don’t let membranes sit around with sea water or stale fresh water in them. Biological
growth will occur in the membrane. Here at the factory we frequently get back membranes
for inspection that reek of hydrogen sulfide (rotten eggs). This odor is produce by anaerobic
bacteria that live in an unused membrane, feeding on whatever animal or vegetable matter is
trapped in it from the plankton that gets through the system. Membranes badly fouled in
this way can seldom be saved. These bacteria are always present but are inhibited by the
oxygen in sea water while the unit is in frequent use, by scheduled fresh water flushes, or by
pickling. Keeping the prefilters clean is also important in preventing bio-fouling. If your
prefilters are allowed to become a breeding ground for bacteria (get smelly), the contamina-
tion will spread throughout the system. When we cut open a failed membrane we also find
mildew, another form of bio fouling, probably due to long term storage with no biocide or
stale biocide.
After many hours of water making mineral deposits will form and must be dissolved away
with an acid cleaner. Alkaline cleaners are used for bio-fouling. Cleaning chemicals, espe-
cially the alkaline, are not good for the membrane. Every time you clean the membrane it
shortens its life. Clean only when necessary, and avoid cleaning as a “diagnostic tool”.
Chlorine will destroy a membrane in minutes. It attacks the material that the membrane is
made from. Always use product water or water filtered slowly through a charcoal filter for
flushing and chemical treatments.
Oil simply plugs up the matrix of the membrane and clogs it up. We have brought back oil
fouled membranes with Joy soap (See MB-5 Cleaning with Detergent.)
For storage we recommend using propylene glycol potable water system antifreeze if avail-
able. It can safely be left in the system for one year and will keep things from freezing in
cold conditions. It is hard to find in warm climates, and takes up a lot of room on a small
boat, so our SC-1 is best for tropical cruising.
Given good care a membrane will eventually just start to slowly fade away. The feed pres-
sure may rise and/or the ppm go up. Hardly ever will they just fail overnight.
8/13/04