Wednesday, March 13, 2013

Addressing a Major Flaw in Water-maker Flushing . .

Last fall I repickled the water-maker in preparation for the winter.   While doing so I noticed the output was down a little. Part of that might be because it was late fall, and the water was colder.  But in Googling it seems the likely cause might also be some type of fouling in the RO membranes, either mineral or biological.  And given prior usage, Biological is most likely.   This is, after all, one of the key reasons one pickles the system when not in use.   Digging deeper turned up cleaning procedures (using Lye) and if possible warm water.  I will do this later this year.  But, there is a bit more here. . . .

Upon closer inspection I also noticed signs of bio-growth on the flow gauges    Just a little in the corners.  And the bottom of the production tubes had a bit of brown to them.  It got me thinking - the way we boaters 'pickle' our system is to circulate preservation through the membranes.  We even have two turn-outs to simplify this  (See Flush in and Flush Out in the diagram below) .  It is a very common to see this type of setup for small water-makers - heck some suppliers even sell special pre-filters that contain the needed chemicals to make it even simpler.

.But it got me thinking - this all-to-common procedure has a MAJOR lacking - it only treats the sea-water side of the system...   There is no way treatment will make it across the membrane into the produce side.  And I think that might be part of what has caused our reduced output - Bio fouling in the fresh water side.

So I made a simply modification to allow for treatment of the production side, ala:

Improved design with Fresh Water side Flush
Note also relocated heater-exchanger to pre-heat water
Note the addition of "FW - Flush In" and the two valves.  To use, I will connect the flushing pump up to "FW Flush-in" open the two small valves and place the "RO Water Out" hose back into the circulation bucket.  That way we pass treatment water through the whole fresh water side of the system.  Combine it with the Salt Water side flush and we will have a well treated system!

To make this change  removing the pressure tube end caps, drilling out the output hole (Or remove plugs, depending on your system), and installed the new valves and hose .

Original installation, note production side(hole in center of cap)  is not connected on this end of the pressure tubes.

And here is why, the hole is tapped, but not drilled through.

Careful to drill out

And add individual valves.
(Note the Lye-In-Waiting in the background!)

And the rest of the parts needed to complete a
"Fresh Water Flush"
As this is in the production side (fresh water side) pressure will be very low and plastic components can be used.  I added independent valves so I can  select each membrane for flushing and make sure both get a good dose.

With this change I can treat teat the Salt Water side, and then treat the Fresh Water side.   It seems an obvious lacking in most designs, and I am looking forward to cleaning the system this spring - both sides. And a  protection of ALL PARTS of the system when it is placed into storage next fall.

(And if you want to see more about Viking Star's Water-maker, click on the Watermaker link to the right)

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