You've got me thinking about Tee fittings and watermakers. I keep pretty detailed notes and records about
maintenance on my boat and on other boats that I work on.
Apparently Spectra did not have the same degree of Tee concern in June 2000 because my Spectra 380c manual (revised 10/15/99) says "Sharing a thru-hull with another system is acceptable,..."
It does go on to say problems may result with flow restrictions and air bubbles but it does not require an independent thru-hull.
Another friend who installed a Spectra at the same time as I also used the engine
raw water thru-hull and has never had a problem. His original membrane only lasted 12 years. They cruised from
Seattle to Ft Lauderdale, and
Seattle to
Puerto Vallarta twice and on to
Hawaii once. They always had at least three and frequently five people on board and used the water maker every day for 10 years.
In 2002 - 2004 I worked closely with the Spectra representative (factory trained) in the
Sea of Cortez as we installed and repaired many Spectra systems. He never expressed any concern about the Tee off the diesel
raw water strainer. I don't
recall seeing any problems in the dozen or so boats I worked on with that arrangement.
Question:
a 2" thruhull can flow somewhere between 60 and 115 gpm (later estimate by Evans Stargazer) when two feet below the water surface. The 4JH2E Yanmar needs 16 GPM for cooling water (based on my factory
rebuild manual) and the Spectra needs a little over 3 GPM of feedwater so why is the tee a problem if there is at least three times that amount of water available?
The Yanmar impeller pulls less than 1/3 of the available water to it and the two Spectra feed pumps are below the waterline so water will flow, by gravity, to those feed pump intakes. The water that is not pulled to the Yanmar impeller will naturally flow downhill from the Groco to the feedwater pumps 3' below it.
What am I missing here?
I am not disputing the recommendations of the experts but I am wondering when this absolute prohibition on a watermaker sharing a through-hull with another system became the official Spectra policy.