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.
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.