The JCCs once had a lecture by a sewage engineer describing anecdotes from
his many years of experience. One comment he made which was later
reinforced by my father's comments is that, for low pressure flow, a "hump"
in the line can entrap an air bubble which will block the flow
significantly.

Dad was describing the miseries of covering for those rotten architects that
decided to save money on a high-rise by reducing the pitch of the floors.
Without enough equipment space above the ceiling, the various plumbing and
electrical runs and (his concern) the HVAC ducts had to have all manner of
humps and dips to cross each other and these could lead to for both
installation and maintenance. The Marina Towers in Chicago had a
ventilation blower with a 4' wide filter and only 3' beside it in the
equipment room. To change it required folding and contortions. Kroschell
Engineering (his firm) was called in to make the system work after the
initial, low bidder, was thrown off the job. The drain pipes were a
particular concern because humps like those mentioned above were forbidden.

So maybe your 3" hose looks like a 1" hose if you don't run it well.
Entrained air will form a bubble.

Roger

http://home.insightbb.com/~derbyrm

"Matt Colie" wrote in message
...
Glenn,

I have always been amused by instructions like those you reference. The
notes usually make it sound as though nothing in the route could be above
the expansion tank (deaereator). - Nice Trick

I'm going to assume you want to know what matters.

The manufacturer is afraid that the disharge from engine may no be able to
push "over the hill".

Just do your best to avoid Big High loops in the routing. The jacket
water pump is capable of pretty good discharge head, and that only really
matters until the cooling system is full. An air bubble would have to be
really something to prevent the jacket water from flowing all the way
through the loop. Lots of the cars built everywhere can't be completely
filled from the pressure cap.

If you have to go up a foot from the engine connections, no big Whup. Just
be sure to bleed the hoses at start up and keep a eye at the deaereator
level for the first few hours.

Good Luck Guy - I've been watching.

Matt Colie

Glenn Ashmore wrote:

OK. The Yanmar 4JH4 is on the stringers, exhaust run to the waterlock
and raw water hose is on the strainer. Now I turned my attention to
running hoses to the water heater at the back of the engine compartment.
The instructions suggest that to avoid air traps the hoses to the heater
should be run below the level of the engine heat exchanger. BUT the
inlet and outlet for the water heater feed is on top of the pump which is
at the top front of the engine!