On Thu, 29 Jan 2009 16:24:55 -0800, John Navas
wrote:

On Wed, 28 Jan 2009 18:27:21 +0700, BruceinBangkok
wrote in
:

On Tue, 27 Jan 2009 19:28:28 -0800 (PST), Peter
wrote:

Run a clear plastic hose (the one with the string embedded in the
tubing wall) from the drain of the tank to the water tank vent. You
then have a site guage for the tank. If you are a sailboat you may
have to run the line across the boat so when it heels you don't drain
the tank.

You don't even need then vent connection, just run the tubing a couple
of feet higher then the tank so it won't run over when the boat heels.

Surge siphoning can still be a problem. I speak from painful
experience.

I can understand surge but siphoning when the outlet is above the
inlet?
Cheers,

Bruce

On Fri, 30 Jan 2009 19:23:29 +0700, BruceinBangkok
wrote in
:

On Thu, 29 Jan 2009 16:24:55 -0800, John Navas
wrote:

On Wed, 28 Jan 2009 18:27:21 +0700, BruceinBangkok
wrote in
:

On Tue, 27 Jan 2009 19:28:28 -0800 (PST), Peter
wrote:

Run a clear plastic hose (the one with the string embedded in the
tubing wall) from the drain of the tank to the water tank vent. You
then have a site guage for the tank. If you are a sailboat you may
have to run the line across the boat so when it heels you don't drain
the tank.

You don't even need then vent connection, just run the tubing a couple
of feet higher then the tank so it won't run over when the boat heels.

Surge siphoning can still be a problem. I speak from painful
experience.

I can understand surge but siphoning when the outlet is above the
inlet?

While it won't continue indefinitely, momentum of water in the tube from
surge movement can draw additional water out due to siphoning until that
momentum is lost, resulting in quite a bit more outflow than expected,
which can have additional negative consequences when the vent outlet is
near things that can be damaged by water. Thus the vent outlet should
be high enough to prevent outflow even when heeled over, including surge
effects, and even so should drain overboard or at least into the bilge.

--
Best regards,
John Navas, publisher of Navas' Sailing & Racing in
the San Francisco Bay Area http://sail.navas.us/