Is the 1" pvc pipe part of the vent/overlow for the tank? Many boats
have their vents inboard. I have a siphon start where the end of the
vent line is below the top of the tank, and the fill on the tank is
above the vent location (tank not level, boat heeled, boat not trimmed,
etc). If this is the cause, the siphon should only start when the tank
is filled, and should stop when the water level drops below the vent
location on the tank...

bob

Joe Bleau inscribed:
In my many years of building and sailing boats this is one of the most
perplexing problems I have ever encountered.

1. I have shut off the water at the tank itself. There is a shut off
valve on a 3/4" pipe only 2 inches from the tank itself. Thus I am
pretty certain the problem is not downstream from the tank.

2. The Morgan OI has another, smaller tank, in the engine room. I
have also cut off the water at that tank.

3. In the engine room, just below the engine, the hull configuration
creates a sump where one of my bilge pumps is located. After I had
all tanks turned off I noted that my bilge pump kept cycling on and
off. Tried to find the source of this anomaly. Could not see a
thing. Got a 10"x10" acrylic mirror. Slid the mirror down into that
area and observed a steady stream of water coming out of the open end
of a 1" PVC pipe which had been glassed onto the bulkhead just below
the engine. Since all tanks were shut off and since no more water
would come out of the faucets I knew that it could not be a leak in
the plumbing system, not only because the tanks were shut off but
because the steady stream continued long after time had elapsed for
all the pipes to drain. Let it run for an hour and a half. I then
plugged the pipe, assuming that the 1" pipe might be a drain pipe
leading from the port water tank (sort of like the drain pans used on
domestic hot-water heaters). I reasoned that if that were indeed the
source then, with the pipe plugged, it would back upl and the water
would then begin to leak from around the bottom of the tank.

Left it overnight. Still no dampness anywhere. What, in the name of
the Good Lord, could be the source of that steady stream of water.
What a mystery. In the absence of a genius in this group telling me
where it is coming from I am about ready to attirbute it to some yet
unknown Water God.

Another curious thing is what in the world was the purpose of that
pipe which was clearly installed when the boat was built. Maybe I
will try to track down Charlie Morgan and ask him. Fat chance he will
remember after these many years and all the different boats he built.

I think I will now try Salnick's suggestion of filling the tank to the
brim and measuring it daily. I simply do not know what else to do
short of going ahead and removing what I can't help but believe is a
sound tank.

Thanks to each of you who was generous enough to reply.




On Wed, 24 Jan 2007 11:46:50 -0800, RW Salnick
wrote:



What does "I could not get pressure" mean? Making the assumption that
this means that you could not pressurize your faucets, I assume that you
checked out your fresh water pressure pump and found it to be in good
condition. And that you checked out the line from the tank to the pump
and ascertained that it was not leaking air into the pump. And that
there is no leak downstream of the pump which is simply dumping water
into the bilge as fast as you can put it into the system with the pump.

Right?

Pressurizing with compressed air would be very dangerous. With as
little as 10 psi, it could explode. Another poster suggested only
pressurizing enough to inflate a balloon - this would be safe, but it
might be too sensitive - you will have made a barometer!

Can you just fill up the tank to the top, and then check it a few days
later (without using any water!) and see if the level has changed?

bob
s/v Eolian
Seattle