After a long break, back to usenet.

Have you ever been told something by an "expert", but you're not sure
if what they say is right? The thoughts of my peers would be
appreciated.

About to do a bit of plumbing on "Hinewai" and was chatting over a
beer to the chap who does loads of plumbing work on the boats in our
marina. He charges like a wounded bull, hence the chat over a beer
and doing it myself.

We've just cut a new through-hull which feeds a three way manifold.

Manifold Exit 1 will go to a sea water foot pump for the sink - the
tap will be not that far above waterline. Sink empys into a grey
water sump tank (below waterline) which is then pumped overboard via a
high loop, joining the exhaust out pipe just before it comes out
though the transom. The loop in the lazerette is unvented since it's
not connected to any below waterline water-in thingy.

Manifold Exit 2 will go to the heat exchange pump on the new Isotherm
Refrigeration

Manifold Exit 3 will go to the watermaker.

The thru hul is, of course, valved - each manifold outlet will have a
manual valve.

Once the water's done its stuff with the fridge and watermaker, the
waste pipes will both link, below waterline, into grey water out
system on the output side of the sump tank and pump - back flow will
be stopped by either a non-return or/and a manual valve. The pumps
for both fridge and watermaker have enough balls to get the waste past
the loop in the lazerette.

My plan was to put vented loops on:

1. The output side of the foot pump

2. The output side of fridge pump

3. The output side of the boost pump to the watermaker serious pump.

Then, at least, should we lose any pipe work on the output side of the
(below waterline) pumps, we wouldn't sink. I can't see any time
manifold outlets 1 & 3 would be open when we are not aboard, but we
might be sleeping. There will certainly be times I can see that the
fridge will be running when we're on-shore.

My question to "the plumber' was whether I should consider a vented
loop on the output side of the main watermaker pump - not in the high
pressure bit, but in the brine waste. While the O tubes are above
waterline, the output pipe dips below waterline to marry into the grey
water output.

His advice was not to bother with vented loops for the sink and
watermaker if we'd be there when those valves are open. In some ways
that makes sense (but.. zzzzz), but I was blown away when he said I
didn't need any vented loops at all with any of these pipeworks as
long as I double clipped all joints and put a vent on the lazerette
loop. He's seen the planned set up when he quoted me for the job, but
that seems like a crock of sh*t to me.

I'd welcome your thoughts (although still mean to put vented loops in
as planned). Any thought's on the brine side of the watermaker? I
must admit I can't see any need to vent the loop in the lazerette, but
maybe I'm totally confused over this whole issue.

Thanks

Peter

Ocean Odyssey
Australia
www.oceanodyssey.net

"Do not measure your life by the number of breaths you take,
Rather by the number of times life just takes your breath away"

If you do decide to put in vented loops, here are some DIY valves that
have worked for me for 14 years now with zero maintenance.
Instructions at http://www.yandina.com/hints.htm#Siphon

On Wed, 18 Oct 2006 20:10:40 +1000, Hinewai wrote:

His advice was not to bother with vented loops for the sink and
watermaker if we'd be there when those valves are open. In some ways
that makes sense (but.. zzzzz), but I was blown away when he said I
didn't need any vented loops at all with any of these pipeworks as
long as I double clipped all joints and put a vent on the lazerette
loop. He's seen the planned set up when he quoted me for the job, but
that seems like a crock of sh*t to me.

I'd welcome your thoughts (although still mean to put vented loops in
as planned). Any thought's on the brine side of the watermaker? I
must admit I can't see any need to vent the loop in the lazerette, but
maybe I'm totally confused over this whole issue.

I'm not as sure that what I'm doing is right as I was before I read
your message. I have vented loops where siphoning can either damage
something or will result in water flow into something that is open to
the interior of the boat. Vented loops are on the engine and genset
exhaust lines for the first reason. They are on the head feed and
pumpout lines and a washing machine drain for the second reason.

I didn't put them on the brine discharge line or the aircon and
refrigerator cooling water overboards because these are closed systems
that are used to having salt water in them.

There aren't any on the sink drains and I make a point of closing
those throuhhulls when under way. I guess there is some risk of
sinking at the dock if a drain line were to fall apart.

Incidentally, if your refrigerator vents above the waterline, be
careful about your watermaker pump sucking air through the
refrigerator's water line. My existing watermaker shares an inlet
through hull with an airconditioner and I have shutoff valves on each
line to reduce the possibility of sucking air. I still have some air
bubbles in the water maker water that I haven't found the source of.
That causes havoc to the membranes.

The new one is going to get its own throughhull. It's installation
manual says sharing a throughhull will void the warranty....for what
that's worth.