I recently discovered a sump in the very lowest part of Sanderling's
bilge. The "pit" is approximately 4"w X 6"L X 10" deep (less than a
gallon of water). If I could figure out a way to move the small volume
of water out of the pit when it fills, the remainder of the bilge would
be dry (eliminating odors and cleaning issues). I currently have a hand
operated diaphragm pump built into the bulkhead at the lower steering
station pumping the pit, but it is way too inconvenient to keep the pit
dry using that method.

Because the cross-section of the pit is so small, a standard float
switch connected to a pump wouldn't move enough water to even fill the
exit hose to the thru-hull, so I'm trying to devise a switch that would
have an upper and lower limit - when the water level reaches the top of
the pit the switch would activate (close), and when the water level is
near empty the switch would de-activate (open). Obviously, the switch
(and pump) needs to work on 12 volts.

My limited experience with household sump pumps goes back a few years,
but one method household units use for switching is a float attached to
a rod with an upper and lower limiter and a mechanical switch that is
thrown by the limiters. The key to coming up with such a system seems to
be the mechanical switch, and that is where I'm currently stuck.

An alternative would be to build some sort of "field effect" device that
would have upper and lower limits that would trigger a solenoid and
thence the pump.

I realize I may have to use a check valve in the discharge line because
of the small volume of water being pumped out at any one time.

Any ideas?

FWIW, this would not be the "keep the boat from flooding" sump pump.
There are two large pumps set up in the conventional manner that would
activate sequentially in the event of the "pit boss" failure.

--
<><><><><><><><><><><><>Mozilla Thunderbird<><><><><><><><><><>
Bob McLeran and Judy Young              Manatee Cove Marina
MV Sanderling                            Patrick Air Force Base
DeFever 41 Trawler                      Melbourne, Florida
Blog: http://sanderlingcruise2010.blogspot.com/
Pics: http://tinyurl.com/yjx2vky&  http://tinyurl.com/yhxjvas

Bob,

Check out http://wemausa.com/http://wemausa.com/.  They make tank level
sensors similar to what you are looking for.  I worked with them many years
ago and found them helpful for a custom setup I needed.  Maybe they can help
you with your problem.

Ron Nelson
Port Orchard, WA

How about the Arid Bilge system? http://aridbilge.com/Home_Page.html

Keith

-----Original Message-----
From: trawlers-and-trawlering-bounces@lists.samurai.com
[mailto:trawlers-and-trawlering-bounces@lists.samurai.com] On Behalf Of Bob
McLeran

I recently discovered a sump in the very lowest part of Sanderling's
bilge. The "pit" is approximately 4"w X 6"L X 10" deep (less than a gallon
of water). If I could figure out a way to move the small volume of water out
of the pit when it fills, the remainder of the bilge would be dry
(eliminating odors and cleaning issues). I currently have a hand operated
diaphragm pump built into the bulkhead at the lower steering station pumping
the pit, but it is way too inconvenient to keep the pit dry using that
method.

Bob, let us know when you come up with an idea for a switch, I'd like to hear about it.

But one thought comes to mind about your situation, at least as I understand it, - even if you get a switch to do what you want, will the set up be able to remove enough water, even with a check valve installed, to make it worthwhile?

Here is a thought that may or may not work in your situation. Most bilge pumps, for a variety of reasons, cannot pump clear to the bottom of a bilge or sump and will leave a considerable amount of water, even if back flow was stopped with a check valve.

What we did on our boat is to orient the suction hose that goes to a remote mounted pump (manual, of course), to sit vertically, with the hole in its end within a fraction of an inch from the surface of the bottom of the bilge.

When Jill finishes pumping (once a year or so) this still leaves a little water in the bilge, and does not stop back flow, which a check valve might be useful for, but it does empty more water than if the hose was orientated horizontally, especially if a strum box was fitted or a regular bilge pump was installed.

The back flow in our situation is minimized by using a diaphram pump with flapper valves, so very little water remains in the hose when finished anyways.

To make it even more effective, you could narrow in the sides of the sump to the point that, when they meet the bottom, just enough room for the hose was left. (Think of all the fun your wife would have doing the glass work!)

I'm also curious to why you would want to try and keep this area dry to begin with? I'd doubt that a little standing water is a serious problem unless this water was splashing into things better kept dry.

If osmosis is the consideration, then instead, consider drying out and coating the sump. This might be a better option as no matter how empty you make it, either some water will remain, return, or will start to gather again, probably keeping this area wet anyways. If you waterproof the sump's surfaces, then a typical bilge pump system, whether an "on-site" pump or a remote pump, might satisfy your needs since the possibility of osmosis was eliminated a some standing water wouldn't do any harm??

Just idle curiosity coupled with mental gymnastics; after all, this is the guy who suggested having one spare prop for a twin engine boat! By the way, kudos to Marin for coming up with a way to justify only having one spare prop on a twin engine boat!

Rudy
Briney Bug, Panama City, Fl

Sorry, I started out with this thought and got so side tracked that I forgot to mention it... maybe a timer hooked up to an electric pump instead of a switch?

Rudy
Briney Bug, Panama City, Fl

A foot valve would be best. Whale makes a strainer which fits flat and has a
built-in check valve. This arrangement is known as a foot valve and will
give you the driest bilge owing to the location of the check valve.

Ron Rogers

...and for a completely different approach...
Given that the area is difficult to access, that a very small amount of
water is involved,
and that control of odor is the issue as well as the 'feel-good' that your
bilge is dry....

Simply add a fan which moves air from higher in the engine room (hotter)
across the area in question (cooler),
evaporation will completely fix the problem. If the fan is wired through the
start key,
then the air movement will only be during engine operation and odors will be
eaten by the engine
with the bonus that the marginally cooler air improves combustion
efficiency. Leave in place the
existing system in case high volumes of water are experienced. This has the
benefit of not requiring
operator attention, fail safe, redundant, no risk on existing power needs,
and working to the last drip.

Richard Tomkinson