"Dazed and Confuzed" writes:

If you can be so sure that there are never going to be any leaks....

I kept my boat on a mooring unattended from Monday thru Thursday, 6 months
out of the year without any problems.

conductivity.

Conductivity is the lowest cost and most unreliable of all the electronic
level measuring technologies. Too many problems with build up on the probes
over time.

So put your sensor in a small tube open at the top and with small holes at
the
bottom. this will be at whatever the bilge level is, but will more or less
isolate the sensor from sloshing.

AKA: "Stilling well" an old and out of date technology abandoned as too
labor intensive to maintain by the waste water industry at least 20 years
ago.

You may be right.

I know I am. 20+ years in the business tells me that.

So what is the method of your $500 solution?

There are a couple of technologies that have a chance.

You could use a capacitance probe that ignores probe build up.

My choice would probably be a vibrating tuning fork. By its very nature, it
ignores probe build up.

Either one of these units would include a build in time delay set for maybe
30 seconds.

The pump would energize after a time delay when the liquid contacts the
probe.

The time delay helps to eliminate splash or sloshing false starts.

When the liquid falls below the contact point, the 30 second time delay
would keep the pump running for 30 seconds.

The alternate to time delays is a 2nd probe.

SFWIW, we provide a 100% money back performance guarantee for every unit we
sell.

We definitely would not be willing to provide that guarantee for this
application.

Maybe this gives you a little better perspective why I consider level
switches in the bilge of a boat a waste of time and money.


--
Lew

S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland)
Visit: http://home.earthlink.net/~lewhodgett for Pictures