Here's a non electronic way to skin the cat discussed in the "See
Water bilge switch report" thread.

In order to have a longer ON / OFF range than provided by common level
switches, put a standard float switch in a coffer dam of the height
you want to start the pump. Put one of those valves used in anti
siphon loops in the bottom. The bilge will fill until it overflows
the cofferdam and the float switch will turn on the pump. The
cofferdam will empty out through the one way valve with the bilge and
the float switch will go off.

This would also prevent surging water from burping the pump in a
seaway. You might need a pretty clean bilge to keep the valve from
plugging up. OTOH a screen across the top of the cofferdam would
probably keep things clean enough though. It would also protect the
float switch.

Damn. I like this idea! Much simpler wiring. With our large flat
bottom sump, I've got to build the cofferdam anyway to avoid the surge
problem. Saves forty bucks of additional float switches. What's not
to like?

The one way valve is the key thing. It has to let the water drain out
through 3 to 4 inch head but seal tight as the bilge fills. I just
bought a siphon break for our head. I'll fiddle with it and see if
these easily available and replaceable valves are the answer.

--

Roger Long

All this to avoid a check valve?

"Roger Long" wrote in message
...
Here's a non electronic way to skin the cat discussed in the "See Water
bilge switch report" thread.

In order to have a longer ON / OFF range than provided by common level
switches, put a standard float switch in a coffer dam of the height you
want to start the pump. Put one of those valves used in anti siphon loops
in the bottom. The bilge will fill until it overflows the cofferdam and
the float switch will turn on the pump. The cofferdam will empty out
through the one way valve with the bilge and the float switch will go off.

This would also prevent surging water from burping the pump in a seaway.
You might need a pretty clean bilge to keep the valve from plugging up.
OTOH a screen across the top of the cofferdam would probably keep things
clean enough though. It would also protect the float switch.

Damn. I like this idea! Much simpler wiring. With our large flat bottom
sump, I've got to build the cofferdam anyway to avoid the surge problem.
Saves forty bucks of additional float switches. What's not to like?

The one way valve is the key thing. It has to let the water drain out
through 3 to 4 inch head but seal tight as the bilge fills. I just bought
a siphon break for our head. I'll fiddle with it and see if these easily
available and replaceable valves are the answer.

--

Roger Long

Looks like it would work, if you don't mind a lot of water in the bilge.
Another solution to your long hose run/drain back is to have two pumps/float
switchs. Lower switch for small pump w/ very small hose. Then higher switch
w/ Mother of pumps.
This should protect the big pump fromwearing/rusting out 'til you really
need it.

"Roger Long" wrote in message
...
Here's a non electronic way to skin the cat discussed in the "See
Water bilge switch report" thread.

In order to have a longer ON / OFF range than provided by common level
switches, put a standard float switch in a coffer dam of the height
you want to start the pump. Put one of those valves used in anti
siphon loops in the bottom. The bilge will fill until it overflows
the cofferdam and the float switch will turn on the pump. The
cofferdam will empty out through the one way valve with the bilge and
the float switch will go off.

This would also prevent surging water from burping the pump in a
seaway. You might need a pretty clean bilge to keep the valve from
plugging up. OTOH a screen across the top of the cofferdam would
probably keep things clean enough though. It would also protect the
float switch.

Damn. I like this idea! Much simpler wiring. With our large flat
bottom sump, I've got to build the cofferdam anyway to avoid the surge
problem. Saves forty bucks of additional float switches. What's not
to like?

The one way valve is the key thing. It has to let the water drain out
through 3 to 4 inch head but seal tight as the bilge fills. I just
bought a siphon break for our head. I'll fiddle with it and see if
these easily available and replaceable valves are the answer.

--

Roger Long

"Doug Dotson" dougdotson@NOSPAMcablespeedNOSPAMcom wrote in message
...
All this to avoid a check valve?

Sure, mental exercise keeps you young.

You've had good luck with your check valve but others, including
myself in different applications, have not.

Do you strip your bilge out? With a hose full of water and the pump
and hose up to the check valve full of the trapped air, I don't see
how the pump could start pumping again. As long as you don't let the
water level fall below the check valve, it should be fine.

Of course, I'm now proposing a system with a check valve in it. But,
there is an even easier way. Just put a 1/2" PVC pipe siphon into the
cofferdam. It won't do anything as the water level rises. Once the
cofferdam fills, the siphon will keep the level in it the same as the
bilge and the cofferdam will empty as the bilge water is pumped out.

This is dead simple. Float switches should be protected from surge
and debris anyway.

BTW I actually like Garland's big pump - little pump solution but I'm
now committed by piping and purchase to the dual pump solution. For
other reasons, I want entirely separate and equal loads on each
battery.

Here's what the system would look like. Except for the 15 minutes
work to put in the siphon, it's pretty much what I would build around
the float switches anyway.

http://home.maine.rr.com/rlma/Siphon.jpg

It couldn't be much simpler.

--

Roger Long

With my dual keel stubs each (twin keel boat) and each segmented with
stiffeners into smaller compartments this seems much the better solution
than limber holes drilled everywhere. I'm looking for an easy to install
strainer on the sending side now. Something along the lines of the suspended
metal teabag brewing containers. Usually not much debris in those sections
but best to err on the safe side.


"Roger Long" wrote in message
...
"Doug Dotson" dougdotson@NOSPAMcablespeedNOSPAMcom wrote in message
...
All this to avoid a check valve?

Sure, mental exercise keeps you young.

You've had good luck with your check valve but others, including
myself in different applications, have not.

Do you strip your bilge out? With a hose full of water and the pump
and hose up to the check valve full of the trapped air, I don't see
how the pump could start pumping again. As long as you don't let the
water level fall below the check valve, it should be fine.

Of course, I'm now proposing a system with a check valve in it. But,
there is an even easier way. Just put a 1/2" PVC pipe siphon into the
cofferdam. It won't do anything as the water level rises. Once the
cofferdam fills, the siphon will keep the level in it the same as the
bilge and the cofferdam will empty as the bilge water is pumped out.

This is dead simple. Float switches should be protected from surge
and debris anyway.

BTW I actually like Garland's big pump - little pump solution but I'm
now committed by piping and purchase to the dual pump solution. For
other reasons, I want entirely separate and equal loads on each
battery.

Here's what the system would look like. Except for the 15 minutes
work to put in the siphon, it's pretty much what I would build around
the float switches anyway.

http://home.maine.rr.com/rlma/Siphon.jpg

It couldn't be much simpler.

--

Roger Long

Alas, like a lot of good ideas, the siphon doesn't work. I've just
mocked it up and experimented with it.

It would work in rapid flooding situation but, with slow water rise,
the cofferdam equalizes slowly with too much air left in the top of
the siphon to reverse the flow. If you could arrange the float switch
so that it didn't activate until the water was at the top of the
cofferdam, the siphon would start reliably. But, then you wouldn't
have accomplished anything.

This idea is only going to work with a good, reliable, low head, check
valve.

--

Roger Long