I thought that after what I just experienced I'd give a heads up to ANYONE using a bilge pump
on their boat... while it's a little embarassing to publicize this story I think if it helps someone else that it's worth it -
My boat 'Ceil' is a 1967 Hedley Nicholle Trimaran
. She is a 'cold molded' hull
with cedar strips diagonally laid with (now) fiberglass
and West Systems epoxy
. She is powered by a Yanmar
2Cyl and an SD 20 Saildrive
This boat was swamped once before I bought her 5 years ago - the boat was abandoned and the hatches left open - rain and fog
condensate filled her up (she couldn't sink as the amas held the weight of the main flooded hull). I completely refitted and reskinned her and added a Whale Super Sub Pump along with other systems to this boat.
As the bilge
was always dry, the pump never ever ran - well never ran 'until'...
(let's set the story up
I leave Ceil anchored in the great big ocean (GBO) outside Avalon
Isl (So Cal
, USA) all year. She is 'watched' by a local Capt who lives on his boat next to Ceil....
Anyway - after a trip to San Diego
last summer I found 1/8" of water
in the bilge
. I checked her carefully over a two week period but never found where the water
came from. There had been a severe storm (75mph gusts, 10ft seas ) the week before the leak so I assumed that wave action had somehow pushed water into the cockpit
and then under the outside engine
compartment cover to get into the bilge.
We dove the boat several times over the next three weeks and tried letting dye out around the hull
to find the leak and found that the SD 20 saildrive
was pulling a tiny bit of water in. I replaced the SD 20 water alarm
and indeed, after another week the SD20 started to complain of water between it's membrane. We were scheduled for a haul-out this April so I double-checked the bilge pump
(poured water into the bilge until it came to life) and after it had pumped out the bilge, figured we were safe until April.
My boat watch usually boards Ceil every week 'just-in-case' but was away for three weeks...
He called to tell me upon returning that Ceil had 18" of water (the bilge is ONLY 1" on this trimaran) in the main hull and had to have her pumped out. Most everything valuable was above this mark so it was more of a 'darn-it' moment that anything else.
But the event caused concern because the bilge pump had worked before sealing her up.
The bilge pump was a Whale super-sub pump with electronic switch (this means it does not have traditional float switch but an electronic sensor built-in to one end.).
The pump installation
directions were sparse at best but when we installed the pump we also installed a back-flow preventing valve (west marine
as well), I later found that the company recommended the valve...
Ceil has a solar
power and the pump was on a battery
bank that is directly charged by this bank. The fridge is also on this system. The fridge shuts down if the voltage gets below 11.5 vdc and does not restart until manually reset.
So the post mortem... in trying to figure out why the pump failed to pump out the boat we discovered an unusual behavior... the super-sub pump has a 'time-out' feature that shuts the pump off after the sensor fails to detect water over it for 15 seconds. If, after 15 seconds the pump senses water it will restart again.
In most cases this wouldn't matter but in our case, the tiny 'well' that we placed the pump into was a little (maybe 2 oz) less than the amount of water left in the evacuation tube leading to the above line bilge pump thru-hull.
The back-flow valve doesn't actually STOP water from flowing back down the hose it just slows it down a lot.
So - here's what happened - after we tested the pump, and for many cycles after that the pump worked ok. At some point the weather
degraded to a dead calm and little sun for several days. The pump would sense water and pump it out, the hose would remain full, the water would slowly at first but more quickly as the oxygenated water allowed critters to grow on the 'ball-valve' in the evac line leaked back more quickly.
The end result was that the pump started to shut-off then restart 15 seconds later repeatedly until with no sun, no wind
, and the fridge and anchor
lights helping, the battery
was pulled down below where the pump would / could run.
This is by any reasonable calc a 'one-in-a-million' event, but the result was the battery flattened out, the pump stopped pumping and the boat flooded. When the sun shined or wind blew it was enough to perhaps run the pump for a bit but not long enough to evacuate the main hull of all the water..
I'm not claiming that the pump was at fault as I set it and left, so the responsibility is mine (I'm glad the boat wasn't lost!!).
This got me wondering if there was some other way to use this pump - that wouldn't allow it to start the repeat cycle. In looking for a better solution than the check valve which isn't supposed to keep water from falling back forever...
I found some advice that the solution was to reduce the size of the evac hose so that if / when the water inside did seep back into the bilge it wouldn't be enough to restart the pump.
I inserted a smaller diameter hose into the standard hose and we tested this to see if it would work - and it has!
I also installed two other mechanical float switch controlled pumps on another battery just in case. We are still scheduled for haul-out in April.
The system has worked great to date - so the moral of this story is to check the volumn of your bilge evac lines to see if they are close to or above the volumn of water needed to start the pump working. If the hose is near the critical volumn, you need to either reduce it's diameter (if this is a safe option - I'm not proposing you do this unless you know the facts), or place the pump in a space where the 'backflow' won't be enough to trigger the switch.
In Ceil's case I relocated the pump a little higher up the wall of the hull.