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Old 14-03-2012, 12:15   #1
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When Your Bilge Pump Sinks Your Boat ... Experience

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, Catalina 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 and wind 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 off Catalina 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.

Cheers!
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Old 14-03-2012, 12:25   #2
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Re: when your bilge pump sinks your boat... experience

very interesting
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Old 14-03-2012, 12:27   #3
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Re: when your bilge pump sinks your boat... experience

Thanks for sharing that. That really will be helpful to others. Glad you had a floatable boat and it wasn't a lead bomb.
kind regards,
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Old 14-03-2012, 12:33   #4
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Re: when your bilge pump sinks your boat... experience

You should always check that the volume of water in the pump hose isn't enough to cause the pump to come back on after it drains back.
Better to have a small manually controlled pump in a small sump for getting that last bit of water out. With a larger pump in a more volumous location to handle "real" water problems.
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Old 14-03-2012, 12:50   #5
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Re: when your bilge pump sinks your boat... experience

Good reading, glad you didn't lose your boat. What type of tri do you have? Just courious, Have a great day..Michael..
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Old 14-03-2012, 12:54   #6
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Re: when your bilge pump sinks your boat... experience

I mounted my float switch on a small block raising it above the level of the pump for this reason, some designs of float switches have a small hysteresis for this reason.

Adding or changing bilge pumpage always takes a little tweaking to get it right. Thanks for the heads up.

PS another reason backflow preventers are a bad idea in bilge pump lines.
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Old 14-03-2012, 14:06   #7
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Re: when your bilge pump sinks your boat... experience

Check valves on bilge pumps cause more problems than they solve. That's why so many bilge pump manufacturers recommend against installing a check valve.

A few minutes from now someone will surely jump into this thread and write, "I've had a check valve on my boat for thirty years and it's never caused....."

But we've certainly seen previous threads where check valves have caused considerable harm.
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Old 14-03-2012, 14:30   #8
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Re: when your bilge pump sinks your boat... experience

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Originally Posted by Bash View Post
Check valves on bilge pumps cause more problems than they solve. That's why so many bilge pump manufacturers recommend against installing a check valve.

A few minutes from now someone will surely jump into this thread and write, "I've had a check valve on my boat for thirty years and it's never caused....."

But we've certainly seen previous threads where check valves have caused considerable harm.
---17 years couldn't resist Bash
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Old 14-03-2012, 14:37   #9
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Re: when your bilge pump sinks your boat... experience

Good warning. An airlock is another way a bilge pump can sink a boat

In my case this was a slight dip in the hose just before the discharge. The pump kept running but wasn't able to push water past the air lock.

I always now install two automatic bilge pumps. A small one on a tiny 1/2" hose for nuisance water and a larger one mounted about 3" higher in the bilge that should never turn on. No non-return valves.

Carl
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Old 14-03-2012, 15:22   #10
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Re: when your bilge pump sinks your boat... experience

Very easy trap to fall into. I had a similar experience with a shower sump pump. It would just keep cycling. Luckily I didn't have a check valve to mask the problem.

Glad your boat is alright!
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Old 18-03-2012, 09:44   #11
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Re: when your bilge pump sinks your boat... experience

A shower sump is the only place I would put a check valve, 1. It is less likely that debris from the shower sump will clog it. 2. A failure is unlikely to sink the boat. 3. It keeps the smelly water from coming back down.
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Old 18-03-2012, 11:15   #12
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Re: when your bilge pump sinks your boat... experience

The bilge pump delimma (how to trust your boat to it) and yet be aware when something major is happening with water ingress is a topic that is timeless. I think it ranks close to #1 for the most worried about problem for those that live away from their boats. I have seen it addressed a few different ways.
1. Close up every hole except the bilge pump outflow (above the waterline) prior to leaving the boat.
2. Having someone "check" the boat once a day for the waterline, and come in sit in the boat once a week to see how often the bllge pump goes off.
3. Have someone live on the boat while you are gone, or have a liveaboard at least a few feet away.
4. Set the bilge pump to it only goes off when it is above a certain level (usually about 2 gallons in the bilge), and then pump until it is completely dry, assuming about 1-2 pints of water of water will run back from the hose into the bilge. Design the outflow on the bilge with a loop high above the water and then going down to the outflow.
5. Have multiple bilge pumps.
6. There are some electronic gizmos that notify your cell phone when your pumps on constantly cycling. Have not tried them yet, but I may if my live-aboard decides to leave.
I use a combination of 3, 4, and 5- and I am sleeping better now than I have in the past.
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Old 18-03-2012, 11:22   #13
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Re: when your bilge pump sinks your boat... experience

Quote:
Originally Posted by Bash View Post
Check valves on bilge pumps cause more problems than they solve. That's why so many bilge pump manufacturers recommend against installing a check valve.

A few minutes from now someone will surely jump into this thread and write, "I've had a check valve on my boat for thirty years and it's never caused....."

But we've certainly seen previous threads where check valves have caused considerable harm.
Can you elaborate?
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Old 18-03-2012, 13:24   #14
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Re: when your bilge pump sinks your boat... experience

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Originally Posted by unbusted67 View Post
Can you elaborate?
Bilge Pump Situation

Bilge Pump Non-Return Valve

Challenge: Check Valves

Killed Batteries ?

Bilge Pump and Check Valves

Those are just the more recent ones. I'm sure there are dozens more. We had a thread one time where the fellow's boat ended up sinking because of his check valve. Many more that have experienced battery depletion because of this problem.

There are far better solutions to the problem people try to solve by using check valves.
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Old 18-03-2012, 13:30   #15
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Re: when your bilge pump sinks your boat... experience

Consider getting the Spot Hug- it will monitor your water in the bilge along with a host of other things and call you on the phone/e-mail for $150 a year
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