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Old 12-05-2015, 20:23   #1
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Don't want to sink.

What is the proper operating procedure regarding raw water thru hull valve and for the head. They are a real pita to get too on Escaped from New York. I know to close the raw water cooling valve if the diesel doesn't lite off right away, but under what circumstances can a boat sink at the dock (ignoring a hose failure) by leaving the head and engine thru hulls open. I recall reading about a sinking from a head thru hull but can't recall the details. Is there an evil siphon fairy at work here?
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Old 13-05-2015, 05:21   #2
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Re: Don't want to sink.

there should be an anti siphon in the line
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Old 13-05-2015, 06:11   #3
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Re: Don't want to sink.

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Originally Posted by sailorboy1 View Post
there should be an anti siphon in the line

And it should be between the bowl and the pump, well above the waterline. Unless your head is above the waterline as ours is. Then this isn't needed.


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Old 13-05-2015, 08:32   #4
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Re: Don't want to sink.

Thanks for the replies. This is my first boat with a real head, so it's a new plumbing system to me.
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Old 13-05-2015, 10:22   #5
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Re: Don't want to sink.

The raw water intake through hull is plumbed directly to the head pump. There is no loop or anti siphon valve on the pump intake side (otherwise the pump wouldn't work). The pump itself contains check valves and seals that prevent flow from the intake through hull to the head. Many head pumps have a "dry" setting that closes a valve on the intake side. However, if valves fail open, seals fail and/or someone left the pump on "wet", and sea level is above the head rim (consider heeling on that side) water can flow into the head and over the rim into the boat, possibly leading to sinking. The discharge side should contain a loop elevated well above sea level (remember heeling) with an anti-siphon valve at the top to prevent flow from the outlet through hull back into the head. All this stuff including the hoses can fail so in my opinion it is wise to close both through hulls whenever the boat is left unattended.
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Old 13-05-2015, 10:31   #6
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Re: Don't want to sink.

I'm not disagreeing with the above advice but can tell you that my Dana is not plumbed this way. There is a valve for inlet water located right next to the head and before the pump. Instructions are "open valve, use head, close valve when done". No anti-syphon vent on the water intake side. This may not be the safest system- just saying some boats are done this way. I close the main through-hull when I'm away from the boat.
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Old 13-05-2015, 10:40   #7
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Re: Don't want to sink.

All good comments above. Key question is whether your head sits anywhere near the waterline, below or well above.
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Old 13-05-2015, 12:53   #8
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Re: Don't want to sink.

I haven't seen where anyone mentioned the obvious - make sure your bilge pumps and float switches (redundant) are in good working order. I keep my head valves (both) closed when the boat is sitting. I never close the raw water intake for fear of forgetting to open when I crank the engine. I sail twice a week all year round.

If you are in a marina and have Wifi, you can go to your nearest Lowes and purchase a $179 IRIS system that will text and call you if it senses water. You can add a camera to the system for another $100 and take a peek whenever you want from your Iphone.

There is a wealth of information on the internet on how to plumb a a toilet with an anti-siphon loop.

Good luck!
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Old 13-05-2015, 14:32   #9
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Re: Don't want to sink.

My view is that you should simply make it a discipline to always close all seacocks when you leave the boat....I am somewhat paranoid about this. Our marina has had 3 boats sink at the marina in the last year. The causes are not all clear, but two of the 3 boats were in very good condition.

It is also good to give the valves regular exercise to stop them seizing.
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Old 13-05-2015, 14:37   #10
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Re: Don't want to sink.

Any fitting below the water line can come lose and sink your boat. Having contorted my arm into a number of places my eyes couldn't follow it...I'd say to consider wasting a day or weekend making the valves friendlier. That could mean a thorough cleanup and some fresh paint under the sink to brighten the compartment. Or adding in a light, so you can see back there. Or just lubing the valves so they move easily. Possibly replacing them if they're 40 years old and crotchety. Or maybe getting a "pickle fork" or having one welded up from inexpensive rod stock, so you can stick the "fork" in between the plumbing and reach the valve without having to contort your body to see and reach it.


Usually worth the effort to fix it and be done with it. Especially, if there's old parts that you can't rely on anyway.
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Old 14-05-2015, 20:03   #11
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Re: Don't want to sink.

Thanks to all for the information. Update as follows:

Had the thru hulls and old hoses replaced and double clamped at last haul out.

Found the vacuum breaker for the head and the valve was clogged and in upside down (duck bill up instead of down). Cleaned and reinstalled correctly.

Have decided to close all thru hulls when at dock. Belts and suspenders.

Will just have to get in the habit of remembering to open raw water valve when starting the diesel.
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Old 14-05-2015, 20:12   #12
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Re: Don't want to sink.

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Originally Posted by mserafi1 View Post
Will just have to get in the habit of remembering to open raw water valve when starting the diesel.
Good way to do this is to tag the key or ignition IE put a label on it reminding you the seacock is closed. That way if you aren't there and someone cranks the engine they will also the reminder.

I know some boaters that hang the key on the seacock handle.
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Old 14-05-2015, 20:29   #13
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Re: Don't want to sink.

"Will just have to get in the habit of remembering to open raw water valve when starting the diesel. "
Easy. Got a key? Go to a local pilot shop and buy one of those big red ribbons that say "REMOVE BEFORE FLIGHT". Put the key on it, and hang it on the water intake valve, not in your pocket, when you shut down the boat.


Don't worry about theft, boat keys are pretty much an illusion anyway.
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Old 14-05-2015, 21:25   #14
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Re: Don't want to sink.

I second the "Hang the ignition key on the raw water valve handle".
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Old 15-05-2015, 14:53   #15
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Re: Don't want to sink.

Works for me.....or a tag on the key that says "open the rw seacock dumbass".

Also, do you all have a vacuum breaker on your raw water line? My Yanmar 2GM20F doesn't.

Thanks
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