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I have an Irwin 41 that I'm gradually figuring out, but my most recent finding is that the plumbing from my center cockpit drain goes down into a seacock/thru-hull fitting uneder the waterline at the bottom of my boat.

I don't quite understand this configuration. The cockpit sits high out of the water, so why not just have the drain lines go directly overboard out the stern, to an above-waterline egress? I could understand if I had a smaller boat with the cockpit floor close to waterline, as the heeling or alot of heavy weight in the back would make the boat more prone to take on water from the outside if the egress dips underwater, but having a thru-hull at the deepest part of the boat for a cockpit drain seems riskier.

Everything I read says to limit the amount of thru-hulls, and I am not understanding the practicality of this one.

In addition, even when my cockpit does drain water, not all of it will go out since the thru-hull is underwater, correct? So I'll have a certain amount of dirty-cabin standing water in my lines no mater what. I could see that maybe if I was underway, the movement across the bottom might suction this water out, but I'm docked right now.

Any comments are appreciated to help me undrestand this configuration. I would like to limit the amount of thru-hulls, and also have a cockpit that completely drains any water it takes on.

Thanks!
 

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Any water that goes down that tubing/hosing will empty and the remaining water in the hose be equal to the level of the 'ocean'. What will remain in the hose will be insignificant.
 

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Straight out-the-back cockpit drains, without below water through hulls would/do make most sense.

Taken to extremes, today's open cockpits are an extension of that idea.

Most boats, however, have issues with storage interference (lazarettes, propane lockers, steering systems, etc) that would conflict with such drains. in addition, those drains are often relatively flat and can become dirt collectors and breeding grounds for algaes themselves.

We once converted a 'down through the hull' cockpit drains to an out-the back on a former boat.. we went out under the counter, but above the WL. Turned out the sternwave underway, esp when heeled was higher than the cockpit floor aft, and we created a cockpit backflooding issue that hadn't been there when the cockpit drained straight down and through at the front.

So... like so many scenarios.. 'it depends'. ;)
 
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That is a strange way to configure cockpit drains. My Cape Dory 25D was set up like that, too and it only had a manual bilge pump, so I always closed them off when I left, which always resulted in standing water in the cockpit after a rain. But, I figured that was better than than finding nothing but the mast poking up out of the water one day. :)
 

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Mermaid Hunter
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I have an Irwin 41 that I'm gradually figuring out, but my most recent finding is that the plumbing from my center cockpit drain goes down into a seacock/thru-hull fitting uneder the waterline at the bottom of my boat.
On center cockpit walkovers you can run the cockpit drains athwartships. That doesn't work with a walk through. You can't go through the transom without hoses at knee level or higher between the engine room and the berth.

The vertical drains on my center cockpit boat have yet to be an issue.
 

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That Drunk Guy
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My H.R. Monsun not only has the cockpit drains going to through hulls straight down below the waterline, but the deck drains also go into the boat and connect to these lines. I heard somewhere (can't remember where) that it is purely cosmetic so that you don't have residual slime and goo running down the outside of the hull. I am NOT a fan of the deck drains going through the boat at all...but what the hell do I know?
 

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Bristol 45.5 - AiniA
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We have cockpit and deck drains going straight down on our centre cockpit Bristol. Perhaps it was the way things were done in the good old days, I am not sure. I do know that I have an incredible number of thruhulls to worry about.
 

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Courtney the Dancer
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Our cockpit scuppers exit below waterline and the hoses cross over to the opposite side so that when heeled over the scupper isn't below waterline. I've done the measurements to try and run them out the transom (to eliminate two through hulls) but like Ron we would have water in the cockpit at about 15-20 degrees of heel. I guess I just have to live with them. We did eliminate the deck scuppers that also had through hulls by glassing them over and cutting three oval holes through the side of the hull.
 

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They work fine but unclogging drains like that can be royal PITA.
 

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I've wondered about that too.

On the new model Catalina 22 the cockpit sole slopes towards the back and and the cockpit drains are just holes through the transom.

My older boat has cockpit drains right in front of the companionway that go straight down to a thru-hull in the bottom of the boat. The cockpit sole slopes down towards the front so water runs toward these drains.

It seems like that adds unnecessary complexity and expense, so I wonder why they did it that way. Tradition?
 

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My through hulls exit through the hull behind the water line but ahead of the transom. Under way they are likely under water but at the dock they are a couple of inches above it so no worries.
 

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Judging from my own transom, I'm going to concur with an earlier poster that the underwater drains are to keep unsightly streaks and stains from developing.
 

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islander bahama 24
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That is a strange way to configure cockpit drains. My Cape Dory 25D was set up like that, too and it only had a manual bilge pump, so I always closed them off when I left, which always resulted in standing water in the cockpit after a rain. But, I figured that was better than than finding nothing but the mast poking up out of the water one day. :)
That's not really a good idea to close the cockpit drain off saw a boat full of rain water filled the cockpit and spilled over into the cabin wasn't a pretty sight to walk up to also with proper maintance the possibility of a drain line failing is minimal
 

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Guys my clipper marine 21 has the single drain and biggest problem is if leaves block it and then you can have a bathtub! :laugher System works guess I need some sort of strainer.

Dan
 

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Same boat Same settings
Several bad experience
First a clamp failed underway ...lots of water incoming !
Second There is a fair amount of water that stays in the pipes and hoses
And mine froze at the dock during winter Hose burst open with seacock open
Again lots of water incoming and boat started to list on its side with about 2 feet of seawater inside

So I changed the setting Cockpit drains are going directy into bilge and seacock is permanently closed
This winter I plan to have the drain evacuate directly at the stern above exhaust with a back valve as security Very easy to do on the Irwin 41
 

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Our 1975 B24 has cockpit drains that go straight down thru the hull with no seacocks. The boat was designed this way, we have had the boat going on three years with no issues, and hopefully never will. :)
 

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That's not really a good idea to close the cockpit drain off saw a boat full of rain water filled the cockpit and spilled over into the cabin wasn't a pretty sight to walk up to also with proper maintance the possibility of a drain line failing is minimal
Well, I only lived a couple of blocks from that boat and checked it on the way to work almost every day. I probably wouldn't do it if I lived where it wasn't convenient to check it every day.

According to Boat US, most boats sink at the slip, and most of the time it's due to an open thru hull, and slipped or burst hose. Everything on that Cape Dory was first class. I just don't know why they rigged the drains that way. Probably as someone else suggested, so there wouldn't be water stains on the hull from and above the water line drain.
 

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My 1966 Tartan 27 has two drains that go straight to the bottom, exiting through thru hulls. I replaced the hoses, double clamp them, and forget them. Luckily, in an emergency, they are easily accessible.

SKywalker
 

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With the cockpit drains below water level, while the boat is moving a partial vacuum is created and the water is sucked out of the cockpit faster than if it had a static drain. this is the Venturi effect. Myself I like a dry cockpit.....
 

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I have to big cockpit drains that go straight aft on the 47.7. If we were to get swamped, most of the water would exit there. But the big wheel is recessed into a well that has a drain straight down through the boat to a below the waterline through hull. This ends up being the main drain, as the water in the cockpit never makes it aft of this well. And, it tends to get clogged often.
 
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