How to vent a cabin-mounted day tank on a Catalina 30?

Nov 15, 2015
268
J J/30 Seward, AK
Hello!

I am trying to figure out how to vent a diesel day tank for my new diesel cabin heater. The tank is mounted inside the on a bulkhead on the beam of this Catalina 30 (see attached photo) and will be filled via transfer pump from the main tank. I am not familiar with thru-deck hardware, spillage concerns when heeling over, etc. I can only imagine that venting to the cabin will make the cabin smell like diesel.

I know that the water tank vent goes through the deck up into a stanchion which has a hole drilled into the side. Seems like running a tee into that vent potentially exposes the water tank to diesel overflow. There is another stanchion next to the spot where I want to mount the tank - should I drill a hole and vent the tank there? Or should I run the vent along the top of the cabin all the way back to the main diesel tank vent on the transom? Or is there some vent I device can buy that I can install right through the deck that won't let water in?

Concerning heel: I am surprised that sea water does not enter my fresh water vent mounted into the stanchion at full heel.

What considerations I should make for venting a day tank?

Thanks!
-Patrick
 

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Oct 24, 2010
2,405
Hunter 30 Everett, WA
No experience here, but I'd assume it vents like an engine fuel tank.
Ken
 
Jan 5, 2017
2,263
Beneteau First 38 Lyall Harbour Saturna Island
I had the same tank on my E-28+ but in the cockpit locker. Just used a high loop out of poly line for a vent. Never any problem unless I didn't pay attention when filling it. ( I didn't have my settee cushions right under the tank fortunately)
 
Jan 5, 2017
2,263
Beneteau First 38 Lyall Harbour Saturna Island
How do you plan on plumbing that? You'll need a long fuel line from your main tank then a shorty to the heater.
I think I would put the day tank in a stern locker and run the fuel line in the bilge, up inside the locker ahead of the heater and through a small hole in the bulkhead to the heater metering device. I know that takes away from storage but you don't have to live with it inside.
 
Nov 15, 2015
268
J J/30 Seward, AK
How do you plan on plumbing that? You'll need a long fuel line from your main tank then a shorty to the heater.
I think I would put the day tank in a stern locker and run the fuel line in the bilge, up inside the locker ahead of the heater and through a small hole in the bulkhead to the heater metering device. I know that takes away from storage but you don't have to live with it inside.
The purpose of the day tank is to gravity feed the heater. I am pretty sure that the place I have planned for it is the only place it will fit.
 
Jan 5, 2017
2,263
Beneteau First 38 Lyall Harbour Saturna Island
From the pics it looks like your heater may be a little higher than mine was but my tank was mounted right under the deck aft. and I had no trouble with it. 5200 a piece of 3/4 ply against the hull and screwed the tank there. I know they are shiny et.al. but I think you would be happier if it wasn't in your living space. IMHO
 
Nov 15, 2015
268
J J/30 Seward, AK
From the pics it looks like your heater may be a little higher than mine was but my tank was mounted right under the deck aft. and I had no trouble with it. 5200 a piece of 3/4 ply against the hull and screwed the tank there. I know they are shiny et.al. but I think you would be happier if it wasn't in your living space. IMHO
Can you elaborate on where you put the pump, lines, etc? What kind of lines did you use?
 
Jan 5, 2017
2,263
Beneteau First 38 Lyall Harbour Saturna Island
Main tank in the 28 was under the 1/4 berth. Ran the fuel line across to the port side ( through a filter) then up to the pump ( pump will lift 6 feet) into the tank. Outlet ran down to the bilge. Through the under settee storage into the hanging locker the heater is mounted on. Used marine grade diesel fuel line for all. Pump was mounted on the same board as the tank.
P.S. Primary racor was right beside the main tank so came off the second outlet of it.
 
Nov 15, 2015
268
J J/30 Seward, AK
Yeah, I don’t think sure a gravity feed from the day tank to the heater would work with the tank mounted aft. At the moment I am thinking I should run a vent straight back along the top of the cabin to the main tank vent on the transom which exits at the same height.
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
Hhmmm... How about just small a vertical tube with a shutoff valve when not in use?
 
Jan 5, 2017
2,263
Beneteau First 38 Lyall Harbour Saturna Island
You could also not use the day tank and run straight off the pump. That's the way it is on our first 38. Pump is under the foot of the aft berth, heater is on the heads bulkhead. You hear the pump if you listen for it but it disappears pretty quickly. No need for a vent then.
 
Nov 15, 2015
268
J J/30 Seward, AK
You could also not use the day tank and run straight off the pump. That's the way it is on our first 38. Pump is under the foot of the aft berth, heater is on the heads bulkhead. You hear the pump if you listen for it but it disappears pretty quickly. No need for a vent then.
Yeah, that was the reason for the day tank actually, to avoid having to hear the pump. Call me picky :)
 
Jan 5, 2017
2,263
Beneteau First 38 Lyall Harbour Saturna Island
Same reason I put one on the 28. I was disappointed that this boat didn't have one too but your brain stops hearing the pump after a minute.
 
Jan 5, 2017
2,263
Beneteau First 38 Lyall Harbour Saturna Island
Yeah, I don’t think sure a gravity feed from the day tank to the heater would work with the tank mounted aft.
Your pic show the metering valve about 30 inches below deck level so gravity should work just fine if you mount the tank just under the deck. Distance from the tank doesn't matter.
 
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Nov 15, 2015
268
J J/30 Seward, AK
Your pic show the metering valve about 30 inches below deck level so gravity should work just fine if you mount the tank just under the deck. Distance from the tank doesn't matter.
You may be right. I am just having trouble finding a straight enough path for the fuel line to the heater. But anyway, it's a good idea.
 
Jan 5, 2017
2,263
Beneteau First 38 Lyall Harbour Saturna Island
Don't worry about a straight line. Rubber fuel line goes anywhere.
 
Nov 15, 2015
268
J J/30 Seward, AK
Don't worry about a straight line. Rubber fuel line goes anywhere.
I was thinking more in terms of avoiding section where the gravity-fed fuel line has to go through a section of rise. It is hard to find a way where every turn is downward over that length.
 
Jan 5, 2017
2,263
Beneteau First 38 Lyall Harbour Saturna Island
A long as you don't go back up higher than the tank you will be OK.
 

LloydB

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Jan 15, 2006
804
Macgregor 22 Silverton
After having drained several fish tanks and a rain filled cockpit from time to time it still amazes me how high a siphon will pull through a 50ft 3/8" hose.
 
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Mar 26, 2011
3,400
Corsair F-24 MK I Deale, MD
Not the potable water vent. I'm hoping that was a joke.

One possibility would be to run the vent back to the main diesel tank. In that way, if you overflow by loosing track of time, it just goes in a loop.
 
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