Clamshelled thru-hull

[Marc Bergmueller]

Does anyone manufacture a 1" thru-hull with a clamshell on it. I'm replacing the puny 1/2" tank vent hose and don't know what I should do to funnel more air in the tank. The boat is a Hunter 310. If anyone has done this, I'd like your input.
I also plan to use K.O. but the po used the green/blue nitrate stuff, which didn't work. How should I flush the tank, so the K.O. lives?
Thanks

 

[Steve Dion]

Marc:

Before you mess with the vent hose, try Odorloss.

Most of the active boaters in our marina have switched it and have been pleased.

 

[Marc Bergmueller]

Thanks Steve, Peggy has recomended in the past to go with one inch hose so I wanted to give that a try

 

[Rich Stidger]

No clam-shell needed IMHO

When I converted my vent hose up to 1" diameter, I simply used a 1" thru-hull. I think my original was a straight thru-hull also, but I can't find any old pictures to confirm.

The smaller fitting next to the larger 1" in the picture is my shower sump output.

 

[Steve Dion]

What good is a bigger hose/fitting if the vent fitting on the tank is 1/2"?

I think a straight through fitting like Rich is showing in his post will probably help nearly as much.

 

[Rich Stidger]

Oh, I forgot to mention that I converted to the larger 1" size when I replaced my holding tank. I had a 1" vent fitting installed in the tank also.

 

[Stu Jackson]

While not specifically the original question, there's a picture of a relocated vent fitting in this thread:

http://c34.org/bbs/index.php/topic,6293.0.html

Clamshell covers never come with thru hull fittings, they're two separate things, purchased separately.

You also do NOT want the clamshell facing forward, 'cuz when you're sailing you'd fill up your holding tank, and the concept of the clamshell is to avoid water ingress, NOT to use it for air ingress 'cuz that wouldn't be helpful due to the small area involved. The clamsheel isn't to "scoop air" it's to avoid water coming in.

FWIW, I have maintained our 5/8" vent and once I started using Odorloss the smells are gone. OH, also I replumbed my sink drain to the head intake and do a "last flush" with fresh water.

Smells are gone.

http://c34.org/bbs/index.php/topic,5755.30.html

 

[Peggie Hall HeadMistress]

Weelllll...try the easy stuff first

Thanks Steve, Peggy has recomended in the past to go with one inch hose so I wanted to give that a try

Stu has had good luck using Odorlos in a tank that has only a 5/8" vent...so while I do indeed recommend a 1" vent--even 1.5" on larger boats--I'd flush out the tank and give Odorlos a try before doing any surgery, 'cuz you'll have to replace both the vent thru-hull and the tank vent fitting to upgrade to a 1".

I've posted directions for flushing out a tank at least a dozen times, so you should be able to find 'em fairly easily in a search.

 

[Sunbird22358]

When I asked Peggy about solving the odor problems from the holding tank on our old CAL 21, one thing she mentioned was moving the vent thru-hull fittin from the side of the cabin to the side of the hull (just below the gunwale). We had previously had a 90deg bilge-pump exit thru-hull as a vent fitting on hte cabin side. I was VERY surprised when I installed the new (straight) thru-hull at the blast of fresh air that flowed into the boat while sitting on the cradle on shore! I don't think the boat was pointed so that the opening faced the wind that day...... but WOW, what a flow of air! I suspect that a cowl (clamshell vent) over that opening would have actually reduced the airflow. Just the movement of air past the thru-hull (mushroom head) was drawing air into the tank.