Installing Vent for Holding Tank through the hull

[Mike McDonald]

Hi all,
Back again for more suggestions.  I had a dock mishap on Sunday, and took out the vented vertical stanchion on the port side, the one with the holding tank vent in it.  I've read several posts on re-routing the vent hose through the hull, with different approaches.  After I repair the deck, I plan to install a new stanchion without the vent.  I ordered one from Garhauer. 
It appears that others have located the through-hull vent more forward than where it currently is located.  Is there any reason not to install the through-hull vent approximately below the current stanchion vent?  I haven't measured the location yet, but my thought was to put it either between the rub rail and the stripe or just below the stripe, depending where I have access from inside.  I seems like that would be easier than re-routing the vent hose forward.  It also seems like it might be better from the standpoint of water getting into the vent opening when sailing.  I'll try to get some measurements today or tomorrow to see if I have room inside the slider door above the nav station.  Also, I plan on using a standard Marelon mushroom through hull, rater than a covered vent.  Seems others have used them with no problems.  I would appreciate your thoughts on this.  Thanks.
Mike......

[Les Luzar]

Mike,
That vent stantion is close to mid-ship. If you locate the new through-hull under the rub-rail at mid-ship, and you are sailing hard on the wind,  your rail will be in the water, and that vent could be submerged and begin taking on water. Moving it forward eliminates this problem.

[mregan]

I just did this project.  I located the vent right below the rub rail.  Where the vent comes up through the shelving in the cabin, I turned it towards the stern, poked it into the cabinet (where the plexiglass sliders are located) then out the hull.  I read some older threads here where a couple of people had done this.  Someone had mentioned you could put a clamshell cover over the vent thruhull facing the stern.  The water flowing over the clamshell would prevent water getting into the vent when heeled way over.  I figure I try it out this summer without the clamshell and see how it works.

[Ken Juul]

I haven't run the hose yet, but I just installed a 3/4" thru hull between the rub rail and the stripe.  It is centered under the forward salon port which is about where the plastic sliding doors overlap.  Standard Marlon mushroom type.  Looking at hulls heeled, midships is generally between the bow and stern wave, it should stay out of the water.  The C34 groove is about 18-20° heel, if the rail is in the water you have too much sail up and are loosing speed rather than increasing it.

The idea of adding a new vent is to make it easier for air to get into the tank. Shortest most direct route is best.  Also there is alot of cabinetry in the way if you try to install one near the old stanchion vent.

[Mike McDonald]

Thanks everyone for your thoughts.   

Ken, where did the through hull actually come through in the the cabin? I'm not totally clear on your location.  Is yours centered under the forward "opening" port in the salon? Did it come through the ash panel above the slider? Or did it come through inside the cabinet with the slider?  If you have a picture that would be great.  If not, just a description would help.  Sounds like a good location.  Thanks.
Mike....

[Ken Juul]

will try to remember to take pictures this weekend.  It comes through the ash battens above the shelf.  It is centered under the aft opening port.

[Mike McDonald]

Thanks Ken.  That Helps.
Mike.....

[Steve W10]

The PO had done this to my boat and I think it was a great idea.  He did both the waste tank and holding tank vents.

Hope the images help.

Steve

[ghebbns]

This is going to sound like a stupid question, but what is the difference between a holding tank and a waste tank?  I have always used the terms interchangeably.

Thanks,

Greg

[Steve W10]

Sorry Greg, I likely messed that up.

What I meant by holding tank was the fresh water, domestic.

Waste on the Port, domestic water for the sinks on the Stbd.

[Fred Koehlmann]

Hi Mike,

Losing that vented stantion is a blessing in disquise (IMHO). Not only is the ventilation inadiquest, but we found that it was a bad source for leaks. Everyone grabs that stantion and the bedding eventually goes (before the other stantions) and you get a leak where your electrical stuff is.

Last year we replaced our holding tank and ran a 1" hose forward and up and out behind the foward port locker. The mushroom vent is below the rubbline and above the strip. It works well and the best part is that when we pump out we send the water in through the vent and really clean the tank out.

With the vent in the forward location it also does not go below the waterline (it would have to be a real nasty sea, which we have had occasionally).

Cheers, Fred.

[mregan]

Here is a picture of my relocated holding tank vent.  Same idea as Steve but mine turn aft vs. foward.  I also relocated the water tank vent to just above the hanging locker in the v-berth.  Came up in the boxed in area where the water tank fill comes down on the starboard side.

[Mike McDonald]

Thanks for all the idea's and pictures everyone.  Seems like everyone located the thru hull different places.  Any problem with water coming in the thru hull above the nav table mregan?  What kind of thru hull did all of you use.  Do you think the cover over the thru hull is necessary?  Thanks.
Mike....

[Ken Juul]

I still haven't run the hose yet but this is the thru hull.  White marlon 3/4" from WM.  I plan on using both vents.  The experts say more air is better for reducing holding tank odors.  Been getting ready for opening day at the YC.  Still need to reglue the ash strips and plan to hide the hose at least in the shelf above the sliding doors.

[Roc]

Here are some pictures of the vent line I installed. I actually called Peggie Hall when I did this and she advised the following.  Don't make it go straight up, but the hose should have a gradual slope.  Use the largest hose possible.  Don't use an elbow, but a large radius for the hose as it exits.  I see some have used an elbow.  I installed the new vent hose in the inpection port cap, leaving the original vent still in use.  Peggie suggested that would help with creating a cross ventilation.  The hose exits just below the rub rail, from the port side locker, with a large radius leading to the thru-hull.