Permeated holding tank... is that possible?

[Peggie Hall]

Where's the tank located in the boat?  Forward? Midship? Aft? 

[Ken Juul]

The tank is midship, port side.  Borrowed a couple pictures off the c34 Flickr site.  The first one shows a MKII with ~15° heel.  Notice the wave pattern, the other side will be the same.  Placing a vent near the forward window in the hull should keep it out of the water when heeled. The second picture is a MKI.  Not quite as easy to see, it looks about at the same angle of heel, again the wave pattern suggests that the vent will be clear of the water if placed about where the split in the cabin window is.

Will someone still lucky enough to go sailing take some pictures of the boat heeled 15-20° to confirm.

[Peggie Hall]

Run the vent as far forward as 5' will let you, and try to keep the vertical rise below 45 degrees.

Oh, one more thing...  The vent fitting should be on the top of the tank at the bow end, next to the edge that's closest the centerline of the boat...AWAY from the hull.

[Exodus]

I replaced my vent hose and installed a new through hull just below the rub rail and a few inches aft of the old vented stanchion.  I first attempted to go up to 1" vent hose but there was just not enough space above the top of the tank to accommodate a 1" hose.  I wound up staying with the 3/4".  I also removed the vented stanchion and replaced it with a regular stanchion. 

[Indian Falls]

Exodus,

Can you let us know if you find any appreciable differences in tank smells with this change in venting?
It's certainly will have less chance of clogging with "stuff".  What were your tank smell problems prior to this?  If any?  What was your reason for making this change? Is the new location keeping gasses from the tank from stinking up the cockpit when the head is pumped?  If you didn't have smell problems, how did you achieve that?  Thanks!

[Exodus]

Indian,

Yes, the new vent hose helped considerably with my odor problems.  I replaced all sanitation hoses except the pumpout hose and the small hose between tank and macerator at the same time.  The vent hose though appeared to be the major source of my odor problem. 

I have not been able to detect any odor on the outside of the boat with this vent placement.

Also, since I am mainly a weekender, we only use the head for liquid waste and also use fresh water from the sink to flush.  At the end of the weekend I make sure I pump enough fresh water through the lines so clean water only is left in the line.

[hump180]

Exodus, I am interested in doing your version of this mod. Have you sailed her hard with this mod? Any water into the new thruhull?

[Exodus]

I have been out in 18-22 knots with no reef in the main and water did not get close to the through hull.  If any water were to enter it will only end up in your holding tank anyway, but I really don't think that it is an issue.  I placed the through hull as high as possible just below the rubrail.  FYI the hull is very thick in that location probably 2" or more.  The threaded portion of the throughhull I bought was just long enough to go through and tighten up the nut on the other side.

I had written this up with pictures at the time but the post did not work and I did not try again.  If someone can PM me and tell me how to post pictures I will do so.

[Stu Jackson]

I had written this up with pictures at the time but the post did not work and I did not try again.  If someone can PM me and tell me how to post pictures I will do so.

There are about four different "posting pictures" articles if you do a search with the quote marks.  Each of them may answer your specific question without cutting & pasting them all here.  Depends on what you need to know, but I'm sure you'll find what you need in those links.

[Ken Juul]

It would be good material for the Tech Wiki also.  Be happy to add it if you email me the text and pictures.