Water tank venting.

[melp64]

For the last few months, I have been tearing apart the saloon and the galley, and the saloon and the nav station areas. All of this because the PO didn't maintain the vents of the water tanks that are vented thru the stanchions on the deck. I don't ever want to have to do this again Is there a different way to vent these tanks beside going thru the deck were leaking is possible. Couldn't the vent hose go up to the bottom of the deck and then loop down to the bilge? I am guessing that the hose goes to the stanchion so it you over fill it the water would exit out the stanchion.

[mdidomenico]

my '89 aft water tank vents into the cockpit behind the wheel.  i plan to route my forward water tank to the same vent.  it's a long reach, but seemed like a good idea.  the waste tank is vented to a 1" thru-hull i drill way up by the rail.  i glassed over and sealed up the stanchion vent holes through the deck

[melp64]

I know that I have the aft cabin tank and I never really checked to see were that one is vented to. What tank is vented by the nav station? Let me know how that works out for you. I am planning on running a lot of pex piping and that doesn't seem like it would be that hard while I'm running pex that way anyways.

[KWKloeber]

Stanchion bolts can leak. Are you planning to remove them and glass up all those holes?  How about blocks and winches?

Do you really want a hose that not only occasionally pees but, for the remainder of the time, sucks connected to the bilge area?

Rather than re-running hoses why not simply bed them as they should be in butyl, add backing plates, and not need to touch them for 30 years at least?

[Jim Hardesty]

I agree with Ken, leaking stanchion was the problem.  Not the vent.  When you have them off call Garhauer for backing plates, much better than the washers.
Jim

[Ron Hill]

Guys : The two vented stanchions (holding tank on port side and the starboard fresh water tank on the starboard) need BACKING PLATES.

As Ken mentioned you need to clean out and glass/epoxy in those holes. Then redrill Also mentioned is butyl rubber bedding is needed on ALL stanchions.

It just so happens that both of the vented stanchions are at the beamiest part of the boat. People on the dock trying to help, invariably grab those stanchions.  I've even put NO PUSH on those stanchions, but it doesn't do much good.  That's why backing plates are a MUST!!

A few thoughts

[Ted Pounds]

What Ron said! 👍👍

[melp64]

Stanchion bolts can leak. Are you planning to remove them and glass up all those holes?  How about blocks and winches?

Do you really want a hose that not only occasionally pees but, for the remainder of the time, sucks connected to the bilge area?

Rather than re-running hoses why not simply bed them as they should be in butyl, add backing plates, and not need to touch them for 30 years at least?

Isn't the vent line just to let air out of the tank when your filling it. couldn't you let it get air from the inside the boat and why would it pee once in a while (from over filling???) I have already fixed the stanchion I used butyl tape and had to use two layers on one side where the base is bent probably from people pulling on it.
I was going to take pictures for the update post but I found myself tearing the countertop off by the nav station. With damage coming from the same vent hose on that side of the boat. I usually stay up beat but this one you might say I was venting,

[KWKloeber]

Yes, peeing when over filling.  I simply let my hose run until I notice it peeing - no need to waste time hanging out there waiting.

It's a closed tank - when you draw water the vent is two-way - whether it's vented thru a stanchion or vented thru a host to (heavens forbid) the bilge 

The proper fix is not to add more goop.   
It's to remove a damaged (bent) part, straighten it, and reinforce the installation with a backing plate (on all of them preferably.)
But, YBYC of course!

[Ron Hill]

Guys : Like I've previously said - I only fill the starboard tank in the spring from the deck fill.  There after I gravity fill from the aft tank.  So the filling and peeing only happens once a year for the starboard tank.  Then I always refill only the aft tank and that overflow vent is on the vertical outside wall of the aft lazarette (standard transom).  That peeing (overfull) is into the cockpit floor.

Using water from the starboard tank and refilling from the aft tank is the way I manage my fresh water usage!!

A few thoughts

[Noah]

Ron-  as you know not all boats are the same in all things. My boat has a "Y" valve on water tank system so I can select either tank to use but no way to fill one from the other. Some POs idea I guess?

[Ron Hill]

Noah : Yes a POs idea. There have been a couple of Mainsheet tech note articles and plumbing in a " Fresh WATER Manifold"  I like the way the factory plumbed fresh water. The only change that I might have made is to use a ball rather than a gate valve for each tank!!  I believe that your "Y" valve is in the minority of Owner Improvements!!

Note that the MKII C34s are plumbed like the MK Is except that there is a forward rather than a starboard fresh water tank and I believe that you can gravity fill the fwd tank from the rear tank.

a few thoughts

[melp64]

Ron and Noah

After tearing out most of my boat I can see a couple of things that I would change from the the way it was originally built. On both sides the galley and the nav station the small divider that separates the saloon went all the way down to the fiberglass with the countertop notched around the divide allowing the vent line when it would (pee) or in my case leak from the stanchion the water would follow the divider down to the fiberglass and then under the countertop.
When I put this back together I am going to run my countertop under those two dividers and seal the countertop to the hull. If it was to start leaking it would come out on top of the countertop instead of underneath where its out of site out of mind.
I really like the idea of running the vent back to the rear tank vent. This would eliminate the leak issue there, will the length of the pipe going to the vent create more problems? If one of the stanchions did leak is there a way to make sure the water gets to the bilge without hurting any of the bulkheads or woodwork. I like the idea of gravity flow from the aft tank to the forward tank is there a way to fill the aft tank and have it then fill the front tank? This way you are only filling the tanks from 1 location. I ask all these questions as I am in position to implement some new plumbing ideas that may  eliminate  some leaking problems. After reading all the post on this same problem I can only imagine the amount of mold that is growing under peoples countertops. How many times a year or five years does someone open the small compartments that are on the saloon shelfs.
If anyone has a good suggestion Im open to all suggestion. Almost everything that I have done on the boat in some way has come from this site, either my posts or searching the post on this site.

[Noah]

Fix the bent vented stanchion (or replace with new one from CD), use backing plate, butyl, and you should be fine/done. IMO—Interior structural cabinetry redesign is a waste of energy. Go sailing instead!   I NOW always check these spots for leaks in my boat, since I had a leak there in the past and made appropriate repairs. No problems since—but I always look! Maybe consider running a new bigger vent for the holding tank on the side of hull at deck level, as some have done for better holding tank performance. Lots here on website about that. But I have NOT done that and so far have had no issues with holding tank performance.

[Jon W]

As several have said, the leaks are most likely coming from the fasteners or the stantion base. Remove them all, clean the fasteners, bottom of stantion base, and deck thoroughly with acetone. Fix anything bent. Apply bed-it-butyl tape per Marine How To website. Install backing plates on all stantion bases. Catalina Direct sells them for around $12.60 each. I also put backing plates on the pushpit, pulpit, and gate bases. I changed vent hoses and clamps, but the vent runs are unchanged. Did this 8 years ago, I have zero leaks.