Holding Tank Vent Question

[Geoffreykwright]

Hi - I've got a question about the holding tank vent.  I've not re-routed the vent on my 34 Mk II (hull 1494, Y2K).  Still runs up thru a port-side stanchion.  I've seen vent air-filters which are available - presumably these would attach to the hose between the tank and the stanchion.  Has anyone had any experience with these?  Occasionally we get a whiff of the holding tank in the cockpit depending on the wind direction.   (We do our best to pump out regularly and we do use a tank conditioner).  Thanks in advance.

[britinusa]

Mk 1 here.

We had the sniff issues too!

I replaced the stanchion, and the hoses from the tank to the vent, including adding an elbow joint to avoid the kink that we had just below the stanchion connection.

We use Odorlos and pump out very often.

That has cured the swift sniff issue.

As it happens, trying to eliminate all sniff issues in the cabin, so, I'm about to replace the hoses from the head to the tank and tank to Macerator - macerator to waste pumpout fitting.

Paul

[Roc]

Peggie Hall does not advise using vent filters because they actually stop the free flow of oxygen into the tank, which makes the anaerobic bacteria thrive (that's what causes tank smell, you want aerobic bacteria, which needs air flow).  I kept my original stanchion vent, but per her advice, added a larger vent.  I cut a hole into the tank access cover and routed the vent line forward, through the side storage area, into the locker in the v-berth port side and out the hull below the sheer stripe.  You have to remove the port side cabinetry by removing the screws on the outer frame.  The whole modular unit will come out, frame and all.  She advised to make the run more of a 45 angle rather than straight up, for better air flow.  She suggested keeping the original vent for better cross ventilation.  I put a dose of odorloss at the end of being on the boat for the weekend, or extended weekend.  No "boat" smell.

[Dave Spencer]

What Roc said.   
I got the same advice from a phone call I had with Peggie Hall several years ago.  Here's my project:
http://c34.org/bbs/index.php/topic,6861.msg45889.html#msg45889
Roc's looks better since he has a shallower slope on his forward vent hose.

[Geoffreykwright]

Thanks to you all for your sound advice!

[rmbrown]

Roc, what messes with my head is that you have vertical clearance above your tank to run that vent without a dip.  Mine runs across the top of the tank but has to dip a bit to get under that fiberglass lip, making a water trap of sorts.

[Noah]

I may be wrong but I think the MK11 might have l a smaller holding tank than the MK1?

[Mick Laver]

Not hard to imagine. I measured mine at 13 gallons to the very tippy top.

[rmbrown]

Or the same tank... mine's B-179 from Ronco... but the locker is a little deeper.  I hadn't considered that!

[TortolaTim]

Just got our 1989 a couple of weeks ago and am running down Peggie's list of odor control measures. I've read up on all the discussion on this topic and would like to add a 1" vent to my holding tank. It seems that there is VERY LITTLE space between the top of the tank and the cushion board, like 1" or less. I am wondering what my options are. Would it be feasible to put the outlet fitting as far forward and as high as possible on the port SIDE of the tank?

[rmbrown]

I have the same problem.  We could put it on the side of the tank, but I'm guessing we'd then have to give up the top 1" or more of tank capacity and I really hate to do that.

[dw]

Can someone tell me the size on the vent hose and the number of feet needed to replace this?   My wife and I recently purchased a 1988 Catalina 34 and are working our way down the list. Boat smell and cushions smell is at the top, followed closely by hatch leaks.  The cushion in the main salon are the worst but with baking soda and sunlight we are ahead of the game there.  We will be using a dry fabric cleaner on the upholstery.  I would like to order a replacement vent hose but even though this was the primary reason to stop by boat yesterday we got side tracked and did not get the hose size.   This appears to be very reasonable price hose here https://www.marinesan.com/5-8-MaxFlex-Sanitation-Vent-Hose-p/306345650.htm

I posted in an older thread before finding this I do not see the hose size referenced?

Thanks in advance.

Dwight
Hull 694
GET 'N BY 

[TortolaTim]

Dwight, I don't know the vent hose size offhand but I can offer a bit of advice with the smell. We bough our boat last month, and the smell was pretty bad when opening up the boat. I worked my way down the list and replaced the sanitation hose from the head to tank, and tank to pump out. It made a HUGE difference! I bought 1.5 inch Trident II hose from Defender. Install was surprisingly easy and not too "uncomfortable."
Cabin smell improved by 80%.

[Stu Jackson]

I'm on my boat now:

horiz diagonal from tank to rise behind the woodwork:  4 feet

vertical rise:  4 feet

horiz to base of stanchion:  1 foot

Wiggle room:  add another foot (it is, after all, YOUR money!!!:D)

However, if I was doing it, I'd go for the mushroom vent on the hull side and forget about the vented stanchion.  Check out the 101 Topics for how to do that.

[mregan]

I replaced the stanchion vent with a thru hull vent located below the rub rail on the port side.  Went across the top of the tank, up behind the port cushion, into the small locker above the elec. panel and out the side of the hull there.  Went with 1" hose. 
When we bought the boat the smell was horrible.  Replaced the tank and all of the hoses.  Had a 2nd opening installed in the tank top.  Put a plug in the 2nd opening with a 1/4" hose through it and dropped into the bottom of the tank.  Other end of the hose I connected to a fish tank bubbler.  Read Peggie's book.  Figured the air being introduced into the tank from the bubbler would provide airflow and the aerobic action to eliminate the smells.  Hasn't worked as well as I wanted, although we aren't as diligent as we should be with pumping out.