Our 97 35' has always had a bad obor in the rear closet and the head is usually stinky also. I finally roused myself into action and discovered that the knuckleheads had placed the holding tank vent right at roof top level, just aft of the head's vent hood. This leads to fumes entering the head unless you kept the vent hood closed. Also, the hole in the roof for the 1.5" pvc vent pipe is about 1/2" larger than the pipe and is NOT sealed to the pipe. This allows fumes to enter the rear closet.

I removed the vent cover and installed a 2 foot section of 1.5" pvc ELECTRICAL CONDUIT not pvc sch 40 plumbing pipe. The conduit has the female joint already formed in one end. BEWARE !!! The existing vent pipe is NOT permenently attached to the holding tank. Whatever you do, DO NOT , put any upward pressure on it. I shortened the female joint on the conduit so that there is only about 2" to slip over the existing pipe. I also sanded the interior of the joint to slightly decrease the tightness of the fit.

Before installing the conduit you need to drill a couple of rows of holes in the top to allow air flow. I capped the top with a 2" cap from the plumbing section of HD. Currently my cap is just sitting on top of the conduit bit I have several ideas about permenently mounting it. I remounted the original vent cap back to the roof [ unfortunately the vent cap was not centered from the factory so I had to drill new mounting holes and fill the old ones ]. In the plumbing section you will find a rubber 1.5" to 2" pipe adaptor. This is a good fit on the conduit and the 2" section will barely fit the top of the vent cap _base_. Discard the original, removeable cap. Clean up the _base_ good and use some quality sealer when screwing back to the roof.

I used grease to help the conduit slide easily over the original vent pipe and some more grease to slide the rubber adaptor down over the conduit. Do not clamp the 2" end of the adaptor. Do not force the rubber adaptor too far down over the vent cap _base_ or the conduit may be lifted up off the vent pipe. I used some 1" strap aluminium to make a brace from the roof rail over to the new, taller vent. A hose clamp is fine for attaching the brace to the conduit.

Matls:

1.5" x 10' Elec pvc <$5.00

1.5" to 2" rubber adaptor <$5.00

2" PVC cap <$2.00

1"x1/8" x 4' alum strap < $9.00

SS hose clamp , 3/16" pop rivets - in the garage.

I can send pics if interested.

Wouldn't it have been easier to just run a new vent out the side of the
hull (which is where it should have gone in the first place)?



A nice short, straight horizontal (or as horizontal as possible to keep
it above waterline) 1.5" vent--better yet, two- and Odorlos in the tank
used according to directions should keep the system aerobic, preventing
the waste from creating odor



A single vent to the roof hasn't got a prayer of keeping the tank
aerobic...but a second vent out the side to provide the "draw" needed
to turn a vent to roof into a "chimney" should provide enough air flow
though the tank to work, too.

Peg ! I have your book !

Myacht uses a section of the pontoon as the holding tank. At the factory level it would have been easy to add the second vent at the front of the tank. Very difficult once the boat is in the consumer's hands.

We have thought about sitting a small fan on top of the toilet seat and introducing some air into the tank a couple of times a day . The toilet dumps straight down into the tank so blowing air while holding the pedal down would do the trick but would be a pain in the ...................

Would the fan deal work ?

A fan would help, but only if it ran 24/7/365. An occasional
"shot" of air wouldn't do a thing--in fact, would prob'ly INCREASE the
level of odor out the vent... 'cuz the contents would just turn
anaerobic again between the shots of air.



Adding or moving a fitting isn't nearly as hard as you think...access
to the tank can be the hardest part of the job on many boats--a problem
you don't have. Austrailian Global Services ("AussieGlobe" at
A.G.S. Australian Global Services
(who also makes the most odor resistant sanitation hose on the planet)
has a li'l doodad they call the "uniseal" that actually makes it a
piece of cake if you're at all handy with a hole saw. And it costs next
to nothing.



Put one at the front end of the tank, the other at the back end...on to
the top of the pontoon. You wouldn't even need any hoses, just a
90 radius facing forward on the front one...you'd have air screaming
through the tank. Your pontoons would have to submarine to put any
water into the tank, so no worry on that score either.



Why didn't we have this chat BEFORE you did all that work that didn't
accomplish anything except to redirect the odor away from your head air
intake dorade?

Myachts have flattopped, slab-sided pontoons. I think you would have to disassemble the boat to get access to the top of the pontoon.

ANYWHERE? Even on the side at the top???



Vents don't have to be ON the top, just high enough to keep 'em out of the water.

It would be easy to add a fitting a run a 1.5" pipe up the side of the boat . It would look very nice ! Would also be easy to knock it off.

I could run a flat piece of sheet alloy or plastic down the center of the existing vent pipe effectively dividing it into two pipes. I could then put a "Tee" on the top of the divided pipe so that the breeze would force air down whichever opening of the tee was facing the wind. Probably wouldn't be very effective because of the closeness of the inlet and outlet in the tank.

Why would you run anything up the side of the boat? If you're gonna do
that, you might as well live with what you've done, 'cuz another tall
vertical pipe defeats the whole purpose of installing new vents.



It SHOULD be a relatively simple matter to put two 1.5" holes in the
tank as close to the top of it as possible, and install two 90s
(visualize a 1.5" PVC elbow tank fitting), one facing forward the other
aft. If you're worried about knocking 'em off, put em on the
inside, under the boat. You'd have to beach the boat over the top of a
rock tall enough to scrape the bottom of the boat to knock 'em off.



Or you can keep what you have and let any boats downwind of you wonder where the odor is coming from...



Btw...I was on Lanier for more than 25 years, so know it well. Where do you keep your boat?