Holding tank ventilation

[Steve Laume]

I have always thought the 1/2" holding tank vent line was a bit small.

I picked up a 3/4" vent at the consignment shop and have finally gotten around to installing it. I had replaced all of my sanitaion lines a couple of years ago but had never messed with the vent line. It was attached to the holding tank with a plastic elbow, just gooped in place. The line traveled along the port side of the engine, up and across the boat under the bridge deck and then all the way out to the hull joint before making it's way back to the vent. Any sags or dips could potentially block all functions and that is a very small tube.

I drilled out the hole and installed the larger vent fitting in the stern. At the holding tank, I used a 3/4" bronze, through hull fitting with a 45 and a hose barb. This makes for a very secure attachment to the top of the holding tank. Yes you do have to reach in there to install the through hull but it is a small price to pay for knowing it will not ever leak. I ran the 3/4" hose straight back along the port side of the engine and then up and along the inside face of the cockpit locker. It runs just below the engine exhaust. When I got to the stern I took a loop up to where the backstay is attached and then down to the vent fitting. Taking this route made for fewer bends and kept one more hose from the rather cluttered starboard side. It also reduced the run by 4 or 5 feet. I am very pleased to have finally gotten this job done.

Those microbes need their air, Steve.

[Keith]

Steve,

I'm curious, my 30c 1980 holding tank is under the v-berth and vents directly above it on the starboard side bow. There is only a short vent hose maybe 3 or 4 ft long. not sure of the dia will have to check. So my question is where is your holding tank located and why run the vent anywhere near the engine?

Just curious

Keith

[Steve Laume]

At some point between 1080 and 84 Cape Dory moved the holding tank on the CD-30. The one on Raven is a glassed in tank that sits in the aft end of the bilge. It goes from about the raised up section of the cabin sole back under the engine.

Like everything else in life, it is a compromise. It keeps the weight low and centered in the boat. It also makes for very long sanitation hose runs and reduces the bilge capacity by 20 Gal. The vent line seemed very small, considering the length of the run and the number of bends. The vent exits through the transom on the starboard side.

The pump out fitting is in the cockpit sole, which seems like a great location.

I suppose the bilge is also a good choice of locations for the holding tank if it was ever to leak, Steve.

[Sea Hunt Video]

For what little it may be worth, the holding tank on S/V Bali Ha'i (1982 Cape Dory 25D, Hull No. 0069) is located just forward of and below the Yanmar. It is about an 18' run from the forward marine head (a/k/a V berth) to the holding tank - a very long run in my mind. The pump out fitting is in the cockpit, port side near the scupper drain. The vent hose runs (about 7') from the holding tank along the starboard side of the engine and vents at the transom next to the boarding ladder. I have given some thought to replacing the vent hose since I am also replacing the marine head, the sanitation hose from the head to the tank and the sanitation hose from the tank to the pump out cap. The difficulty is in gaining access to the connection between the hose and the vent on the transom.

[David Morton]

Robert, I don't mean to hijack the topic, but as long as you mentioned you are replacing your sanitation hoses I wanted to encourage you not to go cheap! I just finished replacing the wire reinforced vinyl hose the PO had installed and what a stinker it was!! Practical Sailor did a permeability test some time ago and recommends Trident 101/102 or Shields Poly-X.
http://www.practical-sailor.com/issues/ ... 763-1.html )
After installing the Trident hose the cabin smell was completely gone. Plan on $11 - $20/ft (the Trident is less expensive, not cheaper!!). I used about 14 ft from head to tank and 4 ft from tank to pump out. And wear gloves!

David

[Sea Hunt Video]

David:

Thanks I pulled all of the sanitation hose and will be replacing with Trident; as you stated, this is recommended in the April 2012 issue of Practical Sailor. I think I am ordering Trident "SaniShield" 102 (white); 1 ½” diameter. I had planned on ordering about 25' (better too much than too little) from http://www.Defender.com

Unfortunately, this project has slipped down the priority list since it can be done once S/V Bali Ha'i is back in the water and on her mooring at the sailing club.

Hopefully, Steve is not too upset at the brief "hijack".

[Steve Laume]

"The difficulty is in gaining access to the connection between the hose and the vent on the transom".

Once you get done replacing the sanitation hoses the vent line will seem easy no matter where the connections are.

This and many other jobs and inspections can be made easier by installing an 8" inspection port in the vertical surface at the aft end of the cockpit well. I installed the port years ago and it was the only way I have been able to do a lot of the work in that area by myself. Even if you have help it will make those jobs much easier.

These would include, working on the back stay connection, manual bilge pump, installing wind vane, bilge vent hoses, bilge blower, all the vent lines, and the traveler on some boats. Raven's engine panel is mounted on the side so it is not an issue. On the CD-25, you might have to move the inspection panel off center or just pull the engine panel to gain access to that area.

Even pulling the panel would be much easier if you could get your hand in there to hold the nuts on the back side, Steve.