CD30 Holding Tank Vent

K_LeMans · Post by **K_LeMans** » Sep 6th, '11, 12:39

I'm wanting to replace my holding tank vent with one of the lovely spartan items. They make two kinds, one for a straight hose connection, one with a 90 degree adapter for the hose approaching the vent at right angles.

Anyone know which one works on a CD30?

Maine_Buzzard · Post by **Maine_Buzzard** » Sep 6th, '11, 19:56

I have a straight vent in Guppy. I had to tee it for a vacuum breaker vent line and it is placed in the starboard side of the chain locker, near the deck.

Kinda scary how crudded up the clear vent line is. I'll probably gut the entire sanitation system this winter and rebuild with new hoses and hardware. It's the one thing on the boat that I can probably never get to work perfectly.

Larry DeMers · Post by **Larry DeMers** » Sep 7th, '11, 19:25

Hi,

I use an elbowed vent, with a screen to keep the bees out.

A suggestion for the crudded up vent hoses...While pumping the tank out, I use the fresh water hose from the marina, and squirt in water at the holding tank vent, while the tank is being pumped out. This accompishes two things: It clears the vent of any of the 'crud' in there, giving you a nice "sucking-air" sound to verify that this hose is indeed clear of debris...and it provides a small amount of water into the tank, from another direction. That will clean it better I expect.

Cheers,

Larry

K_LeMans · Post by **K_LeMans** » Sep 9th, '11, 11:01

Great suggestion about back flushing the vent after a pump-out.

Is your vent the OEM item, or did you replace?
If replacement, whose part (manufacturer) did you use?

Thanks!

Larry DeMers · Post by **Larry DeMers** » Sep 13th, '11, 16:43

Mine is a chrome plated little shell shaped vent that exists out the side of the boat. It is within reach of the pump-out on deck, so it is easy to reach down and spray water in that vent fitting. I was not able to find it shown at WM or Def., but they are always showing up when I don't need them (?!!??)..but it is the same vent that I got with the boat back in 1991. I doubt that the P.O. changed it out.

Larry

Terry · Post by **Terry** » Sep 14th, '11, 12:24

There's an interesting article in this month's Good Old Boat magazine on a home brew vent made from PVC and charcoal filtering. Not stainless or brass, but I suppose it could be gold-leafed.

I always thought a real marine head would be nice, and eliminate hauling the portahead to the marina bathroom. But reading some of headaches that marine heads produce, I'm sorta happy with my pour-out system.

Regards, Terry

Ben Coombs · Post by **Ben Coombs** » Sep 24th, '11, 08:24

I am going the other way... Our portable toilet stinks rather badly when used. And since there is no opening port hole(or any port hole) in the head, the smell lingers longer than we'd like. Also since three of us use the head, a two night trip can fill up the holding tank!

So I want to reinstall the marine head with a pump out only option... I just don't want to put our waste in the ocean. I have that good old boat article regarding the filter... But what is the best deck fitting? And where should it live? I was hoping I could fit the vent between stays to keep my toes from catching it. Anybody else add a pump out option to their 25? How big a tank? Can the vent be run through the hull at the toerail? Or must it be on deck?

Winter projects here I come![/quote]

sfreihofer · Post by **sfreihofer** » Sep 25th, '11, 01:01

I installed a head on my CD 25, but could only fit a 9 gallon holding tank in the space available. All head discharge goes to the tank, but I incorporated an optional overboard dump as well as a pump-out through a Y valve. I'm not happy with the venting I had incorporated, and since I had to remove the holding tank to install other hardware (dining table) I decided it's a good time to improve the venting before I reinstall the holding tank.

My boat has not been launched, so I have not used the head yet and am trying to decide on the best options. On a CD25, space is always a limitation.

There are two 1/2" vent openings into the tank, which I had tied together into one 1/2" hose. I don't think this is adequate venting.

I now intend to run both individual 1/2" vents through a common carbon filter of much larger diameter (thanks to the recent article in Good Old Boat magazine). I'm wondering now if it is necessary to vent the tank outboard, or if I can just vent it into the cabin through the filter? I don't know if the carbon filter is efficient enough at eliminating odors to allow this option. If not, I will have to determine the best option for a external vent... either through the cabin top or side.

I appeal to the wisdom of the users of this board to offer suggestions and/or advice.

You can see the installation at http://www.reefroof.com/restinterior.htm and http://www.reefroof.com/interiordone.htm

These photos may be helpful to you, Ben, in configuring your head installation, although they do not reflect the venting changes I am contemplating.

Stan Freihofer
1981 CD 25 #794
Ft. Lauderdale
www.ReefRoof.com

Ben Coombs wrote:I am going the other way... Our portable toilet stinks rather badly when used. And since there is no opening port hole(or any port hole) in the head, the smell lingers longer than we'd like. Also since three of us use the head, a two night trip can fill up the holding tank!

So I want to reinstall the marine head with a pump out only option... I just don't want to put our waste in the ocean. I have that good old boat article regarding the filter... But what is the best deck fitting? And where should it live? I was hoping I could fit the vent between stays to keep my toes from catching it. Anybody else add a pump out option to their 25? How big a tank? Can the vent be run through the hull at the toerail? Or must it be on deck?

Winter projects here I come!

[/quote][/url]

Ben Coombs · Post by **Ben Coombs** » Oct 13th, '11, 21:04

I have seen your boat before while perusing the board... You have done a great job!

I am going to stick with the pump out only, as we hug the coast most of the time. I also have pump out stations everywhere we go. The venting is still the hole in my planning... but I have some fledgling ideas about it.

My other big concern is the tank. I have found a web site that sells waste tanks (along with many other tanks) and they will put the fittings wherever you'd like them located. So I think that a larger 1" vent would be a good start. The intake from the head a regular 1.5" also on the top. The outlet, however could be located on the bottom, and make for some very complete pump outs... It seems that the Todd tanks need a tube extending to the bottom of the tank, that would seem to always leave a bit of waste in the bottom. Does a bottom outlet risk a seeping stench?

I have the whole winter to figure it out.... Just unstepped the mast and moved the boat to the yard for hauling. In fact I sadly have to venture out into the rain to get the jack stands out to the driveway. They are hauling tomorrow, or the 25th... and if I go to work with the stands in the back yard, they'll call at 10:30AM and be on their way. If I move them, then they'll be here the 25th. damned if you do.....

Jim Davis · Post by **Jim Davis** » Oct 14th, '11, 11:22

For your vents, let me suggest that two 1/2 inch are sufficient. They should be outside the hull, just below the hull/deck join and I try to have them facing in opposite directions to encourage air flow inside the tank. I do not put filters in because they restrict the circulation of air. As to connections to the tank itself, if at all possible they should be on the top to prevent any seepage. The little bit of poop left in the tank is a smaller consideration than a little bit of poop sneaking past the thread on the connector.

sfreihofer · Post by **sfreihofer** » Oct 15th, '11, 20:28

Jim;

Thanks for your suggestions. I understand your rationale.

I had originally joined the two 1/2" vents into a single 1/2" hose. I think that was a mistake, so I have now joined the two 1/2" vents into a single 3/4" vent, since the cross-sectional area of a 3/4" vent is more than the area of two 1/2" vents. This then leads to a 2" activated charcoal canister.

If I were to then run the vent through the hull below the deck, it would require a 1' downhill run, and would require even more hardware in an already overly congested area. It just doesn't seem practical. In order to vent outside the boat, it seems the only practical option is either through the cabin top or side.

For now, I am going to vent inside the boat, and see if the charcoal canister is efficient enough to allow this without an odor problem. If it turns out to be a problem, I will evaluate my options again.

Again, thanks for your advice. It is appreciated.

Stan Freihofer
1981 CD25 #794
S/V Pearl
Ft. Lauderdale

Steve Laume · Post by **Steve Laume** » Oct 16th, '11, 09:26

I seem to recall either Hinkley or Morris was running the vent line up inside of a stanchion. I don't know exactly how they accomplished this but it is a very creative approach to dealing with the vent problem.

I don't think that venting inside the boat is a very good idea, no matter what kind of filtering system is employed. Part of what is produced in and vented from the holding tank is methane gas. While you may be able to remove the odor, you would still be venting an explosive gas inside of your boat. Even if the quantities are very small, this just doesn't seem like a very good idea, Steve.

Ben Coombs · Post by **Ben Coombs** » Oct 16th, '11, 12:16

The venting through a stanchion sounds interesting, but involved. I am hoping to run it between the side stays, so that it can't intake any seawater, and can't hurt my feet when going forward in bare feet (my preferred method when the weather is warm).

The filter is a likely part of my plan, provided there is room for it. My other thought is to tee into the vent line and run a short section of pipe to a ball valve. When it's pump out time, I will open the ball valve to insure that there is always extra air available--I have heard that a blocked vent could be bad if the suction is too great.

Plastic-mart.com is the place where the custom tank configuration comes from. The lower fitting can be a welded in hose barb, so no threads to leak.. and I have never had a double clamped hose leak anything. I am a large fan of simple things too--they work better for longer. So I am inclined to try the bottom fitting. If it's not working there will be a chorus of Peeeuuuuuwww from my daughter up in the vee. I do love the summer when the boat is in the water, but there is fun to be had in the winter too! A freshened up bilge, and new pump... painted interior, electrical upgrades... and the waste system... and water system... better get that boat into the driveway!

sfreihofer · Post by **sfreihofer** » Oct 16th, '11, 17:11

Hey Steve;

The methane is something I hadn't considered. Hmmmmm. I guess I'll have to vent through the cabin side.

Thanks for the warning. This is the kind of thing that makes this forum invaluable.

Stan

sfreihofer · Post by **sfreihofer** » Oct 16th, '11, 18:17

Ben;

I think that no matter whether you put the fitting in the bottom or use a draw tube, there will always be a certain amount of sludge in the bottom of the tank. Maybe there will be a bit more with the draw tube, because it only extends to about 1/2" above the bottom.

I like the idea Larry offered for flushing the tank, but I'm not sure how to employ that idea with the filter canister in the vent line. That's another issue I will 'wait and see' about.

Good luck with your alterations. The head and holding tank has involved quite a bit of thought for me. It's an engineering challenge, and I'm no engineer. I'm not sure there is any perfect solution for all of the considerations involved. One of my biggest problems I have is limited space.

As for pumpout only, my holding tank is too small to eliminate the option for an overboard dump. It is a 9 gallon tank, but allowing for 45 degrees of heel before the tank contents back up into the vent line, there are only 6 gallons of usable tank volume. I don't yet know how many flushes that represents, but it can't be many.

Stan

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