CD 33 Holding Tank Vent

[rghinson]

I am a new CD33 owner. The boat is great but reeks of sewer gas. I have replaced all the hoses for the head and tank but suspect that the vent for the tank is clogged. There are two vents on the transom. I suspect that one is for the fuel tank and the other is for the holding tank. I want to back flush the holding tank vent (but obviously not the fuel tank vent) so which is which?

Thanks,

Reid Hinson
CD33 First Star
Oriental, NC

[Jim Davis]

Reid

Be very careful when back flushing a vent. This is especially true of the holding tank. You do not want to over pressure it and cause a leak, or worse.

When I have doubts about the vent I start by inspecting the entire hose and removing it from the vent fitting. Then I clean the fitting itself. I reinstall the hose and try to blow it out from the tank end. One other thing you want to try and eliminate any low spot that will act as a trap for liquid, or worse. If at all possible two vents are much better than one - I know that manufacturers only put one in, but then they don't have to live with a smelly tank.

Here is a long read, you need to go near the end for odor control.
http://boatbuilding.com/article.php/Mar ... vsFolklore

Good luck

[Zeida]

Reid... the holding tank vent is the one on the stern port side. Mine was also clogged when I first got the boat. I finally got myself inside the lazarette, disconnected the small hose that clamps directly into that small vent and made sure it worked. Have never had the "smell" again.

I also changed all the hoses related to that holding tank and macerator pump. I keep a very clean tank. Good luck.

[rghinson]

Thank you very much for your replies!!
Very helpful.

Reid Hinson
CD33 First Star
Oriental, NC

[Jeff and Sarah]

Reid,

If you do decide to back flush the vent, be sure to chase the lines on your boat first rather than assuming all 33's were made the same. The port side makes sense because the diesel tank is on the starboard side, but you never know what weird changes former owners have made. It would be awful to accidentally send water in to your diesel tank for no good reason.

I also need to replace my vent line. The smell is quickly making the project a higher and higher priority.

Jeff

[rperrone]

Just as Bandolero. PAISAN's holding tank vent is on the Port side.
Fuel tank vent is on Starboard side.

Easy to trace and route line back to tanks from hull venst.
Run new hose for the holding tank. Make sure vent screens are clear. After disconnecting hose, put compresed air on the screen to blow it clear.

[Ben Thomas]

Although the CD30 is set up differently the holding tank only had one vent coming out starboard side from V-berth area just below toe rail. After replacing all the hose's it still had some serious stank. I added a second vent that comes out the port side hull opposite the first vent which created a cross ventilation action. The original vent exits from forward stb.top of tank, the second vent exits aft port top of tank. Both snake through the chain locker and up to exit point near toe rail.
So far so good.

[K_LeMans]

I haven't had any odor issue, but the last time I had the holding tank pumped out, I heard a hissing noise which turned out to be coming from the head itself. It appears that the vent line is clogged and so the vacuum created by evacuating the holding tank was actually drawing air through the head.

Anyone else ever had this experience?

[tmsc]

I have had the same problem and normally make sure I have the seat (lavac) up wile pumping out the holding tank. The vent cannot keep up with the pumps some places have. I also have constant problems with the flame screens on the vent fittings clogging. I recently replaced all three of the transom vents with vents from WM that were supposed to be stainless steel, but turned out they were just that chrome plated zinc junk. That just makes the problem worse due to corrosion of the fitting. In the near future, I will be replacing the holding tank vent with a normal thru hull and replacing the remainder with bronze tank vents.

[Jim Davis]

This is Classic Vent Blockage. If it were me, I would take the hose off the vent fitting and clear it then reattach the hose and try blowing the hose out from the tank end. Back pressure from the vent fitting end can cause over pressure on the tank with "spectacular" results. You can also over pressure by flushing a head with clogged vent(s).

[K_LeMans]

Lee, let us know where you get the bronze tank vents........
Thanks!

[Paul D.]

Our holding tank vent is also on the stern port side. Fuel vent on Strbd.

I would clean out screen at vent, detach from holding tank and blow out from tank side. I too try to keep a clean tank and flush very clean at the end of season inspecting and sometimes hosing out from the inspection port.

Good luck.

[Zeida]

Kevin... you can order the bronze stern tank vents from Spartan Marine, item V100PB. They are gorgeous when brand new.

[Dick Kobayashi]

I had this problem and solved it by using a portion of bent clothes hanger to remove some of the crud in the vent fitting. I got enough out in a minute or two to get adequate air flow. However that fact that the holding tank system had been slightly pressurized for a while impregnated the head to tank hose with "whiff of tank" so later I replaced that hose.