Bad smell from holding tank vent

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   Lately I've noticed a bad odour coming from the holding tank vent (starboard transom) when someone pumps the head into the holding tank.  It's almost as though the line has a bit of a clog in it that is enough to seal the tank except when pumping the head into it, then causing the tank to burp some air out the vent aft.   In 6 years with this boat, I've never noticed this before.
Prior to me starting to pull hoses to check for clogs etc I thought I'd post here to see if there's a simple cause/solution to this problem that I may be missing?

Also, if I am to replace the waste hose from the head to the tank, what do people recommend? 

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Winner Members Profile Send Private Message Find Members Posts Add to Buddy List Commodore Joined: 07 September 2011 Status: Offline Points: 222	Post Options Post Reply Quote Winner Report Post Thanks(0) Quote Reply Topic: Bad smell from holding tank vent Posted: 13 July 2017 at 11:42pm
	Lately I've noticed a bad odour coming from the holding tank vent (starboard transom) when someone pumps the head into the holding tank. It's almost as though the line has a bit of a clog in it that is enough to seal the tank except when pumping the head into it, then causing the tank to burp some air out the vent aft. In 6 years with this boat, I've never noticed this before. Prior to me starting to pull hoses to check for clogs etc I thought I'd post here to see if there's a simple cause/solution to this problem that I may be missing? Also, if I am to replace the waste hose from the head to the tank, what do people recommend?
	Chris Eclipse #240 Thunder Bay, ON

fatjohnz Members Profile Send Private Message Find Members Posts Add to Buddy List Commodore Joined: 05 August 2006 Location: United States Status: Offline Points: 304	Post Options Post Reply Quote fatjohnz Report Post Thanks(0) Quote Reply Posted: 14 July 2017 at 6:32am
	I notice odor when the holding tank gets ... let's say ... ready for a pumpout. You can use Auqa-Chem or bleach but I find a pumpout the best cure. Also, I run a lot of clean water thru the head periodically. My input hose leads to a bucket instead of the thru hull so its easier to prime... I replaced my head hose with a thick walled marine sanitation hose... double clamps. john

Winner Members Profile Send Private Message Find Members Posts Add to Buddy List Commodore Joined: 07 September 2011 Status: Offline Points: 222	Post Options Post Reply Quote Winner Report Post Thanks(0) Quote Reply Posted: 14 July 2017 at 9:01am
	I checked and it's about 3/4 full right now. Was planning to pump it out soon anyway so we'll see if that helps.
	Chris Eclipse #240 Thunder Bay, ON

Bill Layton Members Profile Send Private Message Find Members Posts Add to Buddy List Commodore Joined: 15 September 2002 Location: Canada Status: Offline Points: 551	Post Options Post Reply Quote Bill Layton Report Post Thanks(0) Quote Reply Posted: 14 July 2017 at 9:13am
	If a holding tank gets too full it can clog up the vent hose or even the vent fitting itself. You would have to take those components apart to clean them out. Also if it is a bad smell it's because you are not using enzymes. This stuff works incredibly well and it's cheap, so be sure to use them. fatjohnz has mentioned the correct hose to use... never use corrugated hose for the toilet or holding tank. Double clamping a must and use sealant on the hose where it gets clamped to fittings.

bal149 Members Profile Send Private Message Find Members Posts Add to Buddy List Skipper Joined: 14 August 2010 Location: canada Status: Offline Points: 67	Post Options Post Reply Quote bal149 Report Post Thanks(0) Quote Reply Posted: 14 July 2017 at 11:24pm
	temporary fix of smelly lines and connections is Saran Wrap-keeps the freshness in and odours out and yes I am serious.

frfletch Members Profile Send Private Message Find Members Posts Add to Buddy List Commodore Joined: 13 May 2008 Location: Canada Status: Offline Points: 365	Post Options Post Reply Quote frfletch Report Post Thanks(0) Quote Reply Posted: 16 July 2017 at 1:08pm
	Chris. At 3/4 full it is time to go. You don't want to be sailing around with a septic tank on board. Nine gallons of liquid weighs about 70 lbs. That's behind the engine and adds to an already stern heavy boat. Just look at how her waterline sits when static. Get it out. Meanwhile, yes on the enzymes treatments. Regarding a smell from the vent when people flush, that is a good sign. You can't expect the gases remaining in those few cubic inches of air on top of 9 gallons of sewage to smell good. So when someone flushes, that air has to go somewhere. What is bad is when little insects, tiny spiders and such, build their nests in your vent outlet and plug it up, then the air can't get to the outside. The gases themselves on the inside of the tank expand with fermentation and when you start hearing bubbles coming back up from the toilet, and there is no smell from the vent, then you will also note that your boat stinks. Another thing, adding to what Bill said, make sure that there is no sag in the vent hose between the top of the tank and the vent. Otherwise you risk getting sewage in the vent hose and nothing short disconnecting that hose and draining it out, all while lying on your back in a very uncomfortable place, will be the only cure.

Winner Members Profile Send Private Message Find Members Posts Add to Buddy List Commodore Joined: 07 September 2011 Status: Offline Points: 222	Post Options Post Reply Quote Winner Report Post Thanks(0) Quote Reply Posted: 17 July 2017 at 11:52pm
	A pump out is on the agenda very soon. I'm surprised it has filled up this quickly this year. So today I checked the vent hoses for both the holding tank and the fuel tank. The fuel tank one is much easier so I did that first. Removing from the tank end, I blew into it and diesel was indeed expelled from the stern vent. Not tons, but some. The issue with this line is that it's impossible to get an upward run of the line as it leaves the tank because it runs underneath the quarter berth cushion. Anyone have any bright ideas on this one? Best I can figure is to zip strap it to the top of the incoming fuel hose. The holding tank vent is harder because you must crawl back on the starboard side to the stern and remove the panel covering the aft portion of the holding tank to access the barbed fitting the hose connects to. I removed the line from the tank as well as the hull fitting, removed the hose from the boat and flushed it with fresh water. There was indeed sewage in the line. Again, not much, but some. Reinstalled and in this case, because the line comes off the top of the holding tank it is possible to keep the line up higher (no sag) to prevent sewage flow up the line. I ended up running the line upwards to the bilge pump area, then back down to the hull fitting. Wednesday I'll pump out and hopefully will be good to go. Another piece of info learned about the Laser 28!
	Chris Eclipse #240 Thunder Bay, ON

Bill Layton Members Profile Send Private Message Find Members Posts Add to Buddy List Commodore Joined: 15 September 2002 Location: Canada Status: Offline Points: 551	Post Options Post Reply Quote Bill Layton Report Post Thanks(0) Quote Reply Posted: 18 July 2017 at 8:51am
	I have seen the holding tank vent get plugged many times. The installed vents are actually designed for fuel only (you cannot buy them for holding tanks alone) this means they have spark arrestor screens on them which get clogged. I remove the screen on them and have even drilled them out so that the hole in them for venting is less restricted. You have to remove the vent to do this effectively. The fuel vent you can tie-rap the hose and screw it to just under the wood cleat that supports the cushion. Then at the end of that engine panel it goes straight up to the vent tightly and it eliminates that problem. It works so well you can fill your fuel tank at full speed afterwards, a much better system. You can remove the screen arrestor for the fuel as well because the arrestor screen is for gasoline only. Diesel cannot ignite even if you try to light it with a lighter. Diesel needs to be atomised into a fine mist in order to ignite and that only happens in the cylinder. This is why Diesel equipped boats do not need engine compartment evacuation fans. Edited by Bill Layton - 18 July 2017 at 8:55am

frfletch Members Profile Send Private Message Find Members Posts Add to Buddy List Commodore Joined: 13 May 2008 Location: Canada Status: Offline Points: 365	Post Options Post Reply Quote frfletch Report Post Thanks(0) Quote Reply Posted: 18 July 2017 at 11:47am
	Well done Chris. Next time however, you only need to get to the end of the vent hose at the vent end. any liquid in the hose owing to a sag in that line can be tipped up and will drain back into the tank. If you had anything in there at all, then that will be 99% likely to have been the problem because gasses can't get past any solid in the line. I have a short piece of 1/2" hose that I just stick onto the vent when I'm checking it, lying so comfortably in that cozy spot with my 1/2 kilo of spinal hardware being stretched over the transverse stringer in that area, then I can blow throw the vent with a clean line. For some reason, disconnecting from the top of the tank and blowing on that line through the vent doesn't appeal to me. I have done the same as Bill suggests on the waste vent by taking out the screen and then drilling out the inside of the vent to get more flow area. The inside of a 1/2" barb is only a little over 1/4" ID and combined with the 90 degree bend in that fitting gives it a very restricted flow. That "its-bitsy-spider" your mother told you about does indeed go up the spout, unlike what she said.....it doesn't come back out. It builds its home there and raises a family. I know, I know.....its a dumb place to build a home, but the same species got the crap beat out of it with a spoon by moving to close and sitting next to Little Miss Muffet. Not too smart!

Winner Members Profile Send Private Message Find Members Posts Add to Buddy List Commodore Joined: 07 September 2011 Status: Offline Points: 222	Post Options Post Reply Quote Winner Report Post Thanks(0) Quote Reply Posted: 18 July 2017 at 4:28pm
	I hear ya Frank, although with this being my first time I wanted to make good and sure the line was clean and flushed so decided to remove the whole thing. Having done it once, next time (which hopefully there isn't one), I'll just remove from the aft end. Regarding the wire mesh, I actually tried removing the vent fitting from the hull but it seems pretty firmly in there. Is there a trick or once the hose is removed and the nut/washer is off do you just push it through? Is the wire mesh on the barb end or the "hole" end of the vent?
	Chris Eclipse #240 Thunder Bay, ON

Bill Layton Members Profile Send Private Message Find Members Posts Add to Buddy List Commodore Joined: 15 September 2002 Location: Canada Status: Offline Points: 551	Post Options Post Reply Quote Bill Layton Report Post Thanks(0) Quote Reply Posted: 19 July 2017 at 11:21pm
	I usually poke a screw driver thru it and the whole screen pops out in one piece. Then I do the drilling. and re-install the vent without the black rubber O-ring that came with some of them.

frfletch Members Profile Send Private Message Find Members Posts Add to Buddy List Commodore Joined: 13 May 2008 Location: Canada Status: Offline Points: 365	Post Options Post Reply Quote frfletch Report Post Thanks(0) Quote Reply Posted: 24 July 2017 at 11:07pm
	Chris, If the vent was sealed in with something like 5200 it may be a little reluctant to come out. You can try using a heat gun or hair dryer to soften the 5200, then push it out...........or use a rubber mallet and beat it out from the inside after removing the nut.