Holding tank vent locations

[AusCan]

Folks - in my 1989 CPMY (California model) the only small breather outlets of the types described here in this thread, are the water and one for each of the diesel tanks.. i.e. i have three of them, with the two diesel ones in close proximity of the diesel filler caps.

Before I hunt down and try trace these is there any scenario where the holding tank may share the breather from say the diesel tank?

No chance. ummm Well ,maybe 1%.

Follow your hoses, trace your lines. Its the only way to really get friendly and intimate with your boat. She'll love you for it.

Your holding tank may have a larger breather hose with a 1 1/2" thru hull.

 

[triatica]

Thanks - yes, we are about to do that starting tomorrow. Good to know the chances of that configuration would be so small.

 

[HeadMistress]

No...at least I fervently hope not!
Start your search on the hull near the deck pumpout fitting. If the tank was an OEM installation, that thru-hull is likely to be identical to the water and fuel vent thru-hulls. It'll be larger and/or have a different thru-hull only if the tank was installed by a PO.

--Peggie

 

[Comodave]

They should absolutely never be combined, but who knows what some random builder or PO did...

 

[Bacchus]

Folks - in my 1989 CPMY (California model) the only small breather outlets of the types described here in this thread, are the water and one for each of the diesel tanks.. i.e. i have three of them, with the two diesel ones in close proximity of the diesel filler caps.

Before I hunt down and try trace these is there any scenario where the holding tank may share the breather from say the diesel tank?

Is it possible a PO installed a mushroom type thru hull and maybe a clam shell covering if they were concerned with water intrusion?
Personal opinion... it's a good idea for everyone to investigate ALL hull penetrations and know where they are attached to. Memory gets foggy - draw a diagram and mark locations and label the diagram and interior hulls if visible, with the source info.

If you can access the holding tank vent disconnect it and blow compressed air through it... ensures it is open and not blocked and should help locating it outside.

 

[The Brockerts]

I would not think so. ABYC probably would not allow that. And if they did how would it work?. What appends when your holding tank backups in the vent hose and feeds that into a diesel tank?
Look around, you will find them. I went looking not once, not twice but for hours on different days until I tracked down each hose.

 

[triatica]

OK - mystery solved, the vent goes back to the centerline of the vessel and then heads along the gap between the genset and bulkhead forward of that to exit in about a 1" skin fitting close to the exhaust of the genset on the starboard side about 8 inches above the waterline..

So firstly I did not expect such a large exit and was looking for something like the smaller fuel tank breather... on the other hand I am delighted we have such a generous diameter hose doing this job. There were some depressions in the horizontal section which needed to be blown out with air and then fastened so there there are no lower sections... of some suspicion is a tight corner which pinched the hose a little.

Anyways, thanks for the support on this topic.

 

[Bare Necessities]

I realize this is an old post but I just came across it. I have the same boat except a 1989. Only one of the vents on the side is hooked to the vent line. My vent line was plugged as well. My holding tank is in the aft cabin floor port side. One hatch lets you see the sending unit and the hatch forward of that one gives access to the lines going to the tank and also the vent line. There was no filter on mine but it had been over filled and mess was allowed to sit in the vent line and dried life concrete. I had to use a drill to drill open the small port on the tank and replaced about 2' of the line that was clogged, all is well now. Hope you already have your fixed but if you need to know more reach out to me. The second vent on mine is just a spare. Charlie

 

[The Brockerts]

Charlie,
Thanks for the note. I've ripped out everything, tanks, hoses, filters, and replaced it with new. I did plumb in a special vent line/value so when pumping out there won't be any issues. I'll keep my eyes out on your posts as I'm sure we share some of the same problems. Current update going on is the master A/C/Heater. Putting in an all in one A/C with it's own pump, filter, thru hull, so when one system goes down, I can still heat and cool. Moving onboard full time in 1 month.

The Brockerts

 

[Bare Necessities]

I realize this is an old post but I just came across it. I have the same boat except a 1989. Only one of the vents on the side is hooked to the vent line. My vent line was plugged as well. My holding tank is in the aft cabin floor port side. One hatch lets you see the sending unit and the hatch forward of that one gives access to the lines going to the tank and also the vent line. There was no filter on mine but it had been over filled and mess was allowed to sit in the vent line and dried life concrete. I had to use a drill to drill open the small port on the tank and replaced about 2' of the line that was clogged, all is well now. Hope you already have your fixed but if you need to know more reach out to me. The second vent on mine is just a spare. Charlie

 

[Bare Necessities]

Sorry, I see I hit post twice on my last post. I am curious, where are you mounting the new a/c system? I still have 3 split units and wondered about the all in one units but so far mine are doing good. Good luck on your project.